biliary tree anatomy

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Various channels that collect bile from the hepatic parenchyma and transport it to the duodenum constitute the biliary tree.

Gross anatomy

By convention the biliary tree is divided into intra- and extra-hepatic bile ducts . There is significant variation in the biliary tree with the classical description below thought to be present in ~60% of the population .

Intrahepatic bile ducts

Bile canaliculi unite to form segmental bile ducts which drain each liver segment. The segmental ducts then combine to form sectoral ducts with the following pattern :

segments 6 and 7: right posterior sectoral duct (RPSD), coursing more horizontally
segments 5 and 8: right anterior sectoral duct (RASD), coursing more vertically
right posterior and anterior sectoral ducts unite to from the right hepatic duct (RHD)
segmental bile ducts from 2-to-4 unite to form the left hepatic duct (LHD)

The left and right hepatic ducts unite to form the common hepatic duct (CHD). Bile duct(s) from segment 1 drain into the angle of their union.

The ducts of the left hepatic lobe are more anterior than those of the right lobe; it is important particularly when contrast cholangiogram is performed because contrast may not opacify non-dependent ducts .

Extrahepatic bile ducts

The common hepatic duct is joined by the cystic duct (from the gallbladder) to form the common bile duct.

The common bile duct travels initially in the free edge of the lesser omentum, then courses posteriorly to the duodenum and pancreas to unite with the main pancreatic duct to form the ampulla of Vater, which drains at the major duodenal papillae on the medial wall of the D2 segment of the duodenum.