The Carelon Clinical Appropriateness Guidelines (hereinafter “the Carelon Clinical Appropriateness Guidelines” or the “Guidelines”) are designed to assist providers in making the most appropriate treatment decision for a specific clinical condition for an individual. The Guidelines establish objective and evidence-based criteria for medical necessity determinations, where possible, that can be used in support of the following:

To establish criteria for when services are medically necessary
To assist the practitioner as an educational tool
To encourage standardization of medical practice patterns
To curtail the performance of inappropriate and/or duplicate services
To address patient safety concerns
To enhance the quality of health care
To promote the most efficient and cost-effective use of services

The Carelon guideline development process complies with applicable accreditation and legal standards, including the requirement that the Guidelines be developed with involvement from appropriate providers with current clinical expertise relevant to the Guidelines under review and be based on the most up-to-date clinical principles and best practices. Resources reviewed include widely used treatment guidelines, randomized controlled trials or prospective cohort studies, and large systematic reviews or meta-analyses. Carelon reviews all of its Guidelines at least annually.

Carelon makes its Guidelines publicly available on its website. Copies of the Guidelines are also available upon oral or written request. Additional details, such as summaries of evidence, a list of the sources of evidence, and an explanation of the rationale that supports the adoption of the Guidelines, are included in each guideline document.

Although the Guidelines are publicly available, Carelon considers the Guidelines to be important, proprietary information of Carelon, which cannot be sold, assigned, leased, licensed, reproduced or distributed without the written consent of Carelon.

Carelon applies objective and evidence-based criteria, and takes individual circumstances and the local delivery system into account when determining the medical appropriateness of health care services. The Carelon Guidelines are just guidelines for the provision of specialty health services. These criteria are designed to guide both providers and reviewers to the most appropriate services based on a patient’s unique circumstances. In all cases, clinical judgment consistent with the standards of good medical practice should be used when applying the Guidelines. Guideline determinations are made based on the information provided at the time of the request. It is expected that medical necessity decisions may change as new information is provided or based on unique aspects of the patient’s condition. The treating clinician has final authority and responsibility for treatment decisions regarding the care of the patient and for justifying and demonstrating the existence of medical necessity for the requested service. The Guidelines are not a substitute for the experience and judgment of a physician or other health care professionals. Any clinician seeking to apply or consult the Guidelines is expected to use independent medical judgment in the context of individual clinical circumstances to determine any patient’s care or treatment.

The Guidelines do not address coverage, benefit or other plan specific issues. Applicable federal and state coverage mandates take precedence over these clinical guidelines, and in the case of reviews for Medicare Advantage Plans, the Guidelines are only applied where there are not fully established CMS criteria. If requested by a health plan, Carelon will review requests based on health plan medical policy/guidelines in lieu of the Carelon Guidelines. Pharmaceuticals, radiotracers, or medical devices used in any of the diagnostic or therapeutic interventions listed in the Guidelines must be FDA approved or conditionally approved for the intended use. However, use of an FDA approved or conditionally approved product does not constitute medical necessity or guarantee reimbursement by the respective health plan.

The Guidelines may also be used by the health plan or by Carelon for purposes of provider education, or to review the medical necessity of services by any provider who has been notified of the need for medical necessity review, due to billing practices or claims that are not consistent with other providers in terms of frequency or some other manner.

General Clinical Guideline

Clinical Appropriateness Framework

Critical to any finding of clinical appropriateness under the guidelines for a specific diagnostic or therapeutic intervention are the following elements:

Prior to any intervention, it is essential that the clinician confirm the diagnosis or establish its pretest likelihood based on a complete evaluation of the patient. This includes a history and physical examination and, where applicable, a review of relevant laboratory studies, diagnostic testing, and response to prior therapeutic intervention.
The anticipated benefit of the recommended intervention is likely to outweigh any potential harms, including from delay or decreased access to services that may result (net benefit).
Widely used treatment guidelines and/or current clinical literature and/or standards of medical practice should support that the recommended intervention offers the greatest net benefit among competing alternatives.
There exists a reasonable likelihood that the intervention will change management and/or lead to an improved outcome for the patient.

Providers may be required to submit clinical documentation in support of a request for services. Such documentation must a) accurately reflect the clinical situation at the time of the requested service, and b) sufficiently document the ordering provider’s clinical intent.

If these elements are not established with respect to a given request, the determination of appropriateness will most likely require a peer-to-peer conversation to understand the individual and unique facts that would justify a finding of clinical appropriateness. During the peer-to-peer conversation, factors such as patient acuity and setting of service may also be taken into account to the extent permitted by law.

Simultaneous Ordering of Multiple Diagnostic or Therapeutic Interventions

Requests for multiple diagnostic or therapeutic interventions at the same time will often require a peer-to-peer conversation to understand the individual circumstances that support the medical necessity of performing all interventions simultaneously. This is based on the fact that appropriateness of additional intervention is often dependent on the outcome of the initial intervention.

Additionally, either of the following may apply:

Current literature and/or standards of medical practice support that one of the requested diagnostic or therapeutic interventions is more appropriate in the clinical situation presented; or
One of the diagnostic or therapeutic interventions requested is more likely to improve patient outcomes based on current literature and/or standards of medical practice.

Repeat Diagnostic Intervention

In general, repeated testing of the same anatomic location for the same indication should be limited to evaluation following an intervention, or when there is a change in clinical status such that additional testing is required to determine next steps in management. At times, it may be necessary to repeat a test using different techniques or protocols to clarify a finding or result of the original study.

Repeated testing for the same indication using the same or similar technology may be subject to additional review or require peer-to-peer conversation in the following scenarios:

Repeated diagnostic testing at the same facility due to technical issues
Repeated diagnostic testing requested at a different facility due to provider preference or quality concerns
Repeated diagnostic testing of the same anatomic area based on persistent symptoms with no clinical change, treatment, or intervention since the previous study
Repeated diagnostic testing of the same anatomic area by different providers for the same member over a short period of time

Repeat Therapeutic Intervention

In general, repeated therapeutic intervention in the same anatomic area is considered appropriate when the prior intervention proved effective or beneficial and the expected duration of relief has lapsed. A repeat intervention requested prior to the expected duration of relief is not appropriate unless it can be confirmed that the prior intervention was never administered. Requests for on-going services may depend on completion of previously authorized services in situations where a patient’s response to authorized services is relevant to a determination of clinical appropriateness.

Imaging of the Abdomen and Pelvis

General Information/Overview

Scope

These guidelines address advanced imaging of the abdomen and pelvis in both adult and pediatric populations. For interpretation of the Guidelines, and where not otherwise noted, “adult” refers to persons age 19 and older, and “pediatric” refers to persons age 18 and younger. Where separate indications exist, they are specified as Adult or Pediatric. Where not specified, indications and prerequisite information apply to persons of all ages.

See the Coding section for a list of modalities included in these guidelines.

Technology Considerations

Advanced imaging is an umbrella term that refers to anatomy-based (structural), physiology-based (functional), and hybrid imaging methods that offer greater spatial and/or contrast resolution relative to conventional imaging methods in radiology such as radiography or ultrasound. Examples of advanced structural imaging include computed tomography (CT) and magnetic resonance imaging (MRI) and some technique variants. Advanced functional imaging includes nuclear medicine and molecular imaging techniques such as scintigraphy, single photon emission computed tomography (SPECT), and positron emission tomography (PET) as well as those MRI/CT technique variants that create image contrast based on a physiological parameter (for example, functional magnetic resonance imaging (fMRI). Hybrid advanced imaging techniques optimize diagnostic accuracy by coupling structural and functional approaches (such as PET-CT or PET-MRI).

Ultrasound is the initial imaging modality of choice for many conditions of the abdomen and pelvis, including hepatobiliary, urinary tract, and gynecologic conditions. While ultrasound is operator dependent and image quality may be impacted by obesity and bowel gas, accuracy, availability and absence of ionizing radiation make it an ideal choice for initial evaluation of several intra-abdominal conditions, especially in the right upper quadrant and in the pelvis and especially in pediatric patients and pregnant women.

Computed tomography (CT) is often utilized for imaging the abdomen and pelvis. It provides excellent 3-dimensional resolution and can be performed relatively quickly, reducing the potential for motion artifact. A major drawback of CT is the dose of ionizing radiation required for image acquisition, which is of particular concern in younger patients and those who require multiple scans over time.

CT may be performed with or without contrast; contrast provides additional detail to delineate vascular and gastrointestinal structures and is recommended in certain settings, such as infection, tumor, hemorrhage and visceral lesions. However, contrast increases scan acquisition time, and confers risk in cases of impaired renal function, pregnancy, metformin use, radioactive iodine treatment for thyroid disease, or previous reactions to contrast agents. Noncontrast CT may often suffice in some situations, and is preferred when evaluating for intra-abdominal hemorrhage and/or calcification.

Magnetic resonance imaging (MRI) requires a longer time for image acquisition and is more prone to motion artifact than CT. However, MRI does not expose patients to ionizing radiation and has better contrast resolution than CT. MRI may be a useful substitute in cases where contrast CT is contraindicated. It is often preferred in pediatric patients due to the absence of radiation; however, sedation may be required in younger patients in order to obtain adequate images.

MRI may be performed with or without contrast. Use of contrast is recommended for imaging of vascular structures or solid organs. The most commonly used agent for contrast MRI is gadolinium, but iron oxide and iron platinum contrast agents are also available. Administration of gadolinium has been associated with a rare but serious condition known as nephrogenic systemic fibrosis, and should be avoided in persons with advanced renal disease. Gadolinium contrast has also recently been shown to accumulate within the brain parenchyma, a finding of uncertain clinical significance.There are a number of alternative contrast agents which have been developed for specialized use including gadoxetic acid (hepatobiliary imaging), gadofosveset (a blood pool agent), and gadobutrol (an extracellular fluid agent).

The use of contrast is at the discretion of the ordering provider and/or the radiologist performing the imaging study, and should be tailored to the individual circumstances of each case.

Magnetic resonance cholangiopancreatography (MRCP) is a noninvasive alternative to endoscopic retrograde cholangiopancreatography (ERCP). MRCP avoids the risks associated with anesthesia and does not expose patients to ionizing radiation. It is able to detect extraductal abnormalities and can provide better visualization of structures proximal to a ductal obstruction. However, it is prone to motion artifact, may be less able to detect subtle abnormalities, and—unlike ERCP—has no therapeutic capabilities.

Dynamic pelvic MRI yields a 3-dimensional image used to evaluate the pelvic floor and rectal function by imaging pelvic muscles at rest and while contracted. Magnetic resonance defecography is a form of dynamic MRI used for evaluation of pelvic organ and muscle function through imaging stages of defecation. Dynamic pelvic MRI may be indicated in cases of pelvic organ prolapse, pelvic pain, and fecal and urinary incontinence.

CT enterography and MR enterography are noninvasive, cross-sectional imaging modalities protocolled to optimize visualization of the small intestine. CT enterography provides images of the entire small intestine without interference from overlapping loops, and detects both extraluminal and luminal disease. MR enterography also provides high-contrast resolution; it can detect abscesses and fistulas, and can distinguish fibrotic from inflammatory structures. In general, CT enterography is preferred for extraluminal pathology, whereas MR enterography is preferred for organ-specific and disease-specific (such as Crohn’s disease) evaluation.

Imaging of the urinary tract often begins with kidney, ureter, and bladder (KUB) radiography. This type of radiograph is particularly useful in acute care settings for evaluation of diffuse pain, or pain suggestive of renal or urinary tract disease. Ultrasound is also useful for initial evaluation and avoids the risks associated with radiation exposure. Both ultrasound and KUB radiography may be used for follow-up of nephrolithiasis in select patients.

CT abdomen/pelvis stone protocol (CT KUB), a noncontrast CT scan that images the kidney, ureters, and bladder, is commonly used for visualizing the urinary tract. Indications for CT KUB include urolithiasis/nephrolithiasis, renal parenchymal calcifications, and exclusion of hemorrhagic changes. Low-dose CT can also be used to scan for urinary tract stones with a lowered effective radiation dose. Compared to standard CT, low-dose CT still has excellent sensitivity, but image resolution can suffer, especially in the case of urinary tract stones under 3 mm in size.

CT urography (CTU, also referred to as CT IVP or CT IVU) is a more complex variant of CT that is used to evaluate the urinary tract. While CT KUB is simply a noncontrast CT scan, CT urogram includes an initial noncontrast CT scan followed by contrast-enhanced nephrographic phase and excretory phase imaging. CT urogram combines conventional CT with thin-section axial CT images taken during the excretory phase. Historically, CT was combined with excretory urography (EU) for CT urogram, but this method is no longer standard. CT urogram can be used to evaluate various tumor types, papillary necrosis, and renal inflammatory disease, among other conditions.

Definitions

Phases of the care continuum are broadly defined as follows:

Screening – testing in the absence of signs or symptoms of disease
Diagnosis – testing based on a reasonable suspicion of a particular condition or disorder, usually due to the presence of signs or symptoms
Management – testing to direct therapy of an established condition, which may include preoperative or postoperative imaging, or imaging performed to evaluate the response to nonsurgical intervention
Surveillance – periodic assessment following completion of therapy, or for monitoring known disease that is stable or asymptomatic
Indeterminate lesion – focal mass or mass-like finding identified on prior imaging that has not been confidently diagnosed as either benign or malignant based on imaging appearance and/or biopsy
Cannot be performed or is nondiagnostic – applies when the test:
- Is positive or indeterminate for clinically significant pathology when the information provided about the abnormality by the test is not sufficient to direct subsequent management
- Is negative when the negative likelihood ratio of the test is both insufficient to confidently exclude the absence of suspected disease and unable to direct subsequent management. This typically applies in scenarios with moderate to high clinical pretest probability with negative testing or low pretest probability with clear evidence for net benefit
- Has been previously nondiagnostic because of a persistent clinical factor (e.g., body habitus, immobility) that is very likely to make retesting nondiagnostic as well
- Cannot be performed due to a medical contraindication (e.g., contrast nephrotoxicity, allergy, or in highly radiation sensitive populations such as pediatrics and pregnancy) or reasonable inavailability related to lack of local expertise or service availability.

Statistical terminology

Confidence interval (CI) – range of values which is likely to contain the cited statistic. For example, 92% sensitivity (95% CI, 89%-95%) means that, while the sensitivity was calculated at 92% on the current study, there is a 95% chance that, if a study were to be repeated, the sensitivity on the repeat study would be in the range of 89%-95%.
Diagnostic accuracy – ability of a test to discriminate between the target condition and health. Diagnostic accuracy is quantified using sensitivity and specificity, predictive values, and likelihood ratios.
Hazard ratio – odds that an individual in the group with the higher hazard reaches the outcome first. Hazard ratio is analogous to odds ratio and is reported most commonly in time-to-event analysis or survival analysis. A hazard ratio of 1 means that the hazard rates of the 2 groups are equivalent. A hazard ratio of greater than 1 or less than 1 means that there are differences in the hazard rates between the 2 groups.
Likelihood ratio – ratio of an expected test result (positive or negative) in patients with the disease to an expected test result (positive or negative) in patients without the disease. Positive likelihood ratios, especially those greater than 10, help rule in a disease (i.e., they substantially raise the post-test probability of the disease, and hence make it very likely and the test very useful in identifying the disease). Negative likelihood ratios, especially those less than 0.1, help rule out a disease (i.e., they substantially decrease the post-test probability of disease, and hence make it very unlikely and the test very useful in excluding the disease).
Odds ratio – odds that an outcome will occur given a particular exposure, compared to the odds of the outcome occurring in the absence of that exposure. An odds ratio of 1 means that the exposure does not affect the odds of the outcome. An odds ratio greater than 1 means that the exposure is associated with higher odds of the outcome. An odds ratio less than 1 means that the exposure is associated with lower odds of the outcome.
Predictive value – likelihood that a given test result correlates with the presence or absence of disease. Positive predictive value is defined as the number of true positives divided by the number of test positives. Negative predictive value is defined as the number of true negatives divided by the number of test negative patients. Predictive value is dependent on the prevalence of the condition.
Pretest probability – probability that a given patient has a disease prior to testing. May be divided into very low (less than 5%), low (less than 20%), moderate (20%-75%), and high (greater than 75%) although these numbers may vary by condition.
Relative risk – probability of an outcome when an exposure is present relative to the probability of the outcome occurring when the exposure is absent. Relative risk is analogous to odds ratio; however, relative risk is calculated by using percentages instead of odds. A relative risk of 1 means that there is no difference in risk between the 2 groups. A relative risk of greater than 1 means that the outcome is more likely to happen in the exposed group compared to the control group. A relative risk less than 1 means that the outcome is less likely to happen in the exposed group compared to the control group.
Sensitivity – conditional probability that the test is positive, given that the patient has the disease. Defined as the true positive rate (number of true positives divided by the number of patients with disease). Excellent or high sensitivity is usually greater than 90%.
Specificity – conditional probability that the test is negative, given that the patient does not have the disease. Defined as the true negative rate (number of true negatives divided by the number of patients without the disease). Excellent or high specificity is usually greater than 90%.

