1. THE INTRAHEPATIC BILIARY TREE

Abstract

This chapter discusses the intrahepatic biliary tree. The biliary tree is the conduit between the hepatocellular parenchyma of the liver and the gut. Loss of patency of this conduit is incompatible with life, in the neonate or at any other time in life. The volume of the human adult intrahepatic biliary tree is estimated to be between 14–24 cm 3 , with an internal surface area of between 330–575 cm 2 . Maturation of the intrahepatic biliary tree constitutes an elegant mechanism for maintaining patency of the biliary passages, whilst undergoing major structural reorganization throughout the second and third trimesters and into the post-partum period. As bile begins to flow around the 12th week of gestation, the physiologic events of bile formation can proceed without structural impediment. Throughout post-natal life, secretion of bile by hepatocytes is accompanied by secretion of a bicarbonate-rich fluid by the cholangiocytes lining the biliary tree, with cholangiocyte secretiono constituting up to 40% of bile volume. The final architecture of the intrahepatic biliary tree consists of: hemicircular canals of Hering linking the bile canaliculi between hepatocytes to the smallest complete channels of the biliary tree—bile ductules. The bile ductules serve as tethers between the hepatic parenchyma and the terminal twigs of the biliary tree, interlobular bile ducts. Interlobular bile ducts drain into septal bile ducts, and thence, into area bile ducts, segmental bile ducts, and finally, the main hepatic ducts.