Biliary tree anatomy

Last revised by Raymond Chieng on 19 Feb 2023

A branching ductal system that collects bile from the hepatic parenchyma and transports it to the duodenum constitutes the biliary tree.

Gross anatomy

By convention the biliary tree is divided into intra- and extra-hepatic bile ducts 1. There is significant variation in the biliary tree with the classical description below thought to be present in ~60% of the population 2.

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 5:

  • 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 form the right hepatic duct (RHD)

  • segmental bile ducts from 2, 3, 4a and 4b 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 (caudate lobe) drain into the angle of this 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 3

Extrahepatic bile ducts

The common hepatic duct is joined by the cystic duct (from the gallbladder) to form the common bile duct 6.

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 6

Variant anatomy

Intrahepatic bile ducts

Variant anatomy is quite common 2:

  • right posterior sectoral duct draining into LHD ~15% (range 13-19%)

  • right anterior sectoral duct draining into LHD ~6%4

  • right posterior sectoral duct draining into anterior (not posterior) aspect of right anterior sectoral duct ~12%

  • "triple confluence": union of RPSD, RASD and LHD to form CHD ~11%

  • aberrant hepatic duct (typically RPSD draining into CHD) ~6%

  • low insertion of RHD into CHD ~2%4

  • accessory hepatic ducts ~2%

  • subvesical bile ducts

Extrahepatic bile ducts

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Cases and figures

  • Figure 1
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  • Figure 2: cystic duct anatomy
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  • Figure 3: common duct anatomy
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  • Figure 4: intrahepatic duct anatomy
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  • Case 1: normal anatomy in a CT intravenous cholangiogram
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  • Case 2: variant "triple confluence" on MRCP
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  • Case 3: variant, triple confluence
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