General anatomy
The bile duct drains bile from the liver into the duodenum. This way, bile aids in the digestion of lipids in the food. The intrahepatic biliary tract comprises the right and left hepatic duct (ductus hepaticus dexter et sinister) which descend from the liver. Their union forms the common hepatic duct (ductus hepaticus communis). Along its course to the duodenum it is joined by the cystic duct (ductus cysticus) from the gallbladder (vesica biliaris). The union of the common hepatic duct and the cystic duct forms the common bile duct (ductus choledochus) which drains into the duodenum. The major duodenal papilla (papilla of Vater) is a sphincter muscle controlling the bile flow from the common bile duct into the duodenum.
Specific anatomy
In 75% of cases, the sole arterial blood supply for the gallbladder is a single cystic artery, arising from the right hepatic artery which courses posterior to the right hepatic duct (see figure above). In all other cases, the cystic artery arises from other branches of the hepatic arteries, and even the gastroduodenal artery, and courses anterior to the common hepatic duct, or the gallbladder is supplied by several arterial branches. Many times, hemorrhage obscuring the view of the surgical field can be controlled by compressing the hepatic artery within the hepatoduodenal ligament or by clamping of the hepatic pedicle (Pringle maneuver). Persistent bleeding may be indicative of an accessory hepatic artery arising from the superior mesenteric artery!
While anomalies of the cystic duct are less common than vascular variants, their impact in terms of injuries to the common bile duct is more severe. The cystic duct may join the biliary tree at any point, including the duodenal papilla. Therefore, the length of the cystic duct may vary significantly, from being very short to complete absence, and it may spiral anterior or posterior to the common hepatic duct or may even share a common wall (duplicated common bile duct). In addition, accessory bile ducts from the liver may drain into the cystic duct, gallbladder or right hepatic duct. Whenever the anatomy of the cystic duct is in doubt, there is always the option of opening the gallbladder and probing the cystic duct from within the gallbladder. Option: In case of doubt perform intraoperative cholangiography!
Injuries of the common bile duct are mostly due to anatomic anomalies or disease-induced tissue changes. Excessive traction on the cystic duct may result in knuckling of the common duct and applying the forceps too low, thereby catching and ligating part of the edge of the common duct. This will result in stenosis or even complete transection of the common duct.