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. Use of the Guidelines by any external AI entity without the express written permission of Carelon is prohibited.

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.

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 and has moderate to high diagnostic accuracy in patients with subacute unexplained gastrointestinal bleeding. Ultrasound is the initial modality for evaluation of congenital hepatobiliary disease.¹ 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. Renal scintigraphy can be useful to establish the diagnosis of congenital anomalies of the kidney and ureter or for differential estimation of renal function, especially in the presence of an ectopic, malrotated, or hypoplastic kidney.

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.

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 not addressed elsewhere

IMAGING STUDY

ADULT

Ultrasound required for initial evaluation of a palpable pelvic mass in patients assigned female at birth, or for testicular masses in patients assigned male at birth
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

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 in EITHER of the following scenarios:

Diagnosis of clinically suspected endometriosis following nondiagnostic pelvic ultrasound
Management of established endometriosis

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^3-5 with advanced imaging reserved in select cases as an add-on test to further characterize abnormalities on ultrasound or when ultrasound is nondiagnostic. Evidence-based guidelines recommend against the use of pelvic MRI as the primary method of investigation when endometriosis is clinically suspected.⁶ However, when further evaluation is needed following ultrasound, MRI is the advanced imaging modality of choice due to its superior soft tissue contrast.⁴

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.⁷

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 in the second or third trimester of pregnancy, 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

Note: fertility-sparing procedures include but are not limited to myomectomy and uterine artery embolization, regardless of whether the procedure is being performed with the specific intent of preserving fertility

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.⁹

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.¹⁰

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.¹¹

In a prospective cohort study of patients aged 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.¹² 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.¹³

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.^{14, 15}

Bowel obstruction

Advanced imaging is considered medically necessary for diagnosis and management.

IMAGING STUDY

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. 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.¹⁶ 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.

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.¹⁷ 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. 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. Evidence-based guidelines recommend against the routine use of imaging for evaluation of chronic constipation in adult patients.¹⁷

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.^{18, 19} There is a lack of clinical data to support the use of MRI as a first-line modality in the diagnosis of diverticulitis.²⁰

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.²¹

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.²²

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.

Calprotectin is a protein released by activated neutrophils, and elevated fecal levels are associated with inflammatory or malignant disease within the colon. 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).²³ 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.²⁴

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.

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, ²⁶ 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.²⁶

Hepatobiliary Indications

Biliary tract dilatation or obstruction

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

Unexplained biliary tract dilation
Biochemical evidence of biliary obstruction following nondiagnostic ultrasound
Annual evaluation of patients with Caroli disease or Caroli syndrome

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.¹ 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.^27, ^28, ^{29, 30}

A 2022 guideline from the European Association for the Study of the Liver recommends annual MRCP in patients with Caroli disease and Caroli syndrome, as surveillance for cholangiocarcinoma; they report a 7% prevalence of cholangiocarcinoma in this population compared to 0.05% in the general population. ³¹

Cholecystitis

Advanced imaging is considered medically necessary 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.^, ^1, 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.³²

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.³³

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.^29, ^30, ³³

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^{29, 34,} ^30, ³³ 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.^{28, 30} 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).³⁵

Diffuse liver disease

Includes chronic hepatitis, cirrhosis, glycogen storage diseases, hemochromatosis, and Wilson’s disease. For hepatocellular cancer screening in high-risk patients, see the Oncologic Imaging guidelines.

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

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
Assessment of hepatic fibrosis/cirrhosis in patients with established 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 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 assessment of hepatic fibrosis/cirrhosis

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.³⁶

Limited data is available comparing accuracy of available cross-sectional imaging modalities. ^37-40 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. 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.