Clinical Indications

The following section includes indications for which advanced imaging of the abdomen and pelvis is considered medically necessary, along with prerequisite information and supporting evidence where available. Indications, diagnoses, or imaging modalities not specifically addressed are considered not medically necessary. For cancer screening guidelines and management of documented malignancy, please refer to the Oncologic Imaging guidelines.

It is recognized that imaging often detects abnormalities unrelated to the condition being evaluated. Such findings must be considered within the context of the clinical situation when determining whether additional imaging is required.

General Abdominal and Pelvic Indications

Congenital and developmental conditions, not otherwise specified

Advanced imaging is considered medically necessary for diagnosis and management.

IMAGING STUDY

ADULT

CT abdomen and/or pelvis
MRI abdomen and/or pelvis

PEDIATRIC

Ultrasound required for initial evaluation of hepatobiliary and genitourinary anomalies
Ultrasound recommended for initial evaluation of pancreatic anomalies
CT abdomen and/or pelvis when additional imaging is needed to guide treatment
MRI abdomen and/or pelvis when additional imaging is needed to guide treatment
MRI preferred for evaluation of uterine anomalies
MRCP preferred for evaluation of biliary and pancreatic duct anomalies

Rationale

A variety of advanced structural and functional imaging modalities may be needed in the diagnosis and management of select intra-abdominal congenital abnormalities. More common anomalies of the gastrointestinal system including pyloric stenosis, midgut volvulus, Hirschsprung’s disease, and small left colon syndrome are usually diagnosed with upper GI series or barium enema. Meckel’s scan is useful to diagnose ectopic functioning gastric mucosa, typically in a Meckel’s diverticulum ¹ and has moderate to high diagnostic accuracy in patients with subacute unexplained gastrointestinal bleeding.^2,3,4 Ultrasound is the initial modality for evaluation of congenital hepatobiliary disease.^{5, 6} Although it requires ionizing radiation, hepatobiliary scintigraphy has high specificity (greater than 98%) and moderate sensitivity (70%) for the diagnosis of biliary atresia with very large positive predictive value sufficient to establish the diagnosis.⁷ Renal scintigraphy can be useful to establish the diagnosis of congenital anomalies of the kidney and ureter ^{8, 9} or for differential estimation of renal function, especially in the presence of an ectopic, malrotated, or hypoplastic kidney.⁹

Infectious and inflammatory conditions including abscess– not otherwise specified

Advanced imaging is considered medically necessary for diagnosis and management.

IMAGING STUDY

CT abdomen and/or pelvis
MRI abdomen and/or pelvis

Rationale

CT or MRI is usually sufficient to evaluate for complications of intra-abdominal infection such as abscess; both modalities are widely available and commonly performed. However, factors such as distorted anatomy, ileus, ascites, and healing wounds can complicate the structural assessment of infection.¹⁰ When diagnostic uncertainty remains following CT and/or MRI, leukocyte scintgraphy may be helpful as an add-on test to further characterize suspected sites of infection such as infected surgical material including vascular grafts, shunts, or abscess.^10,11

Trauma, not otherwise specified

Advanced imaging is considered medically necessary for diagnosis and management.

IMAGING STUDY

CT abdomen and/or pelvis
MRI abdomen and/or pelvis when CT cannot be performed or is nondiagnostic

Tumor or neoplasm – not otherwise specified

For cancer screening guidelines and management of documented malignancy, please refer to the Oncologic Imaging guidelines.

Advanced imaging is considered medically necessary in EITHER of the following scenarios:

Evaluation of palpable abdominal or pelvic masses of indeterminate origin
Characterization of indeterminate lesions arising in the solid abdominal viscera and surrounding anatomic structures

IMAGING STUDY

ADULT

Ultrasound required for initial evaluation of a palpable pelvic mass in women
CT abdomen and/or pelvis for all other scenarios, or following nondiagnostic pelvic ultrasound
MRI abdomen for further characterization of abdominal mass seen on prior imaging, including CT scan

PEDIATRIC

Ultrasound required for initial evaluation of a palpable pelvic mass
Ultrasound recommended for initial evaluation of an abdominal mass
CT abdomen and/or pelvis for initial evaluation of a palpable abdominal mass, or following nondiagnostic ultrasound
MRI abdomen and/or pelvis for initial evaluation of a palpable abdominal mass, or following nondiagnostic ultrasound

Female Reproductive System and Obstetric Indications

Adenomyosis

Advanced imaging is considered medically necessary for diagnosis and management following nondiagnostic pelvic ultrasound.

IMAGING STUDY

MRI pelvis

Rationale

There is wide clinical agreement and support from multiple clinical guidelines for ultrasound as the initial imaging modality for evaluation of structural pathology within the reproductive organs of the female pelvis^12-15 with advanced imaging reserved in select cases as an add-on test to further characterize abnormalities on ultrasound or when ultrasound is nondiagnostic. MRI is the advanced imaging modality of choice due to its superior soft tissue contrast.^{14, 16}

Adnexal mass

Advanced imaging is considered medically necessary for diagnosis and management following nondiagnostic pelvic ultrasound.

IMAGING STUDY

MRI pelvis

Rationale

Endometriosis

Advanced imaging is considered medically necessary for diagnosis and management following nondiagnostic pelvic ultrasound.

IMAGING STUDY

MRI pelvis

Rationale

A review of 49 studies involving 4807 women was performed to determine whether imaging tests could be used as a replacement for diagnostic surgery or as a triage test to assist in decision making regarding diagnostic surgery. The evaluated modalities included ultrasound, MRI, and CT. While none of the imaging modalities met criteria to replace surgery in making the diagnosis of endometriosis, transvaginal ultrasound did approach the criteria for a triage test for pelvic endometriosis in general. Transvaginal ultrasound met the criteria for a triage test for endometrioma, as well as for deeply infiltrating endometriosis involving the uterosacral ligaments, rectovaginal septum, vaginal wall, pouch of Douglas, and rectosigmoid.¹⁷

Obstetric indications

Advanced imaging is considered medically necessary for diagnosis and management of ANY of the following:

Fetal anomalies
Assessment prior to fetal intervention
Placental complications
Complications related to monochorionic twins
Pelvimetry
Other obstetrical complications

IMAGING STUDY

Ultrasound is required for initial evaluation of fetal and placental conditions
Fetal MRI for indications involving the fetus or placenta, following nondiagnostic ultrasound
MRI pelvis for pelvimetry or other obstetrical complications

Uterine leiomyomata (fibroids)

Advanced imaging is considered medically necessary following nondiagnostic ultrasound in EITHER of the following scenarios:

When ultrasound features suggest leiomyosarcoma
For management prior to a fertility-sparing procedure, with the exception of MR-guided focused ultrasound

IMAGING STUDY

MRI pelvis

Gastrointestinal Indications

Appendicitis

Advanced imaging is considered medically necessary in EITHER of the following scenarios:

Diagnosis of suspected appendicitis
Perioperative management

IMAGING STUDY

Nonpregnant adults
- CT abdomen and pelvis
Pregnant women
- Ultrasound required for initial evaluation
- MRI abdomen and pelvis when ultrasound is nondiagnostic
- CT abdomen and pelvis when ultrasound is nondiagnostic and MRI is contraindicated or unavailable
Pediatric patients
- Ultrasound recommended for initial evaluation
- CT abdomen and/or pelvis when ultrasound cannot be performed or is nondiagnostic
- MRI abdomen and/or pelvis when ultrasound cannot be performed or is nondiagnostic

Rationale

The incidence of acute appendicitis is estimated at 3.4 million cases per year in the U.S. Typical signs and symptoms, including right lower quadrant pain, fever, anorexia, nausea, and vomiting, should lead to surgical consultation. When the diagnosis cannot be made on clinical exam alone, imaging modalities including ultrasound, CT, and MRI may be indicated. Alternative modalities may be considered in pediatric patients and pregnant women due to long-term concerns related to ionizing radiation.¹⁸

A meta-analysis of 29 studies evaluating the relative accuracies of ultrasound, CT, and MRI for clinically suspected acute appendicitis in children indicated high diagnostic accuracy for all 3 modalities and no statistically significant difference between them.¹⁹

A systematic review and meta-analysis found that, with an experienced sonographer, point of care ultrasound is appropriate as the initial imaging test in the evaluation of suspected acute appendicitis in patients of any age.²⁰

In a prospective cohort study of patients age 4 to 30 years to determine predictors for nondiagnostic ultrasound in clinically suspected acute appendicitis, body mass index greater than 85th percentile (odds ratio 4.9 [95% CI, 2.0-12.2]) and older age (odds ratio 1.1 [95% CI, 1.02-1.20]) were found to be statistically significant predictors of nondiagnostic ultrasound. Thus, in younger patients and those not classified as overweight, ultrasound is an appropriate initial study, while other modalities should be considered in older and overweight patients.²¹ In pediatric patients with a nondiagnostic ultrasound and clinically suspected appendicitis, MRI was found to have a sensitivity of 90% and specificity of 97.1%, while CT had a sensitivity of 88% and specificity of 98.6%, indicating comparable diagnostic utility of CT and MRI as secondary imaging modalities following ultrasound.²²

The American College of Radiology indicates that ultrasound is the preferred initial imaging modality in pediatric patients due to lack of ionizing radiation and an accuracy approaching that of CT. In pregnant women, ultrasound is also preferred for initial imaging evaluation, with MRI used as a secondary test when ultrasound is nondiagnostic.²³

Bowel obstruction

Advanced imaging is considered medically necessary for diagnosis and management.

IMAGING STUDY

Radiographs required for initial evaluation in pediatric patients
CT abdomen and/or pelvis when additional imaging is needed to guide treatment
MRI abdomen and/or pelvis in pediatric patients; MRI abdomen and/or pelvis in adults when CT cannot be performed or is nondiagnostic

Rationale

Abdominal radiography has moderate accuracy (approximately 83%) for the diagnosis of small bowel obstruction and is a useful initial test, especially in radiation-sensitive patients.²⁴ CT abdomen and pelvis is a more accurate exam that is less reader-dependent and can provide incremental information over radiographs in differentiating grade, severity, and etiology of small bowel obstructions that may lead to changes in management.²⁵ In children and younger patients with known or suspected small bowel obstructions or repetitive episodes of obstruction, MRI is indicated as the first-line imaging modality.^{26, 27}

Constipation (Pediatric only)

Also see Pelvic floor disorders indication (for adult and pediatric patients) in Miscellaneous Conditions

Advanced imaging is considered medically necessary for evaluation of symptoms persisting 2 or more weeks following nondiagnostic radiographs when ANY of the following are present:

Failure of medical management
Failure to thrive
Fever
Vomiting
Following barium enema or anal manometry when there is suspicion for ANY of the following:
- Anal stenosis
- Impaction in patients younger than 1 year of age
- Tight empty rectum

IMAGING STUDY

CT abdomen and/or pelvis
MRI abdomen and/or pelvis

Rationale

Constipation is a common problem in children and largely a clinical diagnosis. While a commonly performed practice, there is conflicting evidence that abdominal radiography substantially aids the diagnosis of constipation with at best small likelihood ratios (1-1.2) based on well designed studies.²⁸ Constipation can have both functional and organic causes. When constipation is associated with red flag features such as failure to thrive, unexplained weight loss, or vomiting, referral to a pediatric gastroenterologist should be considered and additional testing with colonoscopy and/or advanced imaging may be appropriate.^{29, 30}

Diverticulitis

Advanced imaging is considered medically necessary for diagnosis and management.

IMAGING STUDY

CT abdomen and/or pelvis

Rationale

CT abdomen and pelvis with intravenous contrast should be used to assess for diverticulitis based on recommendations from multiple high quality clinical guidelines. There is a lack of clinical data to support the use of MRI as a first-line modality in the diagnosis of diverticulitis.³¹

Enteritis or colitis, not otherwise specified

Includes ischemic, infectious colitis, neutropenic colitis, Henoch-Schonlein purpura, and radiation enteritis, and excludes inflammatory bowel disease.

Advanced imaging is considered medically necessary for diagnosis and management.

IMAGING STUDY

CT abdomen and/or pelvis

Rationale

CT with intravenous and oral contrast is indicated for suspected colonic ischemia to assess the distribution and phase of colitis. The diagnosis of colon ischemia can be suggested based on CT findings, such as bowel wall thickening, edema, or thumbprinting.³²

Gastrointestinal bleeding

Also see Vascular Imaging guidelines.

Advanced imaging is considered medically necessary for suspected small bowel source(s) of gastrointestinal bleeding following nondiagnostic endoscopy and colonoscopy.

IMAGING STUDY

CT abdomen and/or pelvis
MRI abdomen and/or pelvis when CT cannot be performed or is nondiagnostic

Inflammatory bowel disease (including Crohn’s disease and ulcerative colitis)

Advanced imaging is considered medically necessary in EITHER of the following scenarios:

Diagnosis of suspected Crohn’s disease following nondiagnostic colonoscopy in ANY of the following clinical scenarios when a patient:
- Meets criteria for irritable bowel syndrome with a normal colonoscopy and an elevated fecal calprotectin OR C-reactive protein (CRP) level
- Has concurrent upper gastrointestinal signs or symptoms with a nondiagnostic upper endoscopy
- Does not meet criteria for irritable bowel syndrome and does not have concurrent upper gastrointestinal signs or symptoms
Management of new or worsening symptoms to confirm exacerbation or evaluate for complications, including stricture, abscess, toxic megacolon, or fistula

IMAGING STUDY

CT abdomen and/or pelvis
MRI abdomen and/or pelvis

Rationale

MRI, CT, and ultrasound may be indicated as an adjunct to endoscopy for diagnosis of colonic inflammatory bowel disease (IBD), which remains the gold standard for diagnosis. MRI and CT have higher sensitivity for examining locations difficult to access by ultrasound.¹¹

Small bowel follow through and enteroclysis have high accuracy for mucosal abnormality and are widely available. They are less able to detect extramural complications and are contraindicated in high-grade obstruction and perforation. Radiation exposure is a major limitation. Ultrasound, CT, and MRI have high and comparable diagnostic accuracy at the initial presentation of terminal ileal Crohn’s disease. Small bowel follow through and enteroclysis have acceptable accuracy for mucosal disease, but are less accurate for mural disease and extramural complications.¹¹

Leukocyte scintigraphy also has the advantage of full gastrointestinal visualization and can detect sites of IBD within the small and large bowel.^10, ¹¹ Relative to CT/MRI, leukocyte scintigraphy has lower spatial resolution, higher radiation doses, and is less widely available, hence it is typically reserved as an add-on test when CT or MR entergraphy is nondiagnostic.

