Bile Duct/Common Bile Duct (CBD)

The Common Bile Duct is a small tube-like gastrointestinal tract in the organisms that have a gall bladder.

Foundation

The foundation of the bile duct is near the porta hepatis, by the joining of cystic and common hepatic ducts. It measures typically about 7.5 cm (3 inches) in length and about 6 millimeters in diameter.

Parts

It’s divided into 4 parts:

• Supraduodenal part.
• Retroduodenal part.
• Infraduodenal (or pancreatic) part.
• Intraduodenal part

Supraduodenal Part

It’s about 2.5 cm long and descends in the right free margin of the lesser omentum to the right of the hepatic artery appropriate and anterior to the portal vein.

Retroduodenal Part

It descends behind the initial part of the duodenum with the gastroduodenal artery on its left and IVC on its posterior aspect.

Infraduodenal (Pancreatic) Part

It runs in the groove on the upper and lateral parts of the posterior outermost layer of the pancreas and is occasionally totally embedded in the pancreatic tissue. Here it is located in front of the IVC from which it’s divided by a thin layer of pancreatic tissue.

It’s escorted on its left side by the gastroduodenal artery, which provides origin to the superior pancreaticoduodenal artery.

The superior pancreaticoduodenal artery crosses the bile duct either anteriorly or posteriorly. Medically it’s a source of hemorrhage in the vulnerability of infraduodenal part of the bile duct. Near the middle 2nd part of the duodenum, it comes in touch together with the pancreatic duct.

Intraduodenal (or Intramural) Part

It enters the posteromedial surface of the descending (2nd) part of the duodenum a little below to its middle. The main pancreatic duct also enters the wall of the duodenum at thesame site. Both ducts run obliquely in the wall of the duodenum and link to create a growth, the hepatopancreatic ampulla (or ampulla of Vater), which bulges the mucous membrane of duodenum inward creating the major duodenal papilla. The distal constricted end of the ampulla opens on the peak of the major duodenal papilla 8-10 cm distal to the pylorus.

Sphincters around the terminal parts of Bile and Pancreatic ducts and Ampulla

The intramural parts (terminal parts) of bile and pancreatic ducts in addition to ampulla are surrounded by smooth muscle sphincters. The sphincter around the bile duct is known as sphincter choledochus (of Boyden), the sphincter around the pancreatic duct is referred to as sphincter pancreaticus, and the sphincter around the ampulla is referred to as sphincter ampullae (of Oddi). The 3 sphincters are separate of duodenal musculature. The sphincters stay closed until the gastric contents goes into the duodenum, sparking its mucosa to release a hormone referred to as cholecystokinin. This hormone in addition to causing contraction of the gallbladder loosens these sphincters letting bile and pancreatic secretions to goes into the duodenum.

Arterial Supply of the Bile Duct/Common Bile Duct

The upper part of bile duct is provided by a twig from the descending branch of cystic artery while its lower part is provided by the ascending branch of the superior pancreaticoduodenal artery.

Clinical Significance

Arterial supply of the common bile duct (CBD) is medically significant because if the anastomosis between the superior and inferior pancreaticoduodenal arteries is lousy, the ligation of superior pancreaticoduodenal artery during surgery can result in gangrene of the common bile duct.