Nontumorous low-attenuation defects in the liver on helical CT during arterial portography: Frequency, location, and appearance

OBJECTIVE. Low-attenuation defects in the liver that are caused by variations in the portal perfusion of the liver rather than by intrahepatic tumor can be detected using helical CT during arterial portography (CTAP). The purpose of this study was to characterize these nontumorous low- attenuation defects detected with helical CTAP in terms of their frequency, location, and appearance. MATERIALS AND METHODS. Helical CTAP examinations of 89 patients referred for preoperative evaluation of metastatic or primary liver tumors performed over a 20-month period were retrospectively reviewed by three radiologists. The frequency, appearance, and location of focal (within a subsegment) and diffuse (affecting more than one subsegment) nontumorous perfusion defects were determined. Findings on helical CTAP images were correlated with surgical findings (53 patients), results of MR examinations (25 patients), and follow-up CT examinations (11 patients). RESULTS. Ninety-seven nontumorous perfusion defects were identified in 68 patients. The most frequent defects were located adjacent to the gallbladder fossa (35), anterior to the porta hepatis (34), in the subcapsular portion of the liver (13), and adjacent to the falciform ligament (12). Nontumorous perfusion defects characteristically appeared wedge-shaped or flat and ranged in size from 8-20 mm. CONCLUSION. Nontumorous perfusion abnormalities have characteristic appearances and locations on helical CTAP examinations and are more common than previously reported with conventional CTAP. Familiarity with the locations and characteristic appearances of these defects is essential to prevent false-positive diagnoses, so that operative candidates are not mistakenly denied surgical therapy.