Focal sparing of segment IV in fatty livers shown by sonography and CT: correlation with aberrant gastric venous drainage.

Abstract

One of the most common sites of focal sparing in fatty livers (focal spared area) shown by sonography or CT is the posterior edge of segment IV. The differentiation of such a focal spared area from tumor has been a diagnostic challenge. The purpose of this study was to determine if a correlation exists between the focal spared area at the posterior edge of segment IV in fatty liver and the decrease of portal perfusion from the main portal vein due to aberrant gastric venous drainage directed into segment IV. Seventeen patients with fatty liver diagnosed on the basis of sonographic and CT findings who had hepatic arteriography and/or CT during arterial portography (CTAP) were included in the study. Seven patients had a focal spared area more than 2 cm in the longest diameter at the posterior edge of segment IV, and 10 patients did not have a focal spared area. The frequency of aberrant gastric venous drainage shown by arteriography (17 patients) and/or by CTAP (15 patients) was compared in the two groups of patients. Hepatic arteriography showed aberrant gastric venous drainage in all patients who had a spared area, and CTAP showed a portal perfusion defect at the posterior edge of segment IV in all five patients with a focal spared area who underwent CTAP. On the other hand, no definite aberrant gastric venous drainage and portal perfusion defect were seen in any patient without a spared area. The difference in the frequency of aberrant gastric venous drainage between the two groups of patients was statistically significant (chi-square test, p < .0001). Our results show that a strong correlation exists between the focal spared area at the posterior edge of segment IV in fatty liver and aberrant gastric venous drainage directed to segment IV. Focally decreased blood flow from the main portal vein associated with aberrant gastric venous drainage is a likely cause of the focal spared area. This fact is important for the differential diagnosis of hepatic tumors.