Calprotectin is a protein released by activated neutrophils, and elevated fecal levels are associated with inflammatory or malignant disease within the colon.³³ Serum C-reactive protein (CRP) is a marker of systemic inflammation. Fecal calprotectin is a sensitive marker for colonic inflammation and is recommended as an option to distinguish between IBD and irritable bowel syndrome (IBS).³⁴ A recent meta-analysis of 4 (CRP) and 8 (fecal calprotectin) studies found that a CRP level of ≤0.5 or calprotectin level of ≤40 μg/g confers a ≤1% probability of having IBD.³⁵

Upper endoscopy is usually not needed to establish the diagnosis of IBD in the majority of patients, but may be helpful when colonoscopy is nondiagnostic, especially in cases of IBD unspecified or when symptomatic.³⁶

Perianal fistula/abscess (fistula in ano)

Advanced imaging is considered medically necessary for diagnosis and management when incompletely characterized by physical exam.

IMAGING STUDY

CT pelvis
MRI pelvis (preferred)

Rationale

Because the management of perianal fistula is generally surgical, anatomic delineation is important in the management of this condition. Multiple high-quality evidence-based guidelines recommend the use of MRI.^25, ^37, ³⁸ Examination under anesthesia (EUA) also plays an important role, and anorectal ultrasound may be a useful initial imaging study where available. CT can identify perianal abscess, but is ionizing and has lower soft tissue contrast and diagnostic accuracy when compared to the preferred advanced imaging study, MRI.^25, ³⁸

Hepatobiliary Indications

Biliary tract dilatation or obstruction

Advanced imaging is considered medically necessary for diagnosis and management in EITHER of the following scenarios:

Unexplained biliary tract dilation
Biochemical evidence of biliary obstruction following nondiagnostic ultrasound

IMAGING STUDY

MRI/MRCP abdomen

Rationale

Dilation of the biliary tract includes a variety of etiologies ranging from benign (such as prior cholecystectomy, choledocholithiasis, inflammatory stricture) to malignant (such as cholangiocarcinoma). Ultrasound offers a non-ionizing, noninvasive view of the intra- and extrahepatic ducts, making it a good initial imaging exam. While ultrasound may be completely diagnostic, MRI/MRCP is a helpful add-on test for biliary duct dilation unexplained by ultrasound, to completely evaluate the biliary ducts when ultrasound is technically insufficient, and in select patients with high pretest likelihood of disease when ultrasound is normal.^39, ^40, ^{41, 42}

Cholecystitis

Advanced imaging is considered medically necessary for diagnosis and management in EITHER of the following scenarios:

Acute cholecystitis following nondiagnostic ultrasound
Complications of acute cholecystitis or cholecystectomy including perforation, abscess, gangrenous or hemorrhagic cholecystitis, gallstone ileus, Mirizzi’s syndrome, and bile leak

IMAGING STUDY

CT abdomen for complications of acute cholecystitis
MRI abdomen for complications of acute cholecystitis in pediatric patients; MRI abdomen in adults when CT cannot be performed or is nondiagnostic

Note: Advanced imaging not recommended for evaluation of acute uncomplicated cholecystitis.

Rationale

Cholecystitis is a common cause of right upper quadrant pain. Ultrasound has a high diagnostic accuracy for acute cholecystitis and is non-ionizing, widely available, quickly performed and noninvasive, making it an ideal first-line imaging test in suspected cases, an approach endorsed by multiple evidence-based and clinical practice guidelines.^5, ^{6, 43} Diagnostic testing strategies for suspected acute cholecystitis that start with CT (“initial CT”) are also more likely to lead to downstream overutilization, with a recent study finding that initial CT cohorts were 11 times more likely to undergo a second examination than initial ultrasound cohorts.⁴⁴

While ultrasound is usually sufficient for the diagnosis and management of acute uncomplicated cholecystitis, CT has comparable diagnostic accuracy for complicated cholecystitis and can accurately visualize gallbladder distention and wall thickening and identify complications of acute cholecystitis such as gallbladder wall emphysema, abscess formation, and perforation.⁴⁵

Hepatobiliary scintigraphy is a functional study that may be indicated when a bile leak is suspected post cholecystectomy or as an add-on test following nondiagnostic ultrasound.⁵ In a recent large (57 studies and 5859 patients) systematic review on the comparative diagnostic accuracy of imaging for acute cholecystitis, hepatobiliary scintigraphy was found to have higher sensitivity (96%; 95% CI, 94%-97%) than ultrasound (81%; 95% CI, 75%-87%) and similar specificity, equating to higher positive and similar negative likelihood ratios and greater overall diagnostic accuracy.⁴⁶ However, hepatobiliary scintigraphy is ionizing, less widely available, and takes longer to perform, hence best used as an add-on test following nondiagnostic ultrasound.

Choledocholithiasis

Advanced imaging is considered medically necessary for diagnosis and management following nondiagnostic ultrasound.

IMAGING STUDY

MRI/MRCP abdomen

Rationale

Choledocholithiasis is a common cause of biliary obstruction. Ultrasound has high diagnostic accuracy for acute cholecystitis and is non-ionizing, widely available, quickly performed and noninvasive, making it an ideal first line imaging test in suspected cases, an approach endorsed by multiple evidence-based and clinical practice guidelines.^41, ^42, ⁴⁵

When ultrasound is nondiagnostic, further diagnostic testing with either MRCP or endoscopic ultrasound (EUS) is recommended by multiple high quality evidence-based guidelines, especially in patients with intermediate pretest probability^41, ^42, ⁴⁵ Endoscopic ultrasound (EUS) is the gold standard, but MRCP has comparable diagnostic accuracy and is noninvasive. For intermediate pretest probability for choledocholithiasis (10%-50%), the summary sensitivity of EUS is 0.95 compared with 0.93 for MRCP, while summary specificity is 0.97 for EUS compared with 0.96 for MRCP.^{40, 42} Diagnostic ERCP has largely been replaced by EUS or MRCP, as the risk of post-ERCP pancreatitis is greater in a patient with normal caliber bile duct and normal bilirubin (odds ratio 3.4 for post-ERCP pancreatitis).⁴⁷

Diffuse liver disease

For hepatocellular cancer screening in high-risk patients, see the Oncologic Imaging guidelines.

Includes chronic hepatitis, cirrhosis, glycogen storage diseases, hemochromatosis, and Wilson’s disease.

Advanced imaging is considered medically necessary in ANY of the following scenarios:

Evaluation of suspected liver disease based on clinical findings or abnormal liver function tests when ultrasound is nondiagnostic and further evaluation is required
Evaluation for iron overload in hemochromatosis when chelation therapy or phlebotomy is being considered
Diagnosis and management of advanced hepatic fibrosis/cirrhosis in patients with established chronic liver disease in EITHER of the following scenarios:
- Nonalcoholic fatty liver disease (NAFLD) in patients with high risk for cirrhosis due to advanced age, obesity, diabetes, or alanine aminotransferase (ALT) level more than twice the upper limit of normal
- In other established chronic liver diseases when ultrasound elastography cannot be performed or is nondiagnostic

IMAGING STUDY

CT abdomen for EITHER of the following:
- Suspected liver disease
- Iron overload in hemochromatosis when MRI cannot be performed or is nondiagnostic
MRI abdomen for evaluation of hemochromatosis
MR elastography for diagnosis and management of advanced hepatic fibrosis/cirrhosis
Multiparametric MRI (LiverMultiScan) in EITHER of the following scenarios:
- As an alternative to MR elastography for diagnosis and management of advanced hepatic fibrosis/cirrhosis
- As an alternative to MRI abdomen for evaluation of hemochromatosis

Rationale

There are many potential causes of diffuse liver damage, including autoimmune disease, infection, hereditary conditions, and toxic or metabolic factors. A common presentation is asymptomatic transaminase elevation detected on routine laboratory testing. Advanced liver disease may manifest as jaundice or aberrations in the synthetic function of the liver.

When imaging is required, ultrasound is the initial study of choice for evaluation of both the liver parenchyma and biliary tree. In a study comparing ultrasonography of alcoholic liver disease to histological correlation, ultrasound had a sensitivity of 95% and specificity of 94%.⁴⁸Another study comparing histologic findings with ultrasonography for assessment of diffuse parenchymal disease found a sensitivity and specificity of 89% and 93%, respectively.⁴⁹

Limited data is available comparing accuracy of available cross-sectional imaging modalities. A small trial comparing the ability of ultrasound, CT, and MRI to determine diffuse liver steatosis demonstrated that opposed-phase MRI had the highest correlation with histopathology, compared to T2-weighted MRI with and without fat saturation, CT, and ultrasound for quantification of diffuse liver fat.⁵⁰ In a multicenter collaborative study evaluating the accuracy, sensitivity, and specificity of these imaging modalities for detecting liver cirrhosis, CT and MRI were not statistically better than ultrasound in receiver operating characteristic analysis.⁵¹

Hepatosplenic scintigraphy, typically performed with sulfur colloid, can be used to assess the function of the reticuloendothelial system and may be appropriate when results will determine whether a liver biopsy is performed or whether a potentially hepatotoxic medication is continued.⁵²

ELASTOGRAPHY

Liver biopsy is the gold standard for the diagnosis and staging of hepatic fibrosis. However, biopsy has limitations including the potential for sampling error as well as the potential for complications that accompanies any invasive procedure. Biopsy is alsoof limited utility in screening as well as evaluating for response to treatment. Several noninvasive techniques are being explored, including biochemical markers as well as imaging studies. Among the imaging studies being investigated are specific forms of ultrasound-based elastography, magnetic resonance elastography, and MRI with diffusion weighting. Elastography is a method of measuring the stiffness of a given tissue and may be done using ultrasound or magnetic resonance imaging, and may be used to diagnose and stage hepatic fibrosis in patients with chronic liver disease. Elastography is appropriate in patients with non-alcoholic fatty liver disease (NAFLD), alcoholic liver disease, hepatitis B, or hepatitis C. High quality evidence based guidelines from the American Gastroenterological Association Institute recommend MR elastography over vibration-controlled transient elastography to evaluate for cirrhosis in high-risk patients with NAFLD ⁵³ and guidelines from the American College of Radiology characterize MR elastography as generally appropriate for diagnosis of hepatic fibrosis.⁵⁴ Multiple recent systematic reviews have shown high diagnostic accuracy for MR elastography comparable⁵⁵ to marginally greater⁵⁶ than ultrasound based elastography depending on technique. One advantage of MR over ultrasound elastography is that the diagnostic accuracy of MR elastography is not compromised by obesity.^57, ^58, ⁵⁹ In addition, the diagnostic accuracy of MR elastography is similar regardless of the underlying etiology of chronic liver disease.

LiverMultiScan

LiverMultiScan (LMS) is a multiparametric MRI protocol consisting of proton density fat fraction (PDFF), T1, and T2* mapping sequences. A 2018 prospective validation study of 161 patients who had liver biopsies, transient elastography, Enhanced Liver Fibrosis (ELF) test, and contemporaneous LMS found sensitivity of 83% and negative predictive value of 96% for LMS, when evaluating for iron accumulation. In addition, though transient elastography was superior for identification and stratification of liver fibrosis, all three tests were comparable in detecting the presence of clinically significant (moderate or severe) liver fibrosis.⁶⁰ A 2020 prospective study of 145 patients compared quantitative mpMRI, vibration-controlled transient elastography (VCTE), magnetic resonance elastography (MRE), and 2D Shear-Wave elastography (SWE). For nonalcoholic fatty liver disease and nonalcoholic steatohepatitis (NASH), the MR liver fat measurement and controlled-attenuation parameter (CAP) included in LMS had good discriminatory performance while the elastography studies were not as effective.⁶¹

Focal liver lesion

For patients with a known primary malignancy, see the Oncologic imaging guidelines.

Advanced imaging is considered medically necessary in EITHER of the following scenarios:

Indeterminate lesions (not biopsied and not fully characterized by prior imaging)
- Initial evaluation of an indeterminate lesion identified on prior imaging when ANY of the following high-risk features are present:
  - Size larger than 1 cm in diameter
  - Known malignancy
  - Known cirrhosis
  - Hepatitis B or C
  - Alcoholism
  - Sclerosing cholangitis
  - Primary biliary cirrhosis
  - Choledochal cysts
  - Genetic or hereditary disease that predisposes to cirrhosis, including hemochromatosis
  - Anabolic steroid use
- Follow up or surveillance at 3 to 6 months when any of the above risk factors are present, or when the lesion is enhancing, poorly defined, or increasing in size
Benign lesions (biopsy-proven or fully characterized by imaging)
- Evaluation of symptoms suggesting a change in size or character
- Periodic surveillance of known hepatic adenoma

IMAGING STUDY

CT abdomen
MRI abdomen

Note: A simple liver cyst with benign characteristics on ultrasound may not require advanced imaging or surveillance. When multiple lesions are present, the largest and/or most suspicious lesion should be used to determine the appropriateness of advanced imaging and follow up.

Rationale

Common benign liver lesions, such as cysts and hemangiomas, usually have a characteristic appearance on ultrasound; this often eliminates the need for additional evaluation.⁶² In the setting of classic imaging findings and low risk for hepatic malignancy, ultrasonography is often sufficient.⁶² Otherwise, further evaluation with MRI should be considered.^{63, 64}

Cavernous hemangiomas are common; autopsy studies have shown that they occur in up to 7% of the population.^{65, 66} Hemangiomas appear as a homogenous hyperechoic mass, usually smaller than 3 cm in diameter with acoustic enhancement and sharp margins and are important to identify because they are benign lesions with a characteristic imaging appearance. Confident diagnosis of hemangioma can therefore avoid further biopsy and intervention. Triphasic CT and MRI are usually sufficient to establish the diagnosis.⁴² Hemangiomas usually show radiotracer uptake on RBC scintigraphy with high positive likelihood ratios and good interobserver agreement.^{67, 68} However, this is a historical technique that offers less information about alternative diagnoses and is typically reserved in situations where ultrasound is nondiagnostic and neither triphasic MRI nor CT can be performed. Similarly, sulfur colloid scintigraphy has been used to further characterize suspected focal nodular hyperplasia⁶⁹, but is rarely performed as both MRI and CT are usually diagnostic.

Simple cysts are also very common in the liver, occurring in about 5% of individuals. Cysts typically show through transmission with no internal echoes and a sharp distant border with edge shadowing on liver ultrasound.⁶⁵ Ultrasound is also usually sufficient to characterize small hepatic hemangiomas with typical characteristics in average risk individuals.⁷⁰

Small hepatic lesions (less than 1 cm) are difficult to characterize and biopsy, but have a high probability of being benign (higher than 80% even in patients with known malignancy),^{62, 71} thus close clinical follow up and monitoring for progression may be the most appropriate next step.⁷² In an otherwise healthy patient, an incidentally discovered focal liver lesion has an estimated probability of greater than 95% of being benign.⁷³

Liver lesions are commonly encountered and are commonly identified as incidental findings (incidentalomas) when imaging is performed for other indications. Evidence guiding appropriate use of advanced imaging for diagnosis and surveillance of incidental liver lesions is very limited. Carelon follows the primarily consensus-based approach of the American College of Radiology (ACR) incidental findings committee for hepatic lesions. The committee recommends full characterization of indeterminate lesions measuring more than 1 cm in diameter and in high-risk individuals, including those with a known primary malignancy with a propensity to metastasize to the liver, cirrhosis, chronic hepatitis, sclerosing cholangitis, hemochromatosis, alcoholism, and genetic or hereditary dispositions to cirrhosis.⁷²

In terms of appropriate follow up, the American Association for the Study of Liver Diseases, as part of the The American Board of Internal Medicine initiative, recommends that clinicians not perform CT or MRI routinely to monitor benign focal liver lesions unless there is a major change in clinical findings or symptoms.⁷¹ Benign hepatic neoplasms are usually managed conservatively—with the exception of hepatic adenomas due to their risk of rupture, especially when larger than 5 cm. Surveillance of hepatic adenomas in surgical candidates may therefore be appropriate with consensus-based intervals suggested by the European Association for the Study of the Liver (EASL).⁷⁰

Hepatomegaly

Advanced imaging is considered medically necessary for the diagnosis of clinically suspected or worsening hepatic enlargement when ultrasound is nondiagnostic.

