Bile duct confluence: anatomic variations and its classification.

Accurate knowledge of the anatomy of the bile ducts is critical for successfully hepato-biliary surgery. We describe the anatomical variations of the confluence of the bile ducts, their branches patterns, frequency and classification. From 1996 to 2011, we have collected data of the bile duct confluence. 2,032 and 1,014 anatomical variations of right and left bile ducts, respectively, were reviewed and classified according to the branching pattern. The frequencies of each type of the right hepatic duct (RHD) were as follows: Type A1-1,247 (61.3%); Type A2-296 (14.5%); Type A3-272 (13.3%); Type A4-124 (6.1%); Type A5-21 (1%) and others-72 (3.5%) and, for the left hepatic duct (LHD) was as follows: Type B1-773 (76.2%); Type B2-153 (15%); Type B3-38 (3.7%); Type B4-9 (0.8%); Type B5-29 (2.8%) and others-12 (1.1%). Atypical branching patterns of both the right and left hepatic ducts were found in 14 and 8%, respectively. The two most common variations of the RHD were right anterior and posterior hepatic ducts join together to form the RHD and trifurcation where the RHD is absent and right anterior and posterior hepatic ducts join directly to the confluence with the LHD to form the common hepatic duct. The two most common variations in the LHD were segment IV drainage to the left and right hepatic ducts.