Biliary tract anatomy and its relationship with venous drainage.

Portal cavernoma develops as a bunch of hepatopetal collaterals in response to portomesenteric venous obstruction and induces morphological changes in the biliary ducts, referred to as portal cavernoma cholangiopathy. This article briefly reviews the available literature on the vascular supply of the biliary tract in the light of biliary changes induced by portal cavernoma. Literature pertaining to venous drainage of the biliary tract is scanty whereas more attention was focused on the arterial supply probably because of its significant surgical implications in liver transplantation and development of ischemic changes and strictures in the bile duct due to vasculobiliary injuries. Since the general pattern of arterial supply and venous drainage of the bile ducts is quite similar, the arterial supply of the biliary tract is also reviewed. Fine branches from the posterior superior pancreaticoduodenal, retroportal, gastroduodenal, hepatic and cystic arteries form two plexuses to supply the bile ducts. The paracholedochal plexus, as right and left marginal arteries, run along the margins of the bile duct and the reticular epicholedochal plexus lie on the surface. The retropancreatic, hilar and intrahepatic parts of biliary tract has copious supply, but the supraduodenal bile duct has the poorest vascularization and hence susceptible to ischemic changes. Two venous plexuses drain the biliary tract. A fine reticular epicholedochal venous plexus on the wall of the bile duct drains into the paracholedochal venous plexus (also called as marginal veins or parabiliary venous system) which in turn is connected to the posterior superior pancreaticoduodenal vein, gastrocolic trunk, right gastric vein, superior mesenteric vein inferiorly and intrahepatic portal vein branches superiorly. These pericholedochal venous plexuses constitute the porto-portal collaterals and dilate in portomesenteric venous obstruction forming the portal cavernoma.