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 also of 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 ⁴¹ and guidelines from the American College of Radiology characterize MR elastography as generally appropriate for diagnosis of hepatic fibrosis.³⁶ Multiple recent systematic reviews have shown high diagnostic accuracy for MR elastography comparable⁴² to marginally greater 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.^43, ^, In addition, the diagnostic accuracy of MR elastography is similar regardless of the underlying etiology of chronic liver disease. A 2022 clinical practice guideline from the American Association of Clinical Endocrinology preferentially recommends vibration-controlled transient elastography (VCTE) in the diagnosis of NAFLD with significant fibrosis, but also indicates that MR elastography, while it has limited availability, is the most accurate. (Grade B recommendation, intermediate strength of evidence) This guideline further states that MRE has been studied in pediatric patients with NAFLD and found to have a PPV for the presence of fibrosis of 74-76%, but “pediatric-specific norms have not yet been developed for NAFLD.”⁴⁴ 2023 systematic review and meta-analysis reported that for evaluation of liver fibrosis, the pooled sensitivity and specificity for MRE were 94% and 95% respectively, compared to 86% and 88% for point-shear wave elastography.⁴⁵

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. In the setting of classic imaging findings and low risk for hepatic malignancy, ultrasonography is often sufficient. Otherwise, further evaluation with MRI should be considered.

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),^, thus close clinical follow up and monitoring for progression may be the most appropriate next step. In an otherwise healthy patient, an incidentally discovered focal liver lesion has an estimated probability of greater than 95% of being benign.

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. ⁴⁶

In terms of appropriate follow up, the American Association for the Study of Liver Diseases, as part of 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. 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).⁴⁷

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.²⁷

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. 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.⁴⁸ 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.

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).

Axial spondyloarthropathy

Includes ankylosing spondylitis, reactive arthritis, psoriatic arthritis, spondyloarthropathy associated with inflammatory bowel disease, and juvenile-onset spondylarthritis

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

Suspected spondyloarthropathy (SpA) when BOTH of the following are present:
- Radiographs negative or equivocal for sacroiliitis
- Inflammatory back pain* for at least 3 months
Baseline prior to therapy when diagnosis based on radiographic findings (no prior MRI)
Re-evaluation following at least 3 months of tumor necrosis factor inhibitors, without clinical improvement

*Inflammatory back pain characteristically includes the following features: insidious onset, improvement with exercise, no improvement with rest, occurring at night, and age of onset < 40 years of age.

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.⁴⁹ 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.⁵⁰

There is consensus among guidelines that radiography of the pelvis and/or spine is the preferred imaging modality for initial evaluation of spondyloarthritis.⁵¹ Radiographs of the whole spine are recommended as the first-line imaging modality.⁵² 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.⁵³ 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.⁵⁴

Consensus among guidelines is that MRI should be obtained in patients with persistent clinical suspicion when radiography is negative or indeterminate.⁵⁴ When radiographs are negative and there is suspicion of spondyloarthritis, MRI is mandatory to look for early inflammatory lesions.⁵² 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.

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

ADULT

Advanced imaging is considered medically necessary following nondiagnostic radiographs.

PEDIATRIC

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.

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.⁵⁵

The American College of Radiology Appropriateness Criteria indicates that for initial imaging evaluation of suspected osteomyelitis or septic arthritis, CT and MRI are both 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.⁵⁶

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^, ^55, 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,⁵⁶ 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:

Suspected sacral insufficiency fracture
Suspected stress fracture or traumatic fracture, following nondiagnostic pelvic or sacral radiographs

IMAGING STUDY

CT or MRI pelvis

Sacroiliitis, not otherwise specified

Advanced imaging is considered medically necessary 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.^52-54

Septic arthritis

ADULT

Advanced imaging is considered medically necessary following nondiagnostic radiographs.

PEDIATRIC

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 (including suspected 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 in EITHER of the following scenarios:
- Every other year for up to 4 years if not increasing in size
- Every 12 months if enlarging
Cysts less than 1.5 cm in a patient of age less than 80 at the time of diagnosis
- 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 in a patient of age less than 80 at the time of diagnosis
- 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.⁵⁷ 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.⁵⁷ 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
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. Therefore, CT is not indicated and should not be ordered routinely for patients with mild acute pancreatitis.⁵⁸

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).²⁸ 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.⁵⁹

Renal, Adrenal, and Urinary Tract Indications

Adrenal mass, indeterminate

Indeterminate masses are those not already demonstrating benign imaging features. For patients with known adrenal neoplasm or malignancy, see Oncologic imaging guidelines.