IMAGING STUDY

CT abdomen
MRI abdomen in pediatric patients; MRI abdomen in adults when CT cannot be performed or is nondiagnostic

Jaundice

ADULT

Advanced imaging is considered medically necessary for the diagnosis of jaundice when unexplained by liver and biliary function tests.

PEDIATRIC

Advanced imaging is considered medically necessary following nondiagnostic ultrasound, for the diagnosis of jaundice when unexplained by liver and biliary function tests.

IMAGING STUDY

CT abdomen
MRI/MRCP abdomen

Rationale

Right upper quadrant ultrasound is the preferred first-line modality in patients with jaundice to evaluate for common bile duct dilation, presence of stones, and to direct any additional testing. If patient has jaundice with a suspected mechanical cause, right upper quadrant pain, or a history of stones, MRI abdomen with and without intravenous contrast and MRCP is second line.³⁹

Primary sclerosing cholangitis

Advanced imaging is considered medically necessary for diagnosis and management.

IMAGING STUDY

MRI/MRCP abdomen

Osseous Indications

Avascular necrosis, bilateral hip

Advanced imaging is considered medically necessary in EITHER of the following scenarios:

Diagnosis following negative or inconclusive radiographs
Preoperative planning for osteonecrosis with femoral head collapse

IMAGING STUDY

MRI pelvis
CT pelvis when MRI or bone scan not available or contraindicated

Rationale

Avascular necrosis or osteonecrosis is a form of ischemic bone necrosis due to vascular insufficiency. In 60%-75% of cases, avascular necrosis is associated with sickle cell disease, steroid use, alcoholism, chemoradiation, or metabolic bone disease.⁷⁴ Accurate grading is important for treatment as more advanced stages tend to require surgical intervention whereas medical treatments are favored in earlier stages. When initial radiographs demonstrate avascular necrosis and additional information is needed to guide treatment, MRI without IV contrast is usually appropriate.⁷⁵ Consensus among high-quality evidence-based guidelines also suggests that additional MRI imaging for avascular necrosis is also indicated in high-risk patients when radiographs are normal or inconclusive. Bone scan or CT may be substituted when MRI is not available.⁷⁴

Few studies have directly compared the accuracy of MRI and CT in the diagnosis of avascular necrosis, and most of these studies focus on the hip. Those findings are likely applicable to other joints as the disease process is similar. While consensus favors MRI, and MRI has the added benefit of not using ionizing radiation, CT may be more sensitive in detecting subchondral fractures than MRI (MRI had a relative sensitivity of 38% compared to CT for subchondral fracture detection).⁷⁶

Bone scintigraphy can also identify avascular necrosis that is occult on radiography but is usually recommended when MRI cannot be performed or is nondiagnostic.^74, ⁷⁷

Axial spondyloarthropathy

Advanced imaging is considered medically necessary in ANY of the following scenarios:

Diagnosis of nonradiographic spondyloarthropathy (nrSpA) when BOTH of the following are present:
- Radiographs which are negative or equivocal for sacroiliitis (Grade 0-2)
- Inflammatory back pain which has been present for at least 3 months. Inflammatory back pain is defined as back pain with at least FOUR (4) of the following features:
  - Patient is younger than age 40
  - Insidious (gradual) onset
  - Improvement with exercise
  - No improvement with rest
  - Pain at night that improves on getting up
Baseline imaging prior to therapy when the diagnosis is based on radiographic findings
Reevaluation in patients who have received at least 3 months of tumor necrosis factor inhibitors without clinical improvement

IMAGING STUDY

MRI pelvis

Rationale

Axial spondyloarthritis includes a group of rare (estimated 0.25% to 1% prevalence) disorders that may be HLA-B27 positive and that manifest with inflammatory changes around the enthesis. Spondyloarthritis includes ankylosing spondylitis, reactive arthritis, psoriatic arthritis, arthropathy associated with inflammatory bowel disease, and undifferentiated spondyloarthritis.

The Assessment of SpondyloArthritis International Society (ASAS) has developed and validated criteria for spondyloarthritis, as well as for their subsets: axial spondyloarthritis and peripheral spondyloarthritis.⁷⁸ While sacroiliitis is the most common MRI manifestation of axial spondyloarthropathy, bone marrow edema can be seen in the vertebrae as well and characteristic patterns have been described.⁷⁹

There is consensus among guidelines that radiography of the pelvis and/or spine is the preferred imaging modality for initial evaluation of spondyloarthritis. Radiographs of the whole spine are recommended as the first-line imaging modality.⁸⁰ Plain film X-ray of the sacroiliac joints should be considered for suspected axial spondyloarthritis, unless the person is likely to have an immature skeleton.⁸¹ In patients with ankylosing spondylitis (not nonradiographic axial spondyloarthritis), initial conventional radiography of the lumbar and cervical spine is recommended to detect syndesmophytes, which are predictive of development of new syndesmophytes.⁸²

The ASAS criteria for axial spondyloarthritis have a high diagnostic accuracy, sensitivity 82% and specificity 88% based on a systematic review of 9 papers and 5739 patients.⁷⁸ Patients that do not meet the ASAS criteria are a low pretest probability group unlikely to have axial spondyloarthropathy. The ASAS criteria for axial spondyloarthritis include age < 45 years, back pain of at least 3 months duration, sacroiliitis on imaging (either definitive changes on radiography or evidence from MRI) and one characteristic feature, and HLA-B27 positive; or at least 2 characteristic clinical features, which include arthritis, uveitis, dactylitis, psoriasis, Crohn’s disease, positive nonsteroidal anti-inflammatory drug response, family history, and positive HLA-B27.

Diagnostic criteria for ASAS are based on MRI of the sacroiliac joints, not the spine. MRI of the spine has a low yield in patients with a negative sacroiliac joint MRI and should not be routinely performed. A retrospective study of 1191 patients under age 45 with chronic lower back pain found sacroiliitis in approximately 7% of patients. Less than 2% of patients with a negative sacroiliac joint MRI had a positive spine MRI, and spine MRI changed management in only 0.16% of cases.⁸³ MRI can demonstrate edema of the vertebral body corners (also known as corner inflammatory lesions) and bone marrow edema. A positive MRI spine is defined as 3 or more lesions present on 2 or more slices, but this definition is used primarily for research purposes.⁸³

Consensus among guidelines is that MRI should be obtained in patients with persistent clinical suspicion when radiography is negative or indeterminate. When a diagnosis of axial spondyloarthritis cannot be confirmed and clinical suspicion remains high, a follow up MRI should be considered.⁸² When radiographs are negative and there is suspicion of spondyloarthritis, MRI is mandatory to look for early inflammatory lesions.⁸⁰ Plain film X-rays, ultrasound, and/or MRI should be considered for other peripheral and axial symptomatic sites.⁸¹

A negative/indeterminate radiograph d oes not satisfy the New York Criteria for Ankylosing Spondylitis (bilateral grade 2–4 or unilateral grade 3–4 sacroiliitis [evidence of erosions, sclerosis, joint space widening, narrowing or ankyloses]) and does not otherwise explain the back pain.

MRI of the sacroiliac joints and/or spine may be used to assess and monitor disease activity in axial spondyloarthritis, providing additional information on top of clinical and biochemical assessments. The decision on when to repeat MRI depends on the clinical circumstances. In general, short tau inversion recovery sequences are sufficient to detect inflammation and the use of contrast medium is not needed.⁸²

Developmental hip dysplasia (Pediatric only)

Advanced imaging is considered medically necessary for preoperative planning.

IMAGING STUDY

CT pelvis

Osseous tumor

Advanced imaging is considered medically necessary for diagnosis and management.

IMAGING STUDY

CT pelvis
MRI pelvis for pediatric patients; MRI pelvis in adults when CT cannot be performed or is nondiagnostic

Note: MRI or radionuclide bone scintigraphy (bone scan) may be more appropriate for detection of skeletal metastases and primary bone tumors.

Osteoid osteoma

Advanced imaging is considered medically necessary following negative or inconclusive hip radiographs.

IMAGING STUDY

CT pelvis

Osteomyelitis

Advanced imaging is considered medically necessary for diagnosis and management.

IMAGING STUDY

MRI pelvis
CT pelvis when MRI or bone scan not available or contraindicated

Rationale

Though radiographs often do not show abnormalities associated with osteomyelitis in the first 2 weeks of the infection, they can detect other pathology that may contribute to the patient’s symptoms. The information provided by radiographs generally complements that provided by other modalities, so radiographs should be performed even when other imaging is planned.

Radiographs are the appropriate initial imaging study in osteomyelitis because they can demonstrate findings suggestive of the diagnosis, but can also exclude or provide information to suggest other diagnoses. The sensitivity of radiography is reportedly 43%-75% and the specificity is 75%-83%. Abnormal radiographs are helpful, but diagnosis cannot be excluded solely on the basis of negative radiographs. Although sensitivity and specificity of CT are not well established, sensitivity of CT is known to be lower than sensitivity of MRI. For this reason, the utility of CT is limited to specific situations. For example, CT can be used to detect bony sequestra, and has an important role in determining operative therapy.⁸⁴

Overall, CT has a limited role in the diagnosis of osteomyelitis, and should be used only when imaging is being done to assess the extent of bone destruction, to direct a biopsy, or when MRI is contraindicated. For early detection of osteomyelitis, MRI is superior to other imaging modalities. The sensitivity and specificity for MRI are 78%-90% and 60%-90%, respectively. This compares to sensitivity and specificity of 67% and 50% for CT, and 14%-54% and 68%-70% for radiography.⁸⁵

The American College of Radiology Appropriateness Criteria indicates that for initial imaging evaluation of suspected osteomyelitis, radiographs are rated as “usually appropriate.” CT, MRI, and ultrasound are all rated as “usually not appropriate,” regardless of whether the studies are to be performed with intravenous contrast. For evaluation of suspected osteomyelitis following radiographs, MRI without and with intravenous contrast is preferred, although radiographs and MRI are both indicated and complementary. MRI without contrast is generally appropriate if contrast is contraindicated, and CT with intravenous contrast is generally appropriate if MRI is contraindicated.

Functional imaging with bone scintigraphy has historically been used to evaluate for osteomyelitis when radiographs are nondiagnostic. Greater accuracy and the lack of ionizing radiation for MRI have largely made scintigraphy an add-on test when MRI cannot be performed or is nondiagnostic^74, ^85, ⁸⁶ although bone scintigraphy offers a wider field of view and hence can localize multifocal disease. Similarly, leukocyte scintigraphy is usually not appropriate in the initial evaluation of osteomyelitis,⁸⁶ but may play a complementary role to bone scintigraphy in specific scenarios such as multifocal disease.

Pelvic fracture

Includes sacral insufficiency fracture, stress fracture, and traumatic fracture.

Advanced imaging is considered medically necessary in EITHER of the following scenarios:

Diagnosis or management of sacral insufficiency fracture
Diagnosis or management of stress fracture or traumatic fracture following nondiagnostic pelvic or sacral radiographs

IMAGING STUDY

Radiographs required prior to advanced imaging for fracture indications other than sacral insufficiency fracture
CT or MRI pelvis following inconclusive radiographs or initial evaluation of sacral insufficiency fracture

Sacroiliitis, not otherwise specified

Advanced imaging is considered medically necessary for diagnosis and management following pelvic or sacral radiographs in EITHER of the following scenarios:

Condition predisposing to sacroiliitis, such as inflammatory bowel disease, psoriasis, or infection, when radiographs are negative or equivocal for sacroiliitis
Radiographs equivocal for sacroiliitis

IMAGING STUDY

CT pelvis
MRI pelvis

Rationale

Sacroiliitis is an inflammatory process involving the sacroiliac joints, and is generally seen in the setting of seronegative spondyloarthropathies. There is consensus among guidelines that radiography is the initial imaging modality of choice in evaluation of the sacroiliac joints. When there is clinical suspicion for sacroiliitis and radiographs are negative or equivocal, MRI of the pelvis is appropriate to evaluate for mild or early inflammatory changes.^80-82

Septic arthritis

Advanced imaging is considered medically necessary for diagnosis and management.

IMAGING STUDY

MRI pelvis
CT pelvis when MRI or bone scan not available or contraindicated

Pancreatic Indications

Pancreatic duct dilatation

Advanced imaging is considered medically necessary for evaluation of pancreatic duct dilatation seen on ultrasound or CT.

IMAGING STUDY

MRI/MRCP abdomen

Pancreatic mass, indeterminate solid

Advanced imaging is considered medically necessary for diagnosis, management, and surveillance.

IMAGING STUDY

CT abdomen or CT abdomen and pelvis, with pancreatic protocol
MRI abdomen

Pancreatic mass, indeterminate cystic (IPMN/IPMT)

Note: Common differential considerations for an indeterminate cystic pancreatic mass include intraductal papillary mucinous neoplasm/tumor (IPMN/IPMT), serous/mucinous cystadenoma (SCA/MCA), and pseudocyst.

Note: Indications apply only to asymptomatic cystic pancreatic masses. For symptomatic masses, see relevant symptom-based indication. Unless otherwise specified, enlarging cysts often require endoscopic ultrasound (EUS)/fine needle aspiration (FNA).

ADULT

Advanced imaging is considered medically necessary for diagnosis, management, and surveillance in surgical candidates when EUS/FNA has not been performed or is nondiagnostic in ANY of the following scenarios:

Initial evaluation of an indeterminate mass identified on ultrasound
Age 80 or greater at the time of diagnosis: every other year for up to 4 years or every other year if enlarging
Cysts less than 1.5 cm
- Age less than 65 at diagnosis: every 12 months for up to 9 years from the time of initial diagnosis
- Age 65 to 79 at diagnosis: every 24 months for up to 10 years from the time of initial diagnosis, or every 12 months if the lesion has worrisome features (enhancing nodules or peripheral calcification) or if the patient has high risk of pancreatic malignancy
Cysts 1.5 cm or greater
- Every 6-12 months for 2 years then yearly for up to 10 years

PEDIATRIC

Advanced imaging is considered medically necessary for diagnosis, management, and surveillance.

