Variant anatomy of the extrahepatic biliary system and its blood supply among black Kenyans

Abstract

Background: Anatomical variations of the human body including the extra hepatic biliary system exist across various individuals. Understanding the variant anatomy of the extrahepatic biliary system and its blood supply should aid surgeons in avoiding iatrogenic injuries. This is important in resource limited settings where it is not possible to perform adequate radiological investigations of the hepatobiliary system prior to surgery. Local studies have only focused on cystic artery variations; however, this study aims to assess variations in both the extrahepatic biliary system and its blood supply. Objective: The study described the anatomic variation of the extrahepatic biliary system and its blood supply among Kenyans. Methods: This was a cross-sectional study conducted at Moi University‟s Anatomy Laboratories among 42 adult cadaveric specimens. Specimen dissections were conducted as per the fifteenth edition of Cunningham‟s manual of Practical Anatomy. The variant anatomy data collected were filled in a structured data collection form, analyzed and presented using descriptive statistics. Study Findings: Of the 42 cadavers sampled, 62% (n=26) were male while 38% (n=16) were female. All the cadavers had a gall bladder being drained by the cystic duct. The length of the cystic duct ranged between 7mm to 35 mm with a median value of 17mm, and it joined the common hepatic duct to form the common bile duct in 98% (n=41) of all the cadavers sampled. This confluence was to the left in 7.1% (n=3), right 42.9% (n=18), anteriorly in 14.3% (n=6) and posteriorly 35.7% (n=14). A single cadaver (2%) had the cystic duct drain into the right hepatic duct. Two thirds (66.7%; n=28) of the cadavers sampled had the confluence of the right and the left hepatic duct outside the liver. There were no cholecystohepatic ducts in this study. Of the study subjects, 71.4% (n=30) had a normal pattern of the extrahepatic supply (Type 1). The normal origin of the right hepatic artery from the proper hepatic artery or common hepatic artery was seen in 81% (n=34) a while 19% (n=8) had an aberrant origin (Type 3 and 4) from the superior mesenteric artery. The course of the right hepatic artery was anterior to common hepatic duct and common bile duct in 26.2% (n=11) of all the cadavers. Less than half of the cadavers 43% (n=18) had a caterpillar hump of the right hepatic artery occupy the Calot‟s triangle. All cystic arteries were within the Calot‟s triangle; however, 45.2% (n=19) of the cystic arteries arose from the right hepatic artery outside the Calot‟s triangle anterior to the common hepatic duct. Conclusion: The study determined the existence of surgically important variant anatomy of the extrahepatic biliary system and its blood supply among black Kenyans. The caterpillar hump of the right hepatic artery occupying the Calot‟s triangle was the most frequent variation. Recommendation: There is need for greater appreciation of the extrahepatic biliary system variant anatomy by both surgeons and radiologists so as to decrease morbidity and improve on surgical outcomes.