ADULT

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

Biochemical evidence of a functional adrenal mass
Indeterminate adrenal mass identified on ultrasound
Indeterminate adrenal mass identified on CT/MRI (with no other prior imaging):
- 1-2 cm, single 12-month follow-up
- >2 cm and <4 cm
New or enlarging adrenal mass (when compared to prior imaging)

*Incidental masses ≥ 4 cm may be referred for resection rather than CT/MRI.

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.⁶⁰ For indeterminate lesions 2 cm or less without prior imaging or known primary malignancy, 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.^60, ^{61, 62} No follow up is recommended for lesions with benign features ^{63, 64}, 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%).⁶³ 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.⁶³

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 (painless or undifferentiated)

For hematuria with pain or other symptoms, see indications for Urinary Tract Calculus or Pyelonephritis

ADULT

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

Traumatic hematuria
Macroscopic hematuria
Microscopic hematuria in EITHER of the following scenarios:
- High-risk patients (defined as ANY of the following):
  - Age ≥ 60 years
  - More than 30 pack year smoking history
  - More than 25 red blood cells per high powered field (RBC/HPF) on urinalysis
  - History of gross hematuria
- 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. Advanced imaging is helpful to exclude malignancy in select scenarios and changes management in up 53% of patients.⁶⁵

Incidence of malignancy is lower in patients presenting with asymptomatic atraumatic microscopic hematuria, typically defined as 3 or more 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. ⁶⁶ Examples of benign causes include vigorous exercise, UTI, recent menstruation, known medical renal disease, and recent urological procedures. In patients with a known benign cause and with no risk factors, guidelines indicate that a complete workup for microscopic hematuria is unlikely to be beneficial.⁶⁶ 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 pretest 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.⁶⁷

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.⁶⁸

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.⁶⁶ MR urography is an option that may be considered as an add on test when contrast enhanced CT is contraindicated.⁶⁹

Hydronephrosis

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

IMAGING STUDY

CT abdomen or CT abdomen/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.⁷⁰ 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 ⁷¹, although MRI may be useful in pediatric or radiation-sensitive populations.

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 ANY of the following scenarios:

Initial evaluation of an indeterminate renal mass in ANY of the following scenarios:
- 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
Known renal mass and a genetic or medical predisposition to renal cancer
Known solid benign renal mass, with new or worsening symptoms
Surveillance of previously imaged renal masses in ANY of the following scenarios:
- 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.⁷² Renal cysts classified Bosniak category I or II require no follow up and include simple cysts, cysts with thin septa and hemorrhagic cysts.⁷³ 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 thereafter, especially in patients who are poor surgical candidates or who have limited life expectancy.⁷² ⁷⁴

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 potential⁷⁵ 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:

Suspected calculus in patients with no history of nephrolithiasis
History of nephrolithiasis with suspected recurrence* when ANY of the following apply:
- History of radiolucent calculus
- History of radiopaque calculus with atypical presentation
- History of radiopaque calculus and EITHER of the following scenarios:
  - In patients less than age 50, following nondiagnostic ultrasound
  - In patients 50 years of age or greater
Management/follow up of known calculi when ANY of the following apply:
- Known radiolucent calculi
- Following nondiagnostic KUB or ultrasound, or ultrasound with hydronephrosis
- Symptomatic patients following ureteroscopic stone extraction
- Planned intervention (eg percutaneous nephrolithotomy, ureteroscopy, or shock wave lithotripsy), when CT has not been performed within the preceding 30 days
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.^{76, 77} CT detects important incidental findings in patients over 80 years of age in 28.9% of cases. 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.