IMAGING STUDY

CT abdomen or CT abdomen and pelvis
MRI/MRCP abdomen

Rationale

Cystic pancreatic lesions are commonly encountered incidental findings (incidentalomas). Evidence guiding appropriate use of advanced imaging for diagnosis, management, and surveillance of incidental liver lesions is very limited, However, a primarily consensus-based approach suggested by the American College of Radiology (ACR) incidental findings committee for pancreatic cysts is commonly used in practice.⁸⁷ The common differential for an incidentally discovered cystic pancreatic mass in adults includes intraductal papillary mucinous neoplasm (IPMN), serous cystadenoma (SCA), mucinous cystic neoplasm, and pseudocyst. These lesions have variable malignant potential and are difficult to differentiate, especially when small, making surveillance a common alternative to more invasive management. Frequency of surveillance depends on age, cyst size, interval growth, and the presence of high-risk imaging features such as enhancing nodules, peripheral calcification, or dilation of the main pancreatic duct. Either multiphasic contrast enhanced CT or MRI can be used in the diagnosis, management, and surveillance of cystic pancreatic lesions. While availability and local practice experience impact the modality decision, MRI is non-ionizing and offers greater softer tissue contrast. MRCP may also be helpful in the initial characterization of the cystic pancreatic lesion to define relationship to the main pancreatic duct.⁸⁷ While uncommon, pediatric cystic pancreatic masses are outside the scope of the ACR incidental findings committee recommendations and evidence guiding diagnosis, management, and/or surveillance is very limited.

Pancreatitis

Advanced imaging is considered medically necessary in EITHER of the following scenarios:

Evaluation of suspected complications due to acute pancreatitis (see pancreatic pseudocyst)
Recurrent acute pancreatitis of uncertain etiology, defined as more than 2 attacks of acute pancreatitis without established end-stage chronic pancreatitis

Note: Patients with mild acute or uncomplicated pancreatitis usually do not require cross-sectional imaging, aside from ultrasound for identification of gallstones and/or biliary ductal calculi.

IMAGING STUDY

CT abdomen or CT abdomen and pelvis
MRI abdomen in pediatric patients; MRI abdomen in adults when CT cannot be performed
MRCP for recurrent acute pancreatitis to evaluate suspected pancreatic duct anomalies

Rationale

Biochemical testing is more sensitive than CT and often sufficient to make the diagnosis of acute uncomplicated pancreatitis in both children and adults.^{88, 89} Therefore, CT is not indicated and should not be ordered routinely for patients with mild acute pancreatitis.⁹⁰

CT should be performed selectively when a broad differential diagnosis that includes acute pancreatitis must be narrowed, especially when biochemical testing is negative or in patients with acute pancreatitis and a suspected local complication (e.g., peritonitis, signs of shock, suggestive ultrasound findings).⁴⁰ Triphasic CT is accurate for the detection of complications in acute pancreatitis including pseudocysts, pancreatic necrosis, portal vein thrombosis, and visceral artery pseudoaneurysms. MRI or MRCP may be indicated when a biliary cause for pancreatitis is suspected, especially for recurrent attacks.⁹¹

Renal, Adrenal, and Urinary Tract Indications

Adrenal mass, indeterminate

For patients with a known primary malignancy, see the Oncologic imaging guidelines.

ADULT

Advanced imaging is considered medically necessary in EITHER of the following scenarios:

Diagnosis and management of an indeterminate adrenal mass in ANY of the following scenarios:
- Greater than 2 cm
- New or growing within the past 12 months (when prior imaging is available)
- Biochemical evidence of an adrenal mass
- Initial evaluation of an indeterminate mass identified on ultrasound
Surveillance
- 1 – 2 cm: Single 12-month follow up
- Greater than 2 cm unless ANY of the following benign imaging features are present:
  - Absolute wash out greater than 60% or relative wash out greater than 40%
  - Lesion attenuation less than 10 Hounsfield units (HU)
  - Stable over a 12-month interval and less than 4 cm

PEDIATRIC

Advanced imaging is considered medically necessary for diagnosis, management, and surveillance EITHER of the following scenarios:

In neonates, when ultrasound cannot be performed or is nondiagnostic
In non neonates

IMAGING STUDY

CT abdomen
MRI abdomen

Rationale

Incidental adrenal masses, or adrenal incidentalomas, are frequently encountered and represent a diagnostic challenge. Evidence for appropriate surveillance intervals is limited. However, a primarily consensus based approach suggested by the American College of Radiology (ACR) incidental findings committee for adrenal masses is commonly used in practice.⁹² For indeterminate lesions 2 cm or less without prior imaging or known primary malignacy, 12-month surveillance is suggested. For indeterminate lesions that are enlarging, greater than 2 cm, or present in patients with a known malignancy, further characterization with contrast enhanced CT or MRI or resection is recommended depending on lesion size.

Markers suggestive of malignancy include size greater than 4 cm, irregular margins, nonhomogeneous content, nonuniform enhancement, surrounding tissue invasion or metastasis, attenuation coefficient of 10 Hounsfield units (HU) or greater on noncontrast CT scan, low washout rate on delayed view of contrast CT, and growth over a year.^92, ⁹³ No follow up is recommended for lesions with benign features ^{94, 95}, specifically lesions with an attenuation of less than 10 HU on non contrast CT. A recent systematic review of 3 studies and 153 patients found the CT less than 10 HU criterion to be 100% sensitive (95% CI, 91%-100%) and 72% specific (95% CI, 60%-82%).⁹⁴ Among more than 2300 patients included in published follow-up studies, there is no report of adrenal malignancy in adrenal incidentalomas displaying typical features of adrenocortical adenomas on initial imaging studies.⁹⁴

Pediatric adrenal masses are outside the scope of the ACR incidental findings committee recommendations and evidence guiding diagnosis, management, and/or surveillance is very limited. Ultrasound is used in the initial evaluation of neonatal adrenal masses because it is non-ionizing and does not require sedation.

Bladder or urethral diverticula

Advanced imaging is considered medically necessary for diagnosis and management.

IMAGING STUDY

MRI pelvis

Hematuria

ADULT

Advanced imaging is considered medically necessary for diagnosis and management in ANY of the following scenarios:

Traumatic hematuria
Macroscopic hematuria
Microscopic hematuria in EITHER of the following scenarios:
- Symptomatic
- Asymptomatic in EITHER of the following scenarios:
  - High-risk patients (defined as ANY of the following):
    - Age greater than 59 years
    - More than 30 pack year smoking history
    - More than 25 red blood cells per high powered field (RBC/HPF)
    - History of gross hematuria
  - Low or intermediate risk patients (those not meeting the high risk criteria above) when ALL of the following criteria are met:
    - Persistent and unexplained following repeat urinalysis
    - Negative renal ultrasound
    - Nondiagnostic cystoscopy

PEDIATRIC

Advanced imaging is considered medically necessary for diagnosis and management in EITHER of the following scenarios:

Traumatic hematuria
Atraumatic hematuria when ultrasound is nondiagnostic

IMAGING STUDY

CT abdomen and/or pelvis
MRI abdomen and pelvis (MR urogram) in pediatric patients; MRI abdomen and pelvis (MR urogram) in adults when CT cannot be performed or is nondiagnostic

Rationale

In patients presenting with macroscopic hematuria, the incidence of urological malignancy is 0%-9.3% depending on patient population, with higher rates in male smokers over age 60 and lower rates in patients less than 35.⁹⁶ Advanced imaging is helpful to exclude malignancy in select scenarios and changes management in up 53% of patients.⁹⁷

Incidence of malignancy is lower in patients presenting with asymptomatic atraumatic microscopic hematuria, typically defined as fewer than 3 red blood cells per high powered field (RBC/HPF) on urinalysis. However, once benign causes have been ruled out based on history, physical and laboratory evaluation, the presence of asymptomatic microhematuria should prompt a urologic evaluation which may include advanced imaging. ⁹⁸ Examples of benign causes include vigorous exercise, UTI, recent menstruation, known medical renal disease, and recent urological procedures. Advanced imaging is helpful to further characterize macroscopic hematuria. A recent update to a high quality evidence based guideline by the American Urological Association (AUA) recommends that all high risk patients with asymptomatic microhematuria undergo prompt evaluation with CT urography and cystoscopy (strong recommendation based on low quality evidence). Low or intermediate risk patients have a significantly lower pre test likelihood for upper tract malignancy and should first undergo repeat urinalysis and/or cystoscopy and renal ultrasound (moderate (for low risk) and strong (for intermediate risk) recommendation based on low quality evidence). CT urography could be considered in these lower risk patients on a case by case basis if microhematuria remains persistent and unexplained.⁹⁹

Advanced imaging is helpful to further characterize macroscopic hematuria. Incidence of malignancy is much lower in pediatric patients with hematuria and ultrasound is usually recommended as an initial imaging test because it is non-ionizing and has good diagnostic accuracy for renal stones.¹⁰⁰

When advanced imaging is indicated, multiphasic CT urography (without and with intravenous contrast), including sufficient phases to evaluate the renal parenchyma to rule out a renal mass and an excretory phase to evaluate the urothelium of the upper tracts, is the modality of choice because it has the highest sensitivity and specificity for imaging the upper tracts.⁹⁸ MR urography is an option that may be considered as an add on test when contrast enhanced CT is contraindicated.⁹⁹

Hydronephrosis

Advanced imaging is considered medically necessary for diagnosis and management following nondiagnostic pelvic ultrasound.

IMAGING STUDY

CT abdomen and/or pelvis
MRI abdomen and pelvis (MR urogram) in pediatric patients; MRI abdomen and pelvis (MR urogram) in adult patients when CT cannot be performed or is nondiagnostic

Rationale

Ultrasound, CT, and MRI are all able to detect the presence or absence of hydronephrosis. Ultrasound has moderate diagnostic accuracy, is widely available, and is nonionizing, making it a good initial imaging study when hydronephrosis is suspected.¹⁰¹ CT and MRI are able to visualize the full course of the ureter and are useful when ultrasound is nondiagnostic. CT is more established, quicker, less motion sensitive, and more commonly performed than MRI ¹⁰², although MRI may be useful in pediatric or radiation-sensitive populations. Renal scintigraphy is a functional study that can help differentiate obstructive from nonobstructive hydronephrosis and so determine the clinical significance of suspected hydronephosis, including the impact on renal function and the presence or absence of obstructive uropathy.^{8, 9, 103, 104}

Nephrocalcinosis

Advanced imaging is considered medically necessary for diagnosis and management following nondiagnostic ultrasound.

IMAGING STUDY

CT abdomen

Polycystic kidney disease

Advanced imaging is considered medically necessary for diagnosis and management following nondiagnostic ultrasound, to evaluate total kidney volume AND to assist in decisions on medical therapy.

IMAGING STUDY

CT abdomen or CT abdomen/pelvis
MRI abdomen

Pyelonephritis

Advanced imaging is considered medically necessary in ANY of the following scenarios:

Acute pyelonephritis in persons with diabetes, history of renal calculi or renal surgery
Lack of clinical improvement following 72 hours of antibiotic therapy to evaluate for complications such as abscess or another surgical condition
Diagnosis or management of xanthogranulomatous pyelonephritis

IMAGING STUDY

CT abdomen
MRI abdomen when CT cannot be performed or is nondiagnostic

Renal artery stenosis/Renovascular hypertension

See Vascular Imaging guidelines.

Renal masses (includes renal cysts)

For patients with a known primary malignancy, or for renal cancer screening in patients with a genetic predisposition, see the Oncologic imaging guidelines.

See separate indication for Polycystic kidney disease.

ADULT

Advanced imaging is considered medically necessary in patients with a known renal mass and a genetic or medical predisposition to renal cancer or in ANY of the following scenarios:

Diagnosis and management of an indeterminate renal mass in ANY of the following scenarios:
- Initial evaluation of an indeterminate mass identified on ultrasound
- Growth (more than 3 mm per year) over a 5-year period
- Mass with at least one suspicious feature (ANY of the following):
  - Thick or irregular cyst wall
  - Mural nodule
  - Calcification
  - Greater than 20 HU on a contrast enhanced CT or between 21 and 69 HU on a noncontrast CT
  - Infiltrative or ill defined
Management of a solid benign renal mass with new or worsening symptoms
Surveillance
- Bosniak IIF: 6 months and 12 months after initial diagnosis, then annually until 5 years from the time of initial diagnosis
- Solid renal mass suspicious for renal cancer or Bosniak III or IV complex cyst: initial at 6-12 months after initial diagnosis, then annually when part of an active surveillance management strategy

Note: Classification is based on the Bosniak criteria prior to the 2019 update.

PEDIATRIC

Advanced imaging is considered medically necessary for diagnosis, management, and surveillance of an indeterminate renal mass or for management of a solid benign renal mass with active surveillance or with new or worsening symptoms.

Note: Surveillance assumes a dedicated renal protocol CT or MRI has previously been performed for the lesion in question. Renal lesions with benign features do not require further diagnostic imaging.

IMAGING STUDY

CT abdomen
MRI abdomen

Note: Simple cysts with benign characteristics on ultrasound do not require advanced imaging or surveillance.

Rationale

When evaluating an incidental renal lesion, previous imaging results should be obtained if available to assess lesion stability. Simple cysts and non calcified renal masses containing macroscopic fat (suggesting angiomyolipomas) are usually fully characterized with ultrasound and/or a noncontrast CT. Benign masses established by imaging or biopsy may require advanced imaging if symptomatic (for instance, due to rupture of microaneurysms within an AML) or as part of active surveillance when growth of the mass will determine whether it is resected.

For an indeterminate cystic renal mass, the Bosniak classification based on results from a CT or MRI with and without contrast is a well-validated tool for management, although evidence for appropriate surveillance intervals is limited. A primarily consensus-based approach has been suggested by the American College of Radiology (ACR) incidental findings committee for adult renal masses and is commonly used in practice.¹⁰⁵ Renal cysts classified Bosniak category I or II require no follow up and include simple cysts, cysts with thin septa and hemorrhagic cysts. Bosniak subcategory IIF cysts are minimally complex and include cysts with nodular calcifications, multiple thickened or thin enhancing septa or hyperdense cysts greater than 3 cm. IIF cysts have a real but low probability of malignancy and may be followed with CT or MRI at 6 months, 12 months, and then yearly for 5 years in patients without limited life expectancy. Cysts categorized Bosniak III or IV are usually treated surgically, but may be followed as part of active surveillance at 6 to 12 months, then yearly for 5 years, especially in patients who are poor surgical candidates or who have limited life expectancy.¹⁰⁵ ¹⁰⁶

The Bosniak classification requires a CT or MRI with and without contrast to determine the presence or absence of enhancement within the mass. Masses that are indeterminate on ultrasound or that have suspicious features on non-contrast CT should undergo a with and without contrast exam for Bosniak characterization.

Pediatric renal masses vary widely in the malignant potential¹⁰⁷ and are outside the scope of the ACR incidental findings committee as are patients with established malignancy or a genetic predisposition.

Urinary tract calculi

ADULT

Advanced imaging is considered medically necessary in ANY of the following scenarios:

Initial evaluation of suspected calculus in patients with no history of nephrolithiasis
Suspected recurrence* when ANY of the following apply:
- History of radiolucent calculus
- History of radiopaque calculus and atypical presentation
- History of recent radiopaque calculus and typical presentation in EITHER of the following scenarios:
  - In patients less than age 50, following nondiagnostic ultrasound
  - In patients 50 years of age or greater
Management and follow up of known calculi when ANY of the following apply:
- Planned percutaneous nephrolithotomy, ureteroscopy, or shock wave lithotripsy, when CT has not been performed within the preceding 30 days
- Symptomatic patients with known radiolucent calculi
- Symptomatic patients with radiopaque calculi, following nondiagnostic KUB or ultrasound
- Asymptomatic patients with persistent hydronephrosis on ultrasound following shock wave lithotripsy or ureteroscopic stone extraction
Pregnancy
- Diagnosis or management following nondiagnostic ultrasound or KUB

*Recurrence applies when the patient has a prior history of stones but the prior episode has resolved (either the stone is known to have passed based on clinical follow-up, or prior imaging has shown resolution).

PEDIATRIC

Advanced imaging is considered medically necessary following nondiagnostic ultrasound or kidney, ureter, and bladder radiograph.

