A bile duct is any of a number of long tube-like structures that carry bile.

Bile, required for the digestion of food, is excreted by the liver into passages that carry bile toward the hepatic duct , which joins with the cystic duct (carrying bile to and from the gallbladder) to form the common bile duct, which opens into the intestine.

The top half of the common bile duct is associated with the liver, while the bottom half of the common bile duct is associated with the pancreas, through which it passes on its way to the intestine. It opens in the part of the intestine called the duodenum into a structure called the ampulla of Vater.

Blockage of the bile duct by a cancer or scarring from injury prevents the bile from being transported to the intestine and the bile accumulates in the blood. This condition is called jaundice and the skin and eyes become yellow from the accumulated bile in the blood. This condition also causes severe itchiness.

Jaundice is commonly caused by conditions such as pancreatic cancer caused by blockage of the bile duct passing through the cancerous portion of the pancreas, cholangiocarcinoma, blockage by a stone in patients with gallstones and from scarring after injury to the bile duct during gallbladder removal.