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. Use of CT prior to percutaneous nephrolithotomy (PCNL) is a strong recommendation based on low quality evidence from the American Urological Association (AUA).⁷⁸ 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 ureteroscopy⁷⁸ 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”.⁷⁶ 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.⁷⁶

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.⁷⁶

Splenic Indications

Splenic mass

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 or rapid growth
Features suspicious for malignancy (ANY of the following):
- Heterogenous enhancement
- Irregular margins
- Necrosis
- Multiple lesions
- Extension beyond the margin of the spleen
Surveillance of indeterminate mass: 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.⁷⁹

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 ANY of the following scenarios:

Suspected groin hernia, following nondiagnostic ultrasound
Suspected hernia complications (including postoperative)
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

Rationale

While clinical examination and ultrasound are often the preliminary evaluation methods of choice, CT can assist in the differential diagnosis of hernia vs other abdominal wall mass.⁸⁰ It is useful in surgical planning to define the abdominal wall anatomy in non-midline hernias such as those on the flanks, suprapubic or subxiphoid regions, and to identify posterior abdominal wall defects.⁸¹ Guidelines recommend clinical examination combined with ultrasound to evaluate for possible occult groin hernia. MRI or CT is suggested for groin hernias when ultrasound is nondiagnostic. Sensitivity and specificity for MRI are 94.5% and 96.3%, respectively, compared to 77% and 86%, respectively, for ultrasound.⁸²

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.⁷⁹

Pelvic floor disorders

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

Functional disorder of the pelvic floor associated with urinary or bowel incontinence
Physical examination findings suspicious for pelvic organ prolapse
Chronic constipation when anorectal manometry or balloon expulsion tests are nondiagnostic

IMAGING STUDY

MRI pelvis (Dynamic MRI (MR defecography) technique is preferred)^83-85

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

Perioperative evaluation, not otherwise specified

Transplant-related imaging

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

For living donors, a single pre-transplant evaluation
For patients on the transplant waiting list for liver transplantation, annual surveillance
Single evaluation prior to lung, kidney, or hematopoietic stem cell transplantation
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

Bariatric procedure-related imaging

Advanced imaging is considered medically necessary for suspected complication (including postoperative leaks, bowel obstruction, and internal hernias) following bariatric procedures.

IMAGING STUDY

CT abdomen or CT abdomen/pelvis

Rationale

The most commonly performed bariatric surgery worldwide is sleeve gastrectomy (SG), followed by Roux-en Y gastric bypass (RYGB) and one-anastomosis gastric bypass. Additional bariatric procedures include biliopancreatic diversion with duodenal switch, single-anastomosis duodenal switch, endoscopic sleeve gastroplasty, and intragastric balloons.

Nonspecific Signs and Symptoms

Abdominal and/or pelvic pain, undifferentiated

Note: Abdominal pain should be evaluated in the context of a differential diagnosis based on findings from history, physical exam, and relevant lab results. 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 ANY of the following scenarios:

Pain associated with clinical findings of a surgical abdomen or guarding on exam
Pain that remains unexplained after ALL of the following:
- History and physical exam
- Relevant labs*
- Ultrasound if pain is localized to the right upper quadrant (abdominal ultrasound), female pelvis (pelvic ultrasound), or testicles (scrotal ultrasound)
- Upper endoscopy for chronic epigastric pain 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:

Pain associated with clinical findings of a surgical abdomen or guarding on exam
Pain that remains unexplained after ALL of the following:
- History
- Physical exam
- Relevant lab results*
- Abdominal or pelvic ultrasound
Pelvic or testicular pain following nondiagnostic ultrasound

*Preliminary lab tests may include metabolic profile, complete blood count (CBC), C-reactive protein (CRP), erythrocyte sedimentation rate (ESR), and/or urinalysis.

