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Sometimes abbreviated as common bile duct (CBC), it is a conduit in the gastrointestinal tract of organisms that has the gallbladder.
It is formed by the union of the hepatic duct and the cystic duct of the gallbladder.
The choledochal duct is a small tube-shaped structure; its physiological function is to transport bile from the gallbladder and empty it in the upper part of the small intestine (the duodenum). The choledochal duct is part of the biliary system.
Subsequently, the pancreatic duct is joined to form the ampulla of Vater. There, the two vents are surrounded by the muscular sphincter of Oddi.
When the sphincter of Oddi is closed, newly synthesized bile from the liver is stored in the gallbladder. When it is available, reserved and concentrated bitterness leaves the duodenum.
This conduction of bile is the primary function of the choledochal duct. The bile ducts carry bile, a liquid that the liver produces to help break down food.
A group of small bile ducts called the biliary tree in the liver empty the bile into the larger choledochal duct. Between meals, the choledochal vent closes, and the bile collects a pear-shaped sack from the liver in the gallbladder.
The pancreatic ducts carry pancreatic juice, a fluid that the pancreas produces to help break down food. A group of small pancreatic ducts in the pancreas empties into the ventral pancreatic duct.
The choledochal duct and the ventral pancreatic duct unite before emptying their contents into the duodenum through the papillary orifice at the end of the duodenal papilla. This small, nipple-like structure extends into the duodenum.
When stimulated by a fatty meal, the hormone cholecystokinin promotes the secretion of bile by increasing the production of hepatic bile, contraction of the gallbladder, and relaxation of the sphincter of Oddi.
Clinical significance
Several problems may arise within the choledochal canal. A diameter of more than 8mm is considered an abnormal dilation and is a sign of cholestasis.
If a gallstone blocks it, choledocholithiasis may occur. The duct is especially vulnerable to ascending cholangitis infection in this obstructed state.
The very rare deformities of the choledochal duct are cystic dilatations (4cm), choledochoceles (cystic dilatation of the Vater’s ampulla (3-8cm)), and biliary atresia.
Grasping forceps or biopsies should be avoided because these instruments can damage the bile duct.
Blockage of the choledochal duct and related jaundice has been documented since Erasistratus.
Stone of the coledoco conduit
The stone of the choledochal duct, also known as choledocholithiasis, is the presence of gallstones in the choledochal duct (therefore, choledocholithiasis). This condition causes jaundice and damage to the liver cells. The treatment is by cholecystectomy and endoscopic retrograde cholangiopancreatography.
Choledochal duct stones may descend from the gallbladder or arise again in a dilated, tortuous choledochal duct due to infection and bile stasis (usually cholesterol stones) or may occur in a post-cholecystectomy patient (usually brown rocks).
While stones can often pass through the choledochal duct into the duodenum, some rocks may be too large to pass through the choledochal duct and may cause an obstruction.
A risk factor for this is the duodenal diverticulum.
Choledochal duct stones rarely occur in infants and children. Symptomatic choledocholithiasis, usually associated with cholelithiasis, is the predominant indication of endoscopic retrograde cholangiopancreatography in children.
Spontaneous drilling
Spontaneous perforation of the choledochal duct is a rare cholestatic disorder of childhood. Perforation usually occurs at the junction of cystic and common ducts.
The cause is unknown, but congenital or acquired weakness at the site has been proposed, obstruction at the distal end of the choledochal duct due to stenosis or thick bile.
Babies present with little weight gain, jaundice, acholic stools, dark urine, and ascites. Progressive abdominal distension usually occurs due to ascites with biliary staining of umbilical and inguinal hernias.
The hyperbilirubinemia conjugate mild to moderate with minimal elevation of serum aminotransferase levels is typical. The abdominal paracentesis reveals clear ascitic fluid stained with bile, usually sterile.
Ultrasonography confirms ascites, which are sometimes loculated in the right upper quadrant. There is no biliary dilation. The hepatobiliary scintigraphy is diagnostic and shows the isotope-free accumulation within the peritoneal cavity.
Surgical cholangiography is necessary to demonstrate the site of the perforation. In laparotomy, drainage of bilious ascites and perforation repair usually provide effective treatment. Cholecystojejunostomy may be required in some babies with choledochal duct stenosis.
Choledochal duct cyst
Cystic dilation of the choledochal duct, or common bile duct cyst, is generally considered a congenital disorder. However, pancreatic juices have also been refluxed into the bile duct due to an abnormal pancreaticobiliary junction.
Patients may present early in life with cholestatic jaundice due to biliary obstruction or as adults with intermittent epigastric pain and symptoms of cholangitis such as fever and jaundice. Classification is based on anatomical location and range.
Type I, a segmental dilation of the choledochal duct, represents 90% of cases. Microscopically, the common bile duct cyst wall is fibrotic and inflamed in an inconsistent manner.
The biliary epithelial lining is often denuded. Metastasis of goblet cells and squamous metaplasia have been described, and dysplastic changes can be observed in samples from older patients.