IMAGING STUDY

Radiograph or ultrasound required in pregnant women and pediatric patients
CT abdomen and/or pelvis

Rationale

INITIAL EVALUATION

CT is preferred by the majority of the evidence based guidelines although initial ultrasound evaluation is also appropriate. Ultrasound has been shown to have lower sensitivity but comparable specificity to CT in detecting ureteral stones. It is safe, reproducible, and inexpensive, and can detect upper urinary tract dilatation.^108-110 CT detects important incidental findings in patients over 80 years of age in 28.9% of cases.¹¹¹ CT should be avoided for patients presenting to the emergency department with symptoms consistent with uncomplicated renal colic who are younger than 50 years of age, otherwise healthy, and with known histories of kidney stones or ureterolithiasis.¹¹²

MANAGEMENT

In a randomized controlled trial, 2500 nonobese adult patients with suspected nephrolithiasis (without a solitary kidney or dialysis dependence) presenting in the emergency department were randomized to initial ultrasound vs CT. No difference was found between the 2 groups in the rates of clinically significant alternative diagnoses, hospitalizations, return emergency department visits, or diagnostic accuracy.¹¹³ Use of CT prior to percutaneous nephrolithotomy (PCNL) is a strong recommendation based on low quality evidence from the American Urological Association (AUA).¹¹⁴ The AUA also makes a conditional recommendation based on low quality evidence for the use of CT to optimize patient selection for shock wave lithotripsy (SWL) instead of ureteroscopy (American Urological Association, 2016, #57) and both approaches are supported by the European Association of Urology (EAU) in their recommendation to “consider the stone composition before deciding on the method of removal”.¹¹⁵ Post-procedure, the presence of residual known radiopaque calculi in symptomatic patients can often be initially evaluated with radiography and/or ultrasound as suggested by AUA algorithms.¹¹⁵

As ultrasound has moderate-to-high diagnostic accuracy for nephrolithiasis and is non-ionizing, it is the initial modality of choice in radiation-sensitive populations including in pediatrics and pregnancy.¹¹⁵

Splenic Indications

Splenic mass, benign

Advanced imaging is considered medically necessary for management following nondiagnostic ultrasound or rapid growth.

IMAGING STUDY

CT abdomen
MRI abdomen

Splenic mass, indeterminate

For patients with a known primary malignancy, see the Oncologic imaging guidelines.

Advanced imaging is considered medically necessary in ANY of the following scenarios:

Initial evaluation of an indeterminate mass identified on ultrasound
Enlarging over time
Features suspicious for malignancy (ANY of the following):
- Heterogenous enhancement
- Irregular margins
- Necrosis
- Multiple lesions
- Extension beyond the margin of the spleen
Surveillance: every 6 months for up to 1 year

IMAGING STUDY

CT abdomen
MRI abdomen

Rationale

Guidelines from the American College of Radiology incidental findings committee on splenic and nodal findings recommend further evaluation with advanced imaging or biopsy when splenic masses with suspicious features are identified in patients with a known malignancy or in patients without a known primary but with suspicious features. For patients with an incidentally discovered splenic mass without a known primary and indeterminate features, follow up imaging at 6 and 12 months is recommended. Indeterminate splenic masses that have been stable for at least a year do not typically require imaging follow up.¹¹⁶

Splenomegaly

Advanced imaging is considered medically necessary for clinically suspected or worsening splenic enlargement following nondiagnostic ultrasound.

IMAGING STUDY

CT abdomen
MRI abdomen in pediatric patients; MRI abdomen in adults when CT cannot be performed or is nondiagnostic

Miscellaneous Conditions

Hemoperitoneum

Advanced imaging is considered medically necessary for diagnosis and management.

IMAGING STUDY

CT abdomen and/or pelvis

Hernia

Includes femoral, internal, inguinal, Spigelian, ventral, and incisional hernia.

Advanced imaging is considered medically necessary in EITHER of the following scenarios:

Suspected complications
Presurgical planning

IMAGING STUDY

Ultrasound required for initial evaluation in pediatric patients
CT abdomen and/or pelvis
MRI abdomen and/or pelvis for pediatric patients; MRI abdomen and/or pelvis in adults when CT cannot be performed or is nondiagnostic

Rationale

CT detects occult hernias in approximately 11% of cases and assists in the differential diagnosis of hernia vs other abdominal wall mass. It is useful in surgical planning to define the abdominal wall anatomy in nonmidline hernias such as those on the flanks, suprapubic or subxiphoid regions, and to identify posterior abdominal wall defects.¹¹⁷

MRI is favored for groin hernias when ultrasound is nondiagnostic. Sensitivity and specificity for MRI are 94.5% and 96.3%, respectively, vs 83% and 67%-83%, respectively, for CT.¹¹⁸

Lymphadenopathy

For patients with a known primary malignancy, see the Oncologic imaging guidelines.

Advanced imaging is considered medically necessary in ANY of the following scenarios:

Diagnosis
- In patients with clinical or laboratory findings suggestive of a lymphoproliferative disorder
Management of lymphadenopathy with suspicious features* when EITHER of the following apply:
- Enlarging over time
- Clinical or laboratory findings suggestive of a lymphoproliferative disorder
Surveillance of lymphadenopathy with suspicious features:
- 3 months and 12 months after initial diagnosis

IMAGING STUDY

CT abdomen and/or pelvis
MRI abdomen and/or pelvis when CT cannot be performed or is nondiagnostic

Note: MRI may be useful to differentiate enlarged lymph nodes from vascular structures following unenhanced CT scan.

*Note: Suspicious features are defined as ANY of the following:

Greater than 1 cm in short axis diameter
Necrosis
Hypervascularity
Abnormal morphology including loss of the fatty hilum and thickened cortex
Cluster of lymph nodes

Rationale

Lymphadenopathy can be due to reactive, infectious, inflammatory or lymphoproliferative etiologies. Guidelines from the American College of Radiology incidental findings committee on splenic and nodal findings recommend further evaluation with advanced imaging or biopsy when lymph nodes with suspicious features are identified in patients with a history of malignancy or when lymphoproliferative disorder is suspected. When clinical evaluation suggests a benign cause for lymphadenopathy, 3-month follow-up CT or MRI is recommended and no follow up is recommended if the nodes have been stable over a 12-month duration.¹¹⁶

Pelvic floor disorders

Advanced imaging is considered medically necessary for diagnosis and management in EITHER of the following scenarios:

Functional disorder of the pelvic floor associated with urinary or bowel incontinence
Chronic constipation, when anorectal manometry or balloon expulsion tests are nondiagnostic

IMAGING STUDY

MRI pelvis
Dynamic MRI (MR defecography) may be of benefit in some clinical scenarios^{119, 120}

Retroperitoneal conditions

Advanced imaging is considered medically necessary for diagnosis and management of ANY of the following retroperitoneal conditions:

Fibrosis
Inflammation
Bleeding
Mass

IMAGING STUDY

CT abdomen and/or pelvis
MRI abdomen and/or pelvis for pediatric patients; MRI abdomen and/or pelvis in adults when CT cannot be performed or is nondiagnostic

Sports hernia (athletic pubalgia)

Advanced imaging is considered medically necessary when ALL the following criteria are met:

Pain is insidious, progressive, and worsens with Valsalva or movement
No detectable inguinal or ventral hernia on exam
Pain has persisted for least 6 weeks
Radiographs are nondiagnostic
Symptoms have not improved following at least 6 weeks of conservative therapy
Patient is a surgical candidate

IMAGING STUDY

MRI pelvis

Rationale

Athletic pubalgia is a term used to describe chronic groin pain which is of insidious onset and occurs with exertion. Though its incidence in female patients is increasing, the diagnosis predominantly occurs in males. It is uncertain whether this is due to differences in the intensity of exercise in the affected patients, or differences in the anatomy which may reduce the susceptibility of female patients to this condition.¹²¹

Conventional radiographs are generally the initial imaging modality in the evaluation of groin pain. Radiographs can identify or exclude conditions such as tumor, fracture, osteoarthritis, or advanced avascular necrosis, that may account for the patient’s symptoms. Though no single modality has demonstrated adequate sensitivity and specificity for making the diagnosis, specific findings associated with the diagnosis have been described on both MRI and dynamic ultrasonography.¹²²

Initial treatment is nonsurgical and may include anti-inflammatory medication, rest, heat or ice, and deep massage. Physical therapy may also be helpful. Surgical management should be considered in patients who do not respond to a 6- to 8-week course of nonsurgical management and after other causes for the pain have been excluded via history and physical examination as well as imaging studies.¹²³

Perioperative evaluation, not otherwise specified

Transplant-related imaging

Advanced imaging is considered medically necessary in the following scenarios:

For living donors, a single pre-transplant evaluation
For patients on the transplant waiting list for liver transplantation, annual surveillance
Evaluation of suspected post-transplant complications

Note: For patients on the transplant list but who have not undergone transplantation and who have a change in clinical condition, please refer to the applicable sign- or symptom-based indication.

IMAGING STUDY

CT abdomen or CT abdomen/pelvis
MRI abdomen as an alternative to CT abdomen for surveillance in patients on the waiting list for liver transplantation

Nonspecific Signs and Symptoms

Abdominal and/or pelvic pain, undifferentiated

Note: Nonacute abdominal pain is defined as pain that has occurred at least 1 day per week for at least 90 days. Abdominal pain should be evaluated in the context of a differential diagnosis based on findings from history, physical exam, and relevant lab results. Usually, the appropriateness of imaging for abdominal pain should be evaluated based on the most likely diagnosis. This guideline applies to patients with atraumatic abdominal pain without a clear source when a most likely diagnosis cannot be established or is uncertain (undifferentiated).

ADULT

Advanced imaging is considered medically necessary in EITHER of the following scenarios:

Acute abdominal pain associated with clinical findings of a surgical abdomen, including severe undifferentiated abdominal pain or guarding or that remains unexplained after ALL of the following:
- History
- Physical exam
- Lab results where relevant
- Prior imaging where available
- Ultrasound if the pain localizes to the right upper quadrant (abdominal ultrasound) or female pelvis (pelvic ultrasound)
Nonacute abdominal pain that remains unexplained after ALL of the following:
- History
- Physical exam
- Lab results where relevant
- Prior imaging where available
- Ultrasound if the pain is localized to the right upper quadrant (abdominal ultrasound) or female pelvis (pelvic ultrasound)
- Upper endoscopy if the pain is epigastric unless associated with elevated inflammatory markers (leukocytosis, C-reactive protein [CRP])
- Colonoscopy if the pain is associated with defecation and a change in the form and frequency of stools (i.e., irritable bowel syndrome)

PEDIATRIC

Advanced imaging is considered medically necessary for diagnosis in ANY of the following scenarios:

Acute abdominal pain associated with clinical findings of a surgical abdomen, including severe undifferentiated abdominal pain or guarding or that remains unexplained after ALL of the following:
- History
- Physical exam
- Lab results where relevant
- Prior imaging where available
- Abdominal or pelvic ultrasound
Chronic or recurrent pelvic pain following nondiagnostic ultrasound
Chronic or recurrent abdominal pain following nondiagnostic ultrasound when ANY of the following red flag signs are present:
- Chronic severe diarrhea (at least 3 watery stools per day for more than 2 weeks)
- Deceleration of linear growth
- Fever of unknown origin
- Gastrointestinal bleeding
- History of a genetic or congenital syndrome
- Immunocompromised
- Involuntary weight loss
- Persistent focal abdominal pain, especially right upper or right lower quadrant
- Persistent vomiting
- Elevated inflammatory markers (leukocytosis, C-reactive protein [CRP])

IMAGING STUDY

CT abdomen for upper quadrant (right or left) and epigastric pain
CT abdomen and/or pelvis for lower quadrant (right or left) and generalized abdominal pain
CT pelvis for pelvic pain
MRI pelvis for pelvic pain
MRI abdomen in pediatric patients; MRI abdomen in adults when CT cannot be performed

Rationale

ACUTE ABDOMINAL PAIN

In adult patients with unexplained, nonspecific atraumatic abdominal pain, CT has high diagnostic accuracy in the evaluation of acute abdominal pain and is recommended by multiple guidelines when the pain is unexplained by clinical and, where relevant, laboratory evaluation.¹²⁴ ¹²⁵ CT is the also the single best diagnostic adjunct to augment the clinical exam. While combinations of clinical and laboratory findings offer modest positive (3.2) and negative (.69) likelihood ratios for the diagnosis of acute abdominal pain, the addition of CT improves these ratios to 9.2 and 0.09, effectively ruling in and out acute disease where positive and negative.¹²⁶ Two exceptions to the initial use of CT are for pain localizing to the right upper quadrant and female pelvis given the high diagnostic accuracy of ultrasound for hepatobiliary and uterine/adnexal disease.¹³

In pediatric patients with unexplained, nonspecific atraumatic abdominal pain, CT is not always necessary.¹²⁷ Ultrasound is suggested as an initial imaging modality¹²⁸, as it is non-ionizing and can establish the diagnosis for several causes of pain including appendicitis, cholecystitis, hernia, hemorrhagic cysts, and testicular or ovarian torsion. CT is useful when ultrasound is nondiagnostic or unavailable and in emergent situations where the use of ultrasound may delay the diagnosis (such as peritonitis).

CHRONIC ABDOMINAL PAIN

CT is often used in adults with chronic atraumatic abdominal pain, but the utility of CT and its position in the diagnostic testing strategy vary by location of the pain. Ultrasound is recommended in the initial evaluation of right upper quadrant pain, since the pain is often hepatobiliary in origin³⁹ (see also hepatobiliary indications). For right/left lower quadrant pain, ultrasound has lower diagnostic accuracy and is more operator dependent, thus CT is commonly recommended as a first line imaging test.^18, ^129, ¹³⁰ Patients with organic epigastric pain not better accounted for by pancreatitis, diverticulitis, hepatobiliary or other more specific indications are more likely to have a gastrointestinal than a hepatobiliary etiology for their symptoms¹³¹, typically dyspepsia and an ulcer. Endoscopy, not CT, is usually the initial imaging test in patients with dyspepsia who have failed empiric therapy or who have red flag features.¹³² Advanced imaging may be helpful in patients with significantly elevated WBC or ESR, as the positive predictive value for intra-abdominal pathology is high.¹³³ Advanced imaging is not typically needed in patients who meet the Rome 3 or 4 criteria for irritable bowel syndrome (IBS). While the pretest probability for structural disease in patients with IBS is comparable to the population average¹³⁴, additional investigations may be required in the presence of red flags, such as age over 50, unintended weight loss, or persistent diarrhea. Colonoscopy, not routine CT or MRI, is the imaging test of choice.¹³⁵

The American Academy of Pediatrics notes that functional abdominal pain generally can be diagnosed correctly without the need for additional diagnostic tests if the patient is 4 to 18 years of age with chronic abdominal pain when there are no alarm symptoms or signs, the physical examination is normal, and the stool sample tests are negative for occult blood.¹³⁶ However, the American Academy of Pediatrics also recommends further evaluation in a subgroup of patients with alarm or red flag features which include involuntary weight loss, deceleration of linear growth, gastrointestinal blood loss, significant vomiting, chronic severe diarrhea, persistent right upper or right lower quadrant pain, unexplained fever, family history of inflammatory bowel disease, or abnormal or unexplained physical findings. These features indicate a need to perform diagnostic testing for specific anatomic, infectious, inflammatory, or metabolic etiologies on the basis of specific symptoms.¹³⁶ Significant focal tenderness is also an alarm feature. Advanced imaging may be indicated in the presence of red flag features associated with chronic or recurrent pediatric abdominal pain.

