LCD L34415: CT of the Abdomen and Pelvis

A computed tomographic (CT) image is a display of the anatomy of a thin slice of the body developed from multiple x-ray absorption measurements made around the periphery of the body. Unlike conventional tomography, where the image of a thin section is created by blurring out the information from unwanted regions, the CT image is constructed mathematically using data arising only from the section of interest. Generating such an image is confined to cross sections of the anatomy that are oriented essentially perpendicular to the axial dimensions of the body. Reconstruction of the final image can be accomplished in any plane.

Abdominal CT

The CT of the abdomen extends from the dome of the diaphragm to the pelvic brim or pubic symphysis, depending upon whether one groups the pelvis with the abdomen or treats it separately.

A CT scan of the abdomen will be considered medically reasonable and necessary under the following circumstances 2 :

• Evaluation of abdominal pain 3,8,9

• Evaluation of known or suspected abdominal masses or fluid collections

• Evaluation of primary or metastatic malignancies

• Evaluation of abdominal inflammatory processes

• Evaluation of abnormalities of abdominal vascular structures (Note: Medical necessity for CT angiography is not addressed in this LCD)

• Evaluation of abdominal trauma

• Clarification of findings from other imaging studies of the abdomen or laboratory abnormalities suggesting abdominal pathology

• Guidance for interventional diagnostic or therapeutic procedures within the abdomen

• Treatment planning for radiation therapy

• For patients being evaluated for potential transcatheter aortic valve implantation/replacement (TAVI or TAVR) provided that the patient has not undergone a CT of the abdomen within the preceding 60 days 1,4,6

Pelvic CT

The CT scan of the pelvic area includes all pelvic structures including the bladder, the prostate in males, ovaries, uterus, and uterine adnexa in females, and the lower retroperitoneum, and iliac lymph node chains. The CT scan of the pelvis is useful in evaluating cysts, tumors, masses, metastases to one or more of these organs, and iliac lymph nodes. Intravenous contrast material may be administered.

A CT scan of the pelvis will be considered medically necessary and reasonable under the following circumstances 2 :

• Evaluation of cysts, tumors, or masses of the pelvic structure (i.e., that which lies at or below the pelvic brim or true pelvis)

• Evaluation of metastasis of primary cancers to this region

• Evaluation of inflammatory processes in this region

• Evaluation of abnormalities of pelvic vascular structures

• Evaluation of lymphadenopathies of this region

• Evaluation of lower abdominal, generalized abdominal or pelvic pain 3,8,9

• Evaluation of other genitourinary (GU) disorders in which the physician cannot make a diagnosis on physical examination and/or by ultrasound (US)

• Evaluation of trauma to the pelvic structure/organs

• Evaluation of the effectiveness of a radiation treatment plan

• For patients being evaluated for potential TAVI or TAVR provided that the patient has not undergone a CT of the pelvis within the preceding 60 days. 1,4,6

Intravenous contrast material may be administered with any of the above studies.

In addition to the medical necessity requirements, the CT scan must be performed on a model of CT equipment that meets the following criteria:

• The model must be known to the Food and Drug Administration (FDA); and

• Must be in the full market release phase of development.

The American College of Radiology (ACR) (2016) published its practice parameters for the performance of CT of the abdomen and pelvis. 2 This publication includes the indications for abdominal and/or pelvic CT examinations. In 2018, Scheirey et al published the ACR Appropriateness Criteria ® for nonlocalized abdominal pain. 9 This review focused on imaging the adult population with nonlocalized abdominal pain, including patients with fever, recent abdominal surgery, or neutropenia. The authors concluded that imaging of the entire abdomen and pelvis to evaluate for infectious or inflammatory processes of the abdominal viscera and solid organs, abdominal and pelvic neoplasms, and screen for ischemic or vascular etiologies is essential for prompt diagnosis and treatment. The authors state that computed tomography, which is often the first-line modality, quickly evaluates the abdomen/pelvis, providing for accurate diagnoses and management of patients with abdominal pain. Furthermore, while often performed, abdominal radiographs may not alter management.

Haller et al (2010) performed a retrospective review to evaluate whether non-contrast CT (NCT) provided more diagnostic information than abdominal plain film (APF) in patients that presented with acute non-traumatic abdominal pain. 3 The authors also addressed if use of CT could reduce the total number of additional radiograms. A total of 222 patients were retrospectively reviewed. 86 patients had APF, 60 had standard-dose CT (SDCT), and 76 had low-dose CT (LDCT). The radiological report of each patient was compared with the final diagnosis obtained from the medical record within 30 days. Additional radiograms were registered, and a total radiation dose excluding or including APF or NCT was calculated. Results showed that NCT gave a correct diagnosis in 50% compared to 20% with APF (P radiograms was substantially lower in the CT group compared to the APF group (P

Pandharipande et al (2016) conducted a prospective study to determine how the diagnoses, diagnostic uncertainty, and management decisions of physicians are affected by the results of CT in the emergency department (ED). 8 Physicians were surveyed before and after CT to determine the leading diagnosis, diagnostic confidence, alternative “rule out” diagnosis, and management decisions. Primary measures were the proportion of patients for whom the leading diagnosis or admission decision changed and median changes in diagnostic confidence. Secondary measures addressed alternative diagnoses and return-to-care visits (e.g., to emergency department) at 1-month follow-up. The leading diagnosis changed in 235 of 460 patients with abdominal pain (51%). Pre-CT diagnostic confidence was inversely associated with the likelihood of a diagnostic change ( P 0.0001). Median post-CT confidence was 95%. CT helped confirm or exclude at least 95% of alternative diagnoses. Admission decisions changed in 116 of 457 patients with abdominal pain (25%). During follow-up, 70 of 450 patients with abdominal pain (15%) returned for the same indication. The authors concluded that physicians’ diagnoses and admission decisions changed frequently after CT. Diagnostic uncertainty was alleviated.

Multiple publications (Achenbach et al, 2012; Hawkey et al, 2014; Leipsic et al, 2011) have described the important role CT plays in screening protocols of patients who are candidates for transcatheter aortic valve implantation (TAVI) or transcatheter aortic valve replacement (TAVR). 1,4,6 CT imaging provides information on the suitability of the peripheral access vessels and accurate dimensions of the involved vasculature and aortic annulus, which assists in sizing of the prosthesis.