Background: Hepatobiliary and pancreatic system embryologically developed through a complex process of cell budding from ventral part of the distal foregut and fusion. Hepatobiliary system probably has the most associated anatomical variations in the body and they are direct reflection of the complexity of the embryological development
Methodology: English language literature review on the anatomical variations of the extra-hepatic biliary system and the summative prevalence of the major relevant anatomical anomalies is presented for the benefit of the practicing and aspiring surgeons.
Results: Extrahepatic biliary system has the highest proportion of anatomical variations of any site in the body accounting for 8%-14% in autopsy series and 47.2% in biliary tract operations. Hepatic ducts unite to become common hepatic duct (CHD) outside the liver in about 96% and intrahepatic in 4-5% of cases. Cystic duct variations are the most common with significant implication for cholecystectomy. Its length, course and the pattern of joining the CHD forming the common bile duct (CBD) show significant variations from short straight to tortuous course, low to high and lateral to medial insertion into the CHD. True absent cystic duct is rare (0.01-0.25%). Its entry into CHD varies from the right, posterior, left and running parallel with a low insertion in 10-17%, 41%, 35% and 7-9% of cases respectively. Abnormal insertion into either of the hepatic duct or directly into the duodenum has been rarely reported. Reported incidence of accessory hepatic duct of various types is 1-30%. Duplicated or congenital absence of either the gallbladder or CBD is a very rare event. The incidence of absent gallbladder is reported to be 0.0013-0.075% while CBD duplication has been reported in only 24 cases.
Conclusion: Anatomical variations of the cystic and accessory hepatic ducts have the most significant implications for biliary tract injury and bile leak following cholecystectomy