Fever of unknown origin

Advanced imaging is considered medically necessary in EITHER of the following scenarios:

Fever of duration greater than 3 weeks which is unexplained following a standard diagnostic evaluation to identify the source
Unexplained fever in immunocompromised patient

IMAGING STUDY

CT abdomen and/or pelvis

Lower extremity edema

Advanced imaging is considered medically necessary for evaluation when diffuse and unexplained by venous ultrasound.

IMAGING STUDY

CT abdomen and/or pelvis
MRI abdomen and/or pelvis in pediatric patients; MRI abdomen and/or pelvis in adults when CT cannot be performed or is nondiagnostic

Rationale

Diffuse swelling of the lower extremities has a variety of causes, including lymphedema due to chronic lymphatic insufficiency.¹³⁷ Lymphoscintigraphy can help to determine whether obstruction to lymphatic flow is responsible for diffuse swelling and help to direct both medical and surgical interventions.^{137, 138}

Weight loss

Also see Chest Imaging guidelines.

Advanced imaging is considered medically necessary for evaluation of unintentional weight loss exceeding 5% of body weight within a 12-month interval in EITHER of the following scenarios:

Persistence following a negative comprehensive clinical evaluation (including a history and physical examination, age-appropriate cancer screening, chest radiography, and initial laboratory evaluation) after a period of observation
Abnormal findings suggestive of malignancy on history, physical exam, imaging, or laboratory evaluation

IMAGING STUDY

CT abdomen and/or pelvis

Rationale

Persistent unintentional weight loss is defined as a substantive weight loss over a period of 6 to 12 months.¹³⁹ Weight loss is not uncommon in elderly patients and is typically related to one of the 7 Ds: dementia, dentition, depression, diarrhea, drugs, functional dysfunction, or dysphagia. When unintentional weight loss remains unexplained, it may be due to the 8^th D: acute or chronic disease.¹³⁹

The primary purpose of advanced imaging in the evaluation of unexplained unintentional weight loss is to exclude an occult malignancy not detected by initial clinical evaluation and testing, usually in patients with abnormalities on baseline testing. CT screening is of limited value. Instead, diagnostic testing should be directed toward areas of concern based on the history and physical examination.¹⁴⁰ Age-appropriate screening for malignancy (mammogram, pap smear) should also be encouraged.¹⁴¹

The most common cause of malignancy among patients with unintentional weight loss is of gastrointestinal primary (47%), and gastrointestinal causes account for 45% of nonmalignant organic etiologies.¹⁴² Therefore, endoscopy and/or colonoscopy should be considered for initial evaluation when there is evidence for a gastrointestinal source.

CT with contrast is sensitive for the detection of lymphoma, lung, and genitourinary cancers, which are the next most common causes of malignancy in patients with unintentional weight loss.

References

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2. Spottswood SE, Pfluger T, Bartold SP, et al. SNMMI and EANM practice guideline for meckel diverticulum scintigraphy 2.0. J Nucl Med Technol. 2014;42(3):163-9.

3. Irvine I, Doherty A, Hayes R. Bleeding meckel’s diverticulum: A study of the accuracy of pertechnetate scintigraphy as a diagnostic tool. European Journal of Radiology. 2017;96:27-30.

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17. Nisenblat V, Bossuyt PM, Farquhar C, et al. Imaging modalities for the non-invasive diagnosis of endometriosis. Cochrane Database Syst Rev. 2016;2:Cd009591.

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19. Zhang H, Liao M, Chen J, et al. Ultrasound, computed tomography or magnetic resonance imaging – which is preferred for acute appendicitis in children? A Meta-analysis. Pediatr Radiol. 2017;47(2):186-96.

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23. Smith MP, Katz DS, Lalani T, et al. ACR Appropriateness Criteria right lower quadrant pain–suspected appendicitis. Ultrasound Q. 2015;31(2):85-91.

24. Thompson WM, Kilani RK, Smith BB, et al. Accuracy of abdominal radiography in acute small-bowel obstruction: does reviewer experience matter? AJR Am J Roentgenol. 2007;188(3):W233-8.

25. Maung AA, Johnson DC, Piper GL, et al. Evaluation and management of small-bowel obstruction: an Eastern Association for the Surgery of Trauma practice management guideline. J Trauma Acute Care Surg. 2012;73(5 Suppl 4):S362-9.

26. Mullan CP, Siewert B, Eisenberg RL. Small bowel obstruction. AJR Am J Roentgenol. 2012;198(2):W105-17.

27. Fidler J. MR imaging of the small bowel. Radiol Clin North Am. 2007;45(2):317-31.

28. Reuchlin-Vroklage LM, Bierma-Zeinstra S, Benninga MA, et al. Diagnostic value of abdominal radiography in constipated children: a systematic review. Arch Pediatr Adolesc Med. 2005;159(7):671-8.

29. El-Chammas K, Majeskie A, Simpson P, et al. Red flags in children with chronic abdominal pain and Crohn’s disease-a single center experience. J Pediatr. 2013;162(4):783-7.

30. Di Lorenzo C, Colletti RB, Lehmann HP, et al. Chronic abdominal pain in children: a technical report of the American Academy of Pediatrics and the North American Society for Pediatric Gastroenterology, Hepatology and Nutrition. J Pediatr Gastroenterol Nutr. 2005;40(3):249-61.

31. Sartelli M, Catena F, Ansaloni L, et al. WSES Guidelines for the management of acute left sided colonic diverticulitis in the emergency setting. World J Emerg Surg. 2016;11:37.

32. Brandt LJ, Feuerstadt P, Longstreth GF, et al. ACG clinical guideline: epidemiology, risk factors, patterns of presentation, diagnosis, and management of colon ischemia (CI). Am J Gastroenterol. 2015;110(1):18-44; quiz 5.

33. Erbayrak M, Turkay C, Eraslan E, et al. The role of fecal calprotectin in investigating inflammatory bowel diseases. Clinics (Sao Paulo). 2009;64(5):421-5.

34. National Institute for Health and Care Excellence, Faecal calprotectin diagnostic tests for inflammatory diseases of the bowel, (2013) London, National Institute for Health and Care Excellence, 56 pgs.

35. Menees SB, Powell C, Kurlander J, et al. A meta-analysis of the utility of C-reactive protein, erythrocyte sedimentation rate, fecal calprotectin, and fecal lactoferrin to exclude inflammatory bowel disease in adults with IBS. Am J Gastroenterol. 2015;110(3):444-54.

36. Danelius M, Ost A, Lapidus AB. Inflammatory bowel disease-related lesions in the duodenal and gastric mucosa. Scand J Gastroenterol. 2009;44(4):441-5.

37. Vogel JD, Johnson EK, Morris AM, et al. Clinical practice guideline for the management of anorectal abscess, fistula-in-ano, and rectovaginal fistula. Dis Colon Rectum. 2016;59(12):1117-33.

38. Ong EM, Ghazi LJ, Schwartz DA, et al. Guidelines for imaging of Crohn’s perianal fistulizing disease. Inflamm Bowel Dis. 2015;21(4):731-6.

39. Lalani T, Couto CA, Rosen MP, et al. ACR appropriateness criteria jaundice. J Am Coll Radiol. 2013;10(6):402-9.

40. Greenberg JA, Hsu J, Bawazeer M, et al. Clinical practice guideline: management of acute pancreatitis. Can J Surg. 2016;59(2):128-40.

41. National Institute for Health and Care Excellence, Gallstone disease: diagnosis and management of cholelithiasis, cholecystitis and choledocholithiasis, (2014) London, National Institute for Health and Care Excellence, 11 pgs.

42. Williams E, Beckingham I, El Sayed G, et al. Updated guideline on the management of common bile duct stones (CBDS). Gut. 2017;66(5):765-82.

43. University of Michigan Health System, Evaluation and management of gallstone-related diseases in non-pregnant adults, (2014) Ann Arbor, MI, University of Michigan Health System.

44. Ginsburg D, Paroder V, Flusberg M, et al. Diagnosis of acute cholecystitis: why do patients get multiple studies? Emergency Radiology. 2016;23(1):49-55.

45. European Association for the Study of the Liver (EASL). EASL Clinical Practice Guidelines on the prevention, diagnosis and treatment of gallstones. J Hepatol. 2016;65(1):146-81.

46. Kiewiet JJ, Leeuwenburgh MM, Bipat S, et al. A systematic review and meta-analysis of diagnostic performance of imaging in acute cholecystitis. Radiology. 2012;264(3):708-20.

47. Tenner S, Baillie J, DeWitt J, et al. American College of Gastroenterology guideline: management of acute pancreatitis. Am J Gastroenterol. 2013;108(9):1400-15; 16.

48. Taylor KJ, Gorelick FS, Rosenfield AT, et al. Ultrasonography of alcoholic liver disease with histological correlation. Radiology. 1981;141(1):157-61.

49. Joseph AE, Saverymuttu SH, al-Sam S, et al. Comparison of liver histology with ultrasonography in assessing diffuse parenchymal liver disease. Clin Radiol. 1991;43(1):26-31.

50. Qayyum A, Chen DM, Breiman RS, et al. Evaluation of diffuse liver steatosis by ultrasound, computed tomography, and magnetic resonance imaging: which modality is best? Clin Imaging. 2009;33(2):110-5.

51. Kudo M, Zheng RQ, Kim SR, et al. Diagnostic accuracy of imaging for liver cirrhosis compared to histologically proven liver cirrhosis. A multicenter collaborative study. Intervirology. 2008;51 Suppl 1:17-26.

52. Royal HD, Brown ML, Drum DE, et al. Procedure guideline for hepatic and splenic imaging. Society of Nuclear Medicine. J Nucl Med. 1998;39(6):1114-6.

53. Lim JK, Flamm SL, Singh S, et al. American Gastroenterological Association Institute guideline on the role of elastography in the evaluation of liver fibrosis. Gastroenterology. 2017;152(6):1536-43.

54. Horowitz JM, Kamel IR, Arif-Tiwari H, et al. ACR Appropriateness Criteria chronic liver disease. J Am Coll Radiol. 2017;14(11s):S391-s405.

55. Xiao G, Zhu S, Xiao X, et al. Comparison of laboratory tests, ultrasound, or magnetic resonance elastography to detect fibrosis in patients with nonalcoholic fatty liver disease: A meta-analysis. Hepatology. 2017;66(5):1486-501.

56. Guo Y, Parthasarathy S, Goyal P, et al. Magnetic resonance elastography and acoustic radiation force impulse for staging hepatic fibrosis: a meta-analysis. Abdom Imaging. 2015;40(4):818-34.

57. Singh S, Venkatesh SK, Loomba R, et al. Magnetic resonance elastography for staging liver fibrosis in non-alcoholic fatty liver disease: a diagnostic accuracy systematic review and individual participant data pooled analysis. Eur Radiol. 2016;26(5):1431-40.

58. Singh S, Venkatesh SK, Wang Z, et al. Diagnostic performance of magnetic resonance elastography in staging liver fibrosis: a systematic review and meta-analysis of individual participant data. Clin Gastroenterol Hepatol. 2015;13(3):440-51.e6.

59. Su LN, Guo SL, Li BX, et al. Diagnostic value of magnetic resonance elastography for detecting and staging of hepatic fibrosis: a meta-analysis. Clin Radiol. 2014;69(12):e545-52.

60. McDonald N, Eddowes PJ, Hodson J, et al. Multiparametric magnetic resonance imaging for quantitation of liver disease: a two-centre cross-sectional observational study. Sci Rep. 2018;8(1):9189.

61. Imajo K, Tetlow L, Dennis A, et al. Quantitative multiparametric magnetic resonance imaging can aid non-alcoholic steatohepatitis diagnosis in a Japanese cohort. World J Gastroenterol. 2021;27(7):609-23.

62. Marin D, Furlan A, Federle MP, et al. Imaging approach for evaluation of focal liver lesions. Clin Gastroenterol Hepatol. 2009;7(6):624-34.

63. Lamba R, Fananapazir G, Corwin MT, et al. Diagnostic imaging of hepatic lesions in adults. Surg Oncol Clin N Am. 2014;23(4):789-820.

64. Belghiti J, Cauchy F, Paradis V, et al. Diagnosis and management of solid benign liver lesions. Nat Rev Gastroenterol Hepatol. 2014;11(12):737-49.

65. Venkatesh SK, Chandan V, Roberts LR. Liver masses: a clinical, radiologic, and pathologic perspective. Clin Gastroenterol Hepatol. 2014;12(9):1414-29.

66. Garrett R. Solid liver masses: approach to management from the standpoint of a radiologist. Curr Gastroenterol Rep. 2013;15(12):359.

67. Farlow DC, Chapman PR, Gruenewald SM, et al. Investigation of focal hepatic lesions: is tomographic red blood cell imaging useful? World J Surg. 1990;14(4):463-7.

68. Bradley M, Stewart I, Metreweli C. Diagnosis of the peripheral cavernous haemangioma: comparison of ultrasound, CT and RBC scintigraphy. Clin Radiol. 1991;44(1):34-7.

69. Bhoil A, Gayana S, Sood A, et al. Hybrid single photon emission computed tomography/computed tomography sulphur colloid scintigraphy in focal nodular hyperplasia. World J Nucl Med. 2013;12(3):124-5.

70. European Association for the Study of the Liver (EASL). EASL Clinical Practice Guidelines on the management of benign liver tumours. J Hepatol. 2016;65(2):386-98.

71. American Association for the Study of Liver Diseases, Five things physicians and patients should question, (2014), Choosing Wisely.

72. Pang EH, Harris AC, Chang SD. Approach to the solitary liver lesion: imaging and when to biopsy. Can Assoc Radiol J. 2016;67(2):130-48.

73. Dietrich CF, Sharma M, Gibson RN, et al. Fortuitously discovered liver lesions. World J Gastroenterol. 2013;19(21):3173-88.

74. Bussieres AE, Taylor JA, Peterson C. Diagnostic imaging practice guidelines for musculoskeletal complaints in adults–an evidence-based approach. Part 1. Lower extremity disorders. J Manipulative Physiol Ther. 2007;30(9):684-717.

75. Tuite MJ, Kransdorf MJ, Beaman FD, et al. ACR Appropriateness Criteria acute trauma to the knee. J Am Coll Radiol. 2015;12(11):1164-72.

76. Stevens K, Tao C, Lee SU, et al. Subchondral fractures in osteonecrosis of the femoral head: comparison of radiography, CT, and MR imaging. AJR Am J Roentgenol. 2003;180(2):363-8.

77. Murphey MD, Roberts CC, Bencardino JT, et al. ACR Appropriateness Criteria osteonecrosis of the hip. J Am Coll Radiol. 2016;13(2):147-55.

78. Sepriano A, Rubio R, Ramiro S, et al. Performance of the ASAS classification criteria for axial and peripheral spondyloarthritis: a systematic literature review and meta-analysis. Ann Rheum Dis. 2017;76(5):886-90.

79. Baraliakos X, Braun J. Imaging scoring methods in axial spondyloarthritis. Rheum Dis Clin North Am. 2016;42(4):663-78.

80. Schueller-Weidekamm C, Mascarenhas VV, Sudol-Szopinska I, et al. Imaging and interpretation of axial spondylarthritis: the radiologist’s perspective–consensus of the Arthritis Subcommittee of the ESSR. Semin Musculoskelet Radiol. 2014;18(3):265-79.

81. National Institute for Health Care Excellence, Spondyloarthritis in over 16s: diagnosis and management, (2017) London, National Institute for Health and Care Excellence, 205 pgs.

82. Mandl P, Navarro-Compan V, Terslev L, et al. EULAR recommendations for the use of imaging in the diagnosis and management of spondyloarthritis in clinical practice. Ann Rheum Dis. 2015;74(7):1327-39.

