Transient perihilar attenuation difference in the liver on dynamic CT secondary to portal vein thrombosis: report of two cases.

In two patients with portal vein thrombosis (PVT) accompanied by cavernous transformation, transient perihilar attenuation difference (TPAD) was demonstrated in the liver in the arterial phase of dynamic CT. It changed to an isodense shadow in the late phase. In one case, the area demonstrated as TPAD was well enhanced by postarterial portal CT, and in the other case, perihilar region was also densely opacified as contrasted by the peripheral area which was enhanced slightly with postarterial portography. It suggested that the TPAD area well supplied by portal blood flow via cavernous transformation and that the peripheral area surrounding TPAD was mainly supplied by increased hepatic arterial blood compensating for reduced portal flow. When the TPAD is found in the early phase of dynamic CT scan, attention should be paid to the existence of portal vein thrombosis (PVT). Chronic pancreatitis was the likely cause in one patient, and in the other it was idiopathic.