IMAGING STUDY

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

Rationale

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. ⁸⁶ CT is also the single best diagnostic adjunct to augment the clinical exam. 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.³ Ultrasound is recommended in the initial evaluation of right upper quadrant pain, since the pain is often hepatobiliary in origin²⁷ (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.^87, ^88, ¹⁵ Ultrasound is also indicated for initial evaluation of acute onset scrotal pain.⁸⁹

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 symptoms, 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.⁹⁰ Advanced imaging may be helpful in patients with significantly elevated WBC or ESR, as the positive predictive value for intra-abdominal pathology is high.⁹¹ 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 average, 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.⁹²

In pediatric patients with unexplained, nonspecific atraumatic abdominal pain, CT is not always necessary. Ultrasound is suggested as an initial imaging modality⁹³, 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). The American Academy of Pediatrics also recommends further evaluation in patients with red flag features including 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.⁹⁴

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. Lymphoscintigraphy can help to determine whether obstruction to lymphatic flow is responsible for diffuse swelling and help to direct both medical and surgical interventions.

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.⁹⁵ Weight loss is not uncommon in elderly patients and is typically related to one of the 9 Ds: dementia, dentition, depression, diarrhea, drugs, functional dysfunction, dysgeusia (altered taste), or dysphagia. When unintentional weight loss remains unexplained, it may be due to the 9^th D: acute or chronic disease. Initial evaluation should include a clinical examination including laboratory studies, chest radiography, and where clinically appropriate, abdominal ultrasonography.⁹⁵

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.⁹⁶ 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.

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63. Fassnacht M, Tsagarakis S, Terzolo M, et al. European Society of Endocrinology clinical practice guidelines on the management of adrenal incidentalomas, in collaboration with the European Network for the Study of Adrenal Tumors. Eur J Endocrinol. 2023;189(1):G1-g42. PMID 37318239

64. Lee JM, Kim MK, Ko SH, et al. Clinical guidelines for the management of adrenal incidentaloma. Endocrinol Metab (Seoul). 2017;32(2):200-18. PMID 28685511

65. 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. PMID 27479641

66. Wolfman DJ, Marko J, Nikolaidis P, et al. ACR Appropriateness Criteria hematuria. J Am Coll Radiol. 2020;17(5s):S138-s47. PMID 32370958

67. Barocas DA, Boorjian SA, Alvarez RD, et al. Microhematuria: AUA/SUFU guideline. J Urol. 2020;204(4):778-86. PMID 32698717

68. 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. PMID 29724430

69. Barocas DA, Lotan Y, Matulewicz RS, et al. Updates to microhematuria: AUA/SUFU guideline (2025). J Urol. 2025;213(5):547-57. PMID 40013563

70. 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. PMID 29427476

71. Whitworth P, 3rd, Courtney KG, Oto A, et al. ACR Appropriateness Criteria hydronephrosis on prior imaging-unknown cause. J Am Coll Radiol. 2024;21(6s):S144-s67. PMID 38823942

72. 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. PMID 28651987

73. Richard PO, Violette PD, Bhindi B, et al. 2023 update – Canadian Urological Association guideline: management of cystic renal lesions. Can Urol Assoc J. 2023;17(6):162-74. PMID 37310905

74. Campbell SC, Clark PE, Chang SS, et al. Renal mass and localized renal cancer: evaluation, management, and follow-up: AUA guideline: part I. J Urol. 2021;206(2):199-208. PMID 34115547

75. Malkan AD, Loh A, Bahrami A, et al. An approach to renal masses in pediatrics. Pediatrics. 2015;135(1):142-58. PMID 25452658

76. European Association of Urology (EAU), EAU guidelines on urolithiasis, (2025) Arnehm, EAU, 121 pgs.

77. Gupta RT, Kalisz K, Khatri G, et al. ACR Appropriateness Criteria acute onset flank pain-suspicion of stone disease (urolithiasis). J Am Coll Radiol. 2023;20(11s):S315-s28. PMID 38040458

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

79. 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. PMID 24183552

80. Garcia EM, Pietryga JA, Kim DH, et al. ACR Appropriateness Criteria hernia. J Am Coll Radiol. 2022;19(11s):S329-s40. PMID 36436960

81. Earle D, Roth JS, Saber A, et al. SAGES guidelines for laparoscopic ventral hernia repair. Surg Endosc. 2016;30(8):3163-83. PMID 27405477

