Vascular plexus around intrahepatic bile ducts in normal livers and portal hypertension

Vessels around the intrahepatic large bile ducts (peribiliary vascular plexus) were examined by histologic, immunohistochemical and scanning electron microscopic observations. The vessels within duct walls were mainly capillaries, while those around the duct walls were composed of capillaries and venules. A majority of vessels was positive for factor VIII-related antigen and Ulex europaeus lectin I. Scanning electron microscopy of hepatic arterial and biliary casts revealed that bile ducts were surrounded by the vascular plexus derived from hepatic arterial branches, and serial section observations in addition disclosed the vessels connecting the peribiliary plexus with portal venous branches ('internal roots'). The peribiliary vascular plexus was increased considerably in livers with portal hypertension, especially idiopathic portal hypertension, extrahepatic portal venous obstruction and hepatocellular carcinoma with portal venous tumor thrombi. Internal roots were also frequently found in the livers with portal hypertension. These results suggest that altered intrahepatic hemodynamics in portal hypertensive conditions involves the peribiliary vascular plexus, resulting in an increase of the number and frequent occurrence of 'internal roots', these vessels probably operating as intrahepatic collaterals.