common bile duct
The common bile duct (CBD), which is sometimes simply known as the bile duct, is formed by the union of the cystic duct and common hepatic duct (CHD).
Terminology
On ultrasound imaging, it is not always possible to confidently see where the cystic duct enters the common hepatic duct to form the common bile duct. Therefore it is common practice to use the term common duct (CD) as a term conflating the common hepatic and common bile ducts.
Gross anatomy
The CBD is approximately 8 cm long and usually <6 mm wide in internal diameter but this can be dependent on a number of factors including age and prior cholecystectomy. It joins the pancreatic duct at the ampulla of Vater, which drains into the second part of the duodenum through the major duodenal papilla.
Arterial Supply
The common bile duct is supplied by a network of arteries from several sources:
- from above: right hepatic artery and cystic artery
- from below: posterior superior pancreaticoduodenal artery, retroduodenal artery, and retroportal artery
Variant anatomy
There are four main relationships of the CBD with the pancreatic head :
- partially covered posteriorly (most common: ~50%)
- completely covered
- completely uncovered
- CBD may pass laterally to the pancreatic head (least common)