Surgical anatomy of the left hepatic duct: a simplified classification system for anatomical variants

The existing knowledge on anatomy of the left hepatic duct (LHD) is limited. This study aims to describe the surgical anatomy of LHD and its variations with special emphasis on its segmental branching pattern.

Forty fresh cadaveric liver dissections were performed. After removing the hepatic artery and portal vein branches, the LHD was opened longitudinally, from the origin of the main hepatic duct in the upper biliary confluent to the left, thus letting discover the ostia of S2, S3 and S4 ducts, which were opened longitudinally as well. LHD characteristics, the number and situation of its segmental branches were recorded.

The LHD run posteriorly to the left portal vein in all the cases. The mean length of the LHD was 18.8 ± 8 mm. Depending on the anatomical disposition of the bile ducts, we identified 4 types of left biliary schemes. The S2 and S3 ducts form the left lateral lobe duct (LLLD), and then unite to 2 S4 ducts (type 1, 45%) or a single S4 duct (type 2, 37%), to form the LHD. In type 3 (12%), S2 duct joint a common S3-4 duct. In the last uncommonest type 4 (5%), LLLD is too short or inexistent, with S2-S3 ducts and S4 as well joining to the right from the umbilical fissure.

The present study comprehensively describes the surgical anatomy of the segmental branches of the LHD and proposes a simplified classification system for the different anatomical variants. Detailed knowledge of segmental anatomy of the LHD helps surgeons to identify the most appropriate transection plane while performing extended liver resections or reduced-graft liver transplantation.