Coledoco Conduit: What is it? Clinical Significance, Spontaneous Perforation and Cystic Dilation

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 ducts 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 open, stored and concentrated bile leaves the duodenum.

This conduction of bile is the main 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 duct 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 main pancreatic duct.

The choledochal duct and the main pancreatic duct unite before emptying their contents into the duodenum through the papillary orifice at the end of the duodenal papilla, a small, nipple-like structure that extends into the duodenum.

The hormone’s cholecystokinin, when stimulated by a fatty meal, 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 it is blocked by a gallstone, a condition called choledocholithiasis may occur. In this obstructed state, the duct is especially vulnerable to an infection called ascending cholangitis.

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.

The use of grasping forceps or biopsy should be avoided if possible because these instruments can damage the bile duct.

Blockage of the choledochal duct and related jaundice has been documented since at least the time of 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 as a result of infection and bile stasis (usually cholesterol stones), or may occur in a post-cholecystectomy patient (usually brown stones).

While stones can often pass through the choledochal duct into the duodenum, some stones may be too large to pass through the choledochal duct and may cause an obstruction.

A risk factor for this is 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, which is usually sterile.

Ultrasonography confirms ascites, which is 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 repair of perforation usually provide effective treatment. Cholecystojejunostomy may be necessary 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, although pancreatic juices have also been refluxed into the bile duct as a result of 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 up to 90% of cases. Microscopically, the cyst wall of the common bile duct is fibrotic and is inflamed in a variable 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.

Complications include biliary obstruction, cholangitis, cirrhosis, and cholangiocarcinoma. Complete surgical excision is the treatment of choice.