83. Ez-Zaitouni Z, Bakker PA, van Lunteren M, et al. The yield of a positive MRI of the spine as imaging criterion in the ASAS classification criteria for axial spondyloarthritis: results from the SPACE and DESIR cohorts. Ann Rheum Dis. 2017;76(10):1731-6.

84. Pineda C, Vargas A, Rodriguez AV. Imaging of osteomyelitis: current concepts. Infect Dis Clin North Am. 2006;20(4):789-825.

85. Hatzenbuehler J, Pulling TJ. Diagnosis and management of osteomyelitis. Am Fam Physician. 2011;84(9):1027-33.

86. Beaman FD, von Herrmann PF, Kransdorf MJ, et al. ACR Appropriateness Criteria suspected osteomyelitis, septic arthritis, or soft tissue infection (excluding spine and diabetic foot). J Am Coll Radiol. 2017;14(5s):S326-s37.

87. Megibow AJ, Baker ME, Morgan DE, et al. Management of incidental pancreatic cysts: a white paper of the ACR Incidental Findings Committee. J Am Coll Radiol. 2017;14(7):911-23.

88. Coffey MJ, Nightingale S, Ooi CY. Diagnosing acute pancreatitis in children: what is the diagnostic yield and concordance for serum pancreatic enzymes and imaging within 96 h of presentation? Pancreatology. 2014;14(4):251-6.

89. Treacy J, Williams A, Bais R, et al. Evaluation of amylase and lipase in the diagnosis of acute pancreatitis. ANZ J Surg. 2001;71(10):577-82.

90. Quinlan JD. Acute pancreatitis. Am Fam Physician. 2014;90(9):632-9.

91. Surlin V, Saftoiu A, Dumitrescu D. Imaging tests for accurate diagnosis of acute biliary pancreatitis. World J Gastroenterol. 2014;20(44):16544-9.

92. Mayo-Smith WW, Song JH, Boland GL, et al. Management of incidental adrenal masses: a white paper of the ACR Incidental Findings Committee. J Am Coll Radiol. 2017;14(8):1038-44.

93. Song JH, Grand DJ, Beland MD, et al. Morphologic features of 211 adrenal masses at initial contrast-enhanced CT: can we differentiate benign from malignant lesions using imaging features alone? AJR Am J Roentgenol. 2013;201(6):1248-53.

94. Fassnacht M, Arlt W, Bancos I, et al. Management of adrenal incidentalomas: European Society of Endocrinology Clinical Practice Guideline in collaboration with the European Network for the Study of Adrenal Tumors. Eur J Endocrinol. 2016;175(2):G1-g34.

95. Lee JM, Kim MK, Ko SH, et al. Clinical guidelines for the management of adrenal incidentaloma. Endocrinol Metab (Seoul). 2017;32(2):200-18.

96. Lokken RP, Sadow CA, Silverman SG. Diagnostic yield of CT urography in the evaluation of young adults with hematuria. AJR Am J Roentgenol. 2012;198(3):609-15.

97. Pandharipande PV, Alabre CI, Coy DL, et al. Changes in physician decision making after CT: a prospective multicenter study in primary care settings. Radiology. 2016;281(3):835-46.

98. American College of Radiology, ACR Appropriateness Criteria(r) hematuria, (2014), American College of Radiology.

99. Barocas DA, Boorjian SA, Alvarez RD, et al. Microhematuria: AUA/SUFU guideline. J Urol. 2020;204(4):778-86.

100. Expert Panel on Pediatric Imaging, Dillman JR, Rigsby CK, et al. ACR Appropriateness Criteria hematuria-child. J Am Coll Radiol. 2018;15(5S):S91-S103.

101. Wong C, Teitge B, Ross M, et al. The accuracy and prognostic value of point-of-care ultrasound for nephrolithiasis in the emergency department: a systematic review and meta-analysis. Acad Emerg Med. 2018;25(6):684-98.

102. Fritzsche P, Amis ES, Jr., Bigongiari LR, et al. Acute onset flank pain, suspicion of stone disease. American College of Radiology. ACR Appropriateness Criteria. Radiology. 2000;215 Suppl:683-6.

103. Blaufox MD, De Palma D, Taylor A, et al. The SNMMI and EANM practice guideline for renal scintigraphy in adults. Eur J Nucl Med Mol Imaging. 2018;45(12):2218-28.

104. Taylor AT, Brandon DC, de Palma D, et al. SNMMI procedure standard/EANM practice guideline for diuretic renal scintigraphy in adults with suspected upper urinary tract obstruction 1.0. Semin Nucl Med. 2018;48(4):377-90.

105. Herts BR, Silverman SG, Hindman NM, et al. Management of the incidental renal mass on CT: a white paper of the ACR Incidental Findings Committee. J Am Coll Radiol. 2018;15(2):264-73.

106. Campbell S, Uzzo RG, Allaf ME, et al. Renal mass and localized renal cancer: AUA Guideline. J Urol. 2017;198(3):520-9.

107. Malkan AD, Loh A, Bahrami A, et al. An approach to renal masses in pediatrics. Pediatrics. 2015;135(1):142-58.

108. American Urological Association, Clinical effectiveness protocols for imaging in the management of ureteral calculous disease: AUA technology assessment, (2012), American Urological Association.

109. European Association of Urology, Guidelines on urolithiasis, (2017), European Association of Urology, 84 pgs.

110. Bredemeyer M. ACR Appropriateness Criteria for acute onset of flank pain with suspicion of stone disease. Am Fam Physician. 2016;94(7):575-6.

111. Samim M, Goss S, Luty S, et al. Incidental findings on CT for suspected renal colic in emergency department patients: prevalence and types in 5,383 consecutive examinations. J Am Coll Radiol. 2015;12(1):63-9.

112. Abrahamian FM, Krishnadasan A, Mower WR, et al. Association of pyuria and clinical characteristics with the presence of urinary tract infection among patients with acute nephrolithiasis. Annals of Emergency Medicine. 2013;62(5):526-33.

113. Smith-Bindman R, Aubin C, Bailitz J, et al. Ultrasonography versus computed tomography for suspected nephrolithiasis. N Engl J Med. 2014;371(12):1100-10.

114. American Urological Association, Surgical management of stones: American Urological Association/Endourological Society guideline, (2016), American Urological Association.

115. European Association of Urology, Guidelines on urolithiasis, (2015), European Association of Urology.

116. Heller MT, Harisinghani M, Neitlich JD, et al. Managing incidental findings on abdominal and pelvic CT and MRI, part 3: white paper of the ACR Incidental Findings Committee II on splenic and nodal findings. J Am Coll Radiol. 2013;10(11):833-9.

117. Earle D, Roth JS, Saber A, et al. SAGES guidelines for laparoscopic ventral hernia repair. Surg Endosc. 2016;30(8):3163-83.

118. Simons MP, Aufenacker T, Bay-Nielsen M, et al. European Hernia Society guidelines on the treatment of inguinal hernia in adult patients. Hernia. 2009;13(4):343-403.

119. Martin-Martin GP, Garcia-Armengol J, Roig-Vila JV, et al. Magnetic resonance defecography versus videodefecography in the study of obstructed defecation syndrome: Is videodefecography still the test of choice after 50 years? Tech Coloproctol. 2017;21(10):795-802.

120. Carter D, Saukhat O, Alcalay M, et al. Magnetic imaging defecography results are comparable to high-resolution manometry and conventional X-ray defecography in the assessment of functional pelvic floor disorders. Tech Coloproctol. 2020;24(11):1155-61.

121. Robinson P, Bhat V, English B. Imaging in the assessment and management of athletic pubalgia. Semin Musculoskelet Radiol. 2011;15(1):14-26.

122. Suarez JC, Ely EE, Mutnal AB, et al. Comprehensive approach to the evaluation of groin pain. J Am Acad Orthop Surg. 2013;21(9):558-70.

123. Farber AJ, Wilckens JH. Sports hernia: diagnosis and therapeutic approach. J Am Acad Orthop Surg. 2007;15(8):507-14.

124. Sartelli M, Viale P, Catena F, et al. 2013 WSES guidelines for management of intra-abdominal infections. World J Emerg Surg. 2013;8(1):3.

125. Gans SL, Pols MA, Stoker J, et al. Guideline for the diagnostic pathway in patients with acute abdominal pain. Dig Surg. 2015;32(1):23-31.

126. Gerhardt RT, Nelson BK, Keenan S, et al. Derivation of a clinical guideline for the assessment of nonspecific abdominal pain: the Guideline for Abdominal Pain in the ED Setting (GAPEDS) Phase 1 Study. Am J Emerg Med. 2005;23(6):709-17.

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128. Reust CE, Williams A. Acute Abdominal Pain in Children. Am Fam Physician. 2016;93(10):830-6.

129. Howell JM, Eddy OL, Lukens TW, et al. Clinical policy: Critical issues in the evaluation and management of emergency department patients with suspected appendicitis. Ann Emerg Med. 2010;55(1):71-116.

130. Smith MP, Katz DS, Lalani T, et al. ACR Appropriateness Criteria right lower quadrant pain — suspected appendicitis. Ultrsound Q. 2015;31(2):85-91.

131. Yamamoto W, Kono H, Maekawa M, et al. The relationship between abdominal pain regions and specific diseases: an epidemiologic approach to clinical practice. J Epidemiol. 1997;7(1):27-32.

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139. Gaddey HL, Holder K. Unintentional weight loss in older adults. Am Fam Physician. 2014;89(9):718-22.

140. Stajkovic S, Aitken EM, Holroyd-Leduc J. Unintentional weight loss in older adults. Cmaj. 2011;183(4):443-9.

141. Wong CJ. Involuntary weight loss. Med Clin North Am. 2014;98(3):625-43.

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Codes

The following code list is not meant to be all-inclusive. Authorization requirements will vary by health plan. Please consult the applicable health plan for guidance on specific procedure codes.

Specific CPT codes for services should be used when available. Nonspecific or not otherwise classified codes may be subject to additional documentation requirements and review.

CPT/HCPCS

CPT® (Current Procedural Terminology) is a registered trademark of the American Medical Association (AMA). CPT® five digit codes, nomenclature and other data are copyright by the American Medical Association. All Rights Reserved. AMA does not directly or indirectly practice medicine or dispense medical services. AMA assumes no liability for the data contained herein or not contained herein.

72192	CT pelvis without contrast
72193	CT pelvis with contrast
72194	CT pelvis without contrast, followed by re-imaging with contrast
72195	MRI pelvis without contrast
72196	MRI pelvis with contrast
72197	MRI pelvis without contrast, followed by re-imaging with contrast
74150	CT abdomen without contrast
74160	CT abdomen with contrast
74170	CT abdomen without contrast, followed by re-imaging with contrast
74176	CT abdomen and pelvis without contrast
74177	CT abdomen and pelvis with contrast
74178	CT abdomen and pelvis without contrast in one or both body regions, followed by re-imaging with contrast
74181	MRI abdomen without contrast
74182	MRI abdomen with contrast
74183	MRI abdomen without contrast, followed by re-imaging with contrast
74712	MRI fetal, including placental and maternal pelvic imaging when performed, single or first gestation
74713	MRI fetal, including placental and maternal pelvic imaging when performed, each additional gestation (List separately in addition to code for primary procedure)
76391	Magnetic resonance (e.g., vibration) elastography
S8037	Magnetic resonance cholangiopancreatography (mrcp)
0648T	Quantitative magnetic resonance for analysis of tissue composition (eg, fat, iron, water content), including multiparametric data acquisition, data preparation and transmission, interpretation and report, obtained without diagnostic MRI examination of the same anatomy (eg, organ, gland, tissue, target structure) during the same session
0649T	Quantitative magnetic resonance for analysis of tissue composition (eg, fat, iron, water content), including multiparametric data acquisition, data preparation and transmission, interpretation and report, obtained with diagnostic MRI examination of the same anatomy (eg, organ, gland, tissue, target structure) (List separately in addition to code for primary procedure)

ICD-10 Diagnosis

Refer to the ICD-10 CM manual

History

Status	Review Date	Effective Date	Action
Updated	01/23/2024	Unchanged	Expanded guideline rationale. Added required language per new Medicare regulations.
Revised	05/09/2022	04/09/2023 for commercial, Medicare, and Medicaid except LA; 06/18/2023 for LA Medicaid	Independent Multispecialty Physician Panel (IMPP) review. Revised the following indications: Uterine leiomyomata, Pancreatic mass, indeterminate cystic, Pancreatitis, Pelvic floor disorders, and Abdominal and/or pelvic pain. Added indication for Pancreatic duct dilation.
Revised	05/26/2021	03/13/2022 for Commercial, Medicare, and Medicaid except Simply Healthcare (Florida Medicaid); 09/11/2022 for Simply Healthcare (Florida Medicaid).	IMPP review. Revised the following indications: Uterine artery embolization procedures, Diffuse liver disease, Jaundice, Sacroiliitis, Pancreatic mass, Pancreatitis, Hematuria, Polycystic kidney disease, Renal mass, and Urinary tract calculi. Removed Intussusception and Azotemia. Added CPT codes 0648T and 0649T.
Revised	05/26/2021	11/07/2021 for Commercial, Medicare and non-Anthem Medicaid; 03/13/2022 for Anthem Medicaid except Simply Healthcare (Florida Medicaid); 09/11/2022 for Simply Healthcare (Florida Medicaid).	IMPP review. Added Transplant-related imaging.
Revised	–	03/14/2021	Added HCPCS code S8037.
Revised	06/10/2019	02/09/2020	IMPP review. Revised the following indications: Enteritis or colitis, Foreign body (pediatric only), GI bleeding, Henoch-Schonlein purpura, Inflammatory bowel disease, Intussusception (pediatric only), Ischemic bowel, Hematoma or hemorrhage, Perianal fistula/abscess, Ascites, Biliary tract dilatation or obstruction, Cholecystitis, Choledocholithiasis, Diffuse liver disease, Focal liver lesion, Hepatomegaly, Jaundice, Pancreatic mass, Adrenal mass indeterminate, Hematuria, Renal mass, Urinary tract calculi, Splenic mass benign, Splenic mass indeterminate, Splenomegaly, Adrenal hemorrhage, Adrenal mass, Lymphadenopathy, Splenic hematoma, Undescended testicle, Abdominal pain, Lower extremity edema, and Pelvic pain. Moved Azotemia and Adrenal mass to Renal/adrenal indications, Splenomegaly to Splenic indications, and Prostate cancer to Oncologic imaging. Added CPT code 76391.
Restructured	09/12/2018	01/01/2019	IMPP review. Advanced Imaging guidelines redesigned and reorganized to a condition-based structure. Incorporated AIM guidelines for pediatric imaging.
Revised	07/11/2018	03/09/2019	IMPP review. Renamed the Administrative Guidelines to “General Clinical Guideline.” Retitled Pretest Requirements to “Clinical Appropriateness Framework” to summarize the components of a decision to pursue diagnostic testing. Revised to expand applicability beyond diagnostic imaging, retitled Ordering of Multiple Studies to “Ordering of Multiple Diagnostic or Therapeutic Interventions” and replaced imaging-specific terms with “diagnostic or therapeutic intervention.” Repeated Imaging split into two subsections, “repeat diagnostic testing” and “repeat therapeutic intervention.”
Revised	03/01/2018	10/29/2018	IMPP review. Lowered threshold for unexplained weight loss and more explicitly defined preliminary work up in CT abdomen/CT pelvis/CT abdomen and pelvis. Added hemochromatosis as an indication for MRI abdomen in pediatric patients.
Created	–	03/30/2005	Original effective date.