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 biliary tree (see below) is the whole network of various sized ducts branching through the liver.
The path is as follows: Bile canaliculi → Canals of Hering → interlobular bile ducts → intrahepatic bile ducts → left and right hepatic ducts merge to form → common hepatic duct exits liver and joins → cystic duct (from gall bladder) forming → common bile duct → joins with pancreatic duct → forming ampulla of Vater → enters duodenum
Common bile duct
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 into the part of the intestine called the duodenum via the
ampulla of Vater.
Pathology
Blockage of the bile duct by a
cancer, gallstones, or scarring from injury prevents the bile from being transported to the intestine and the active ingredient in the bile (
bilirubin) instead accumulates in the
blood. This condition results in
jaundice, where the
skin and
eyes become yellow from the bilirubin in the blood. This condition also causes severe itchiness from the bilirubin deposited in the tissues. In certain types of jaundice, the urine will be noticeably darker, and the stools will be much paler than usual. This is caused by the bilirubin all going to the bloodstream and being filtered into the urine by the kidneys, instead of some being lost in the stools through the ampulla of Vater.
Jaundice is commonly caused by conditions such as pancreatic cancer, which causes blockage of the bile duct passing through the cancerous portion of the pancreas; cholangiocarcinoma, cancer of the bile ducts; blockage by a stone in patients with gallstones; and from scarring after injury to the bile duct during gallbladder removal.
Sensation
Inflation of a balloon in the bile duct causes through the
vagus nerve, activation of the
brain stem and the
insular cortex,
prefrontal cortex, and
somatosensory cortex.
==Drainage==
Biliary drainage is performed with a tube or catheter (called a biliary drain, biliary stent or biliary catheter). It can be used to relieve a blockage in the bile duct, either permanently or as a temporary solution before definite treatment such as surgery. The drain can be placed percutaneously through the liver, with the procedure then being called percutaneous transhepatic biliary drainage (PTBD). This can additionally be performed as part of a percutaneous transhepatic cholangiography, then a form of interventional radiology. A biliary drain can also be used to take bile samples for diagnostic workup or disease monitoring, as well as providing a route of administration for medical substances.
In infants with biliary atresia, hepatoportoenterostomy is an alternative method of providing bile drainage.
References
Additional images
External links
The Cholangiocarcinoma Foundation
The Johns Hopkins Gall Bladder & Bile Duct Cancer Web page
www.thebile.com
Measuring bile duct hyperplasia in toxicology
Category:Digestive system
Category:Hepatology