82. HerniaSurge Group. International guidelines for groin hernia management. Hernia. 2018;22(1):1-165. PMID 29330835

83. 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. PMID 28755255

84. 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. PMID 32648139

85. Khatri G, Bhosale PR, Robbins JB, et al. ACR Appropriateness Criteria pelvic floor dysfunction in females. J Am Coll Radiol. 2022;19(5s):S137-s55. PMID 35550798

86. 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. PMID 25659265

87. Dahabreh IJ, Adam GP, Halladay CW, et al. Diagnosis of right lower quadrant and suspected acute appendicitis Diagnosis of Right Lower Quadrant Pain and Suspected Acute Appendicitis. Vol. AHRQ Comparative Effectiveness Reviews, Number 157. Rockville (MD): Agency for Healthcare Research and Quality (US); 2015.

88. Diercks DB, Adkins EJ, Harrison N, et al. Clinical policy: critical issues in the evaluation and management of emergency department patients with suspected appendicitis: approved by ACEP Board of Directors February 1, 2023. Ann Emerg Med. 2023;81(6):e115-e52. PMID 37210169

89. Wang CL, Aryal B, Oto A, et al. ACR Appropriateness Criteria acute onset of scrotal pain-without trauma, without antecedent mass. J Am Coll Radiol. 2019;16(5s):S38-s43. PMID 31054757

90. Vij A, Zaheer A, Kamel IR, et al. ACR Appropriateness Criteria epigastric pain. J Am Coll Radiol. 2021;18(11, Supplement):S330-S9. PMID 34794592

91. Gans SL, Atema JJ, Stoker J, et al. C-reactive protein and white blood cell count as triage test between urgent and nonurgent conditions in 2961 patients with acute abdominal pain. Medicine (Baltimore). 2015;94(9):e569. PMID 25738473

92. Moayyedi P, Mearin F, Azpiroz F, et al. Irritable bowel syndrome diagnosis and management: A simplified algorithm for clinical practice. United European Gastroenterol J. 2017;5(6):773-88. PMID 29026591

93. Buel KL, Wilcox J, Mingo PT. Acute abdominal pain in children: evaluation and management. Am Fam Physician. 2024;110(6):621-31. PMID 39700366

94. American Academy of Pediatrics Subcommittee on Chronic Abdominal Pain. Chronic abdominal pain in children. Pediatrics. 2005;115(3):812-5. PMID 15741394

95. Gaddey HL, Holder KK. Unintentional weight loss in older adults. Am Fam Physician. 2021;104(1):34-40. PMID 34264616

96. Bosch X, Monclus E, Escoda O, et al. Unintentional weight loss: clinical characteristics and outcomes in a prospective cohort of 2677 patients. PLoS One. 2017;12(4):e0175125. PMID 28388637

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
Revised	07/17/2025	04/04/2026	Independent Multispecialty Physician Panel (IMPP) review. Revised the following indications: Bowel obstruction, Diffuse liver disease, Axial spondyloarthropathy, Adrenal mass, indeterminate, Hematuria (painless or undifferentiated), Urinary tract calculi, Hernia, and Abdominal and/or pelvic pain, undifferentiated. Removed indication for Sports hernia and added new indication for Bariatric procedure-related imaging.
Revised	07/16/2024	03/23/2025 except for Healthy Blue LA Medicaid, Simply Healthcare FL Medicaid; 04/20/2025 for Premera; 05/18/2025 for Regence	IMPP review. Revised the following indications: Tumor or Neoplasm- not otherwise specified, Endometriosis, Obstetric Indications, Diffuse liver disease, Pancreatic mass, indeterminate cystic (including suspected IPMN.IPMT), and Abdominal and/or pelvic pain, undifferentiated.
Revised	07/18/2023	04/14/2024 for commercial, Medicare, and Medicaid except LA	IMPP review. Revised the following indications: Biliary tract dilation or obstruction, Diffuse liver disease, Osteomyelitis, Septic arthritis, Pancreatic mass, indeterminate cystic, Pelvic floor disorders, and Transplant-related imaging.
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	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	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	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.