Transient Hepatic Attenuation Differences in Computed Tomography from Extrahepatic Portal Vein Compression

OBJECTIVE: To describe the appearance of transient hepatic attenuation differences (THADs) of extrahepatic origin. MATERIALS AND METHODS: Five cases of THADs produced by compression of the extrahepatic portal vein at its confluence with the splenic vein were identified prospectively over a four-month period. Two additional cases of peripheral THADs resulting from main portal vein thrombosis were identified from retrospective review of a departmental database. RESULTS: Streamlining of portal venous flow resulted primarily in left lobar THADs when the portal vein is compressed at its confluence with the splenic vein. THADs were seen in the periphery of the liver in the two cases of main portal vein thrombosis. CONCLUSION: Lobar and/or peripheral THADs can be produced by compromise of splenic and extrahepatic portal venous flow. Radiologists should be familiar with the “central pseudotumor” created by the peripheral THAD that can result from portal vein thrombosis.