| Common bile duct | |
|---|---|
 Diagram of the biliary tree showing the common bile duct | |
| Details | |
| Part of | Biliary tract |
| Identifiers | |
| Latin | ductus choledochus,[1] ductus biliaris[1] |
| Acronym | CBD[2] |
| MeSH | D003135 |
| TA98 | A05.8.02.013 |
| TA2 | 3103 |
| FMA | 14667 |
| Anatomical terminology | |
Thecommon bile duct (alsobile duct) is a part of thebiliary tract.[1][4] It is formed by the union of thecommon hepatic duct andcystic duct. It ends by uniting with thepancreatic duct to form theampulla of Vater (hepatopancreatic ampulla). Itssphincter thesphincter of Oddi, enables the regulation of bile flow.
The bile duct is some 6–8 cm long, and normally up to 8 mm in diameter.[4]
Its proximal supraduodenal part is situated within the free edge of thelesser omentum. Its middle retroduodenal part is oriented inferiorly and right-ward, and is situated posterior to the first part of the duodenum, and anterior to the inferior vena cava. Its distal paraduodenal part is oriented still more right-ward, is accommodated by a groove upon (sometimes a channel within) the posterior aspect of the head of the pancreas, and is situated anterior to the rightrenal vein.[4]
The bile duct terminates by uniting with thepancreatic duct (at an angle of about 60°) to form theAmpulla of Vater (hepatopancreatic ampulla).[4]
The distal extremity of the bile duct invariably features its ownsphincter (the pancreatic duct and the Ampulla of Vater usually possess sphincters of their own to allow the flow of pancreatic juice to be regulated independently, however, these two can be absent).[4]
Several problems can arise within the common bile duct, usually related to its obstruction. Opinions vary slightly on the maximum calibre of a normal CBD, but 6 mm is one accepted upper limit of normal[5] with a further 1mm diameter allowed for each decade over 60 years.
It normally gets slightly dilated aftercholecystectomy, with upper limit (95%prediction interval) being about 10 mm after a few months.[6]
Onabdominal ultrasonography, the common bile duct is most readily seen in theporta hepatis (where the CBD lies anterior to theportal vein andhepatic artery). The absence ofDoppler signal distinguishes it from theportal vein andhepatic artery.
Tumours in the head of the pancreasmay come to obstruct the distal bile duct.[4]
If obstructed by agallstone, a condition calledcholedocholithiasis can result.[7] In this obstructed state, the duct is especially vulnerable to an infection calledascending cholangitis. One form of treatment is acholecystenterostomy. Rare deformities of the common bile duct are cystic dilations (4 cm), choledochoceles (cystic dilation of the ampulla of Vater (3–8 cm)), andbiliary atresia.
Obstruction of the common bile duct and relatedjaundice has been documented since at least since the time ofErasistratus.[8]
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