What is a bile duct cyst?
Bile ducts cysts, also known as choledochal cysts, are abnormal dilatations of the bile ducts especially the common bile duct. It is a congential anomaly, meaning that it is present from birth, and up to 20% of cases can remain asymptomatic until adulthood. These abnormal dilatations may involve part of the bile duct or the entire biliary tree, extending to the surrounding bile passages like those within the liver (intrahepatic biliary tree). Choledochal cysts are not a common condition and produce non-specific symptoms of liver and biliary disease in the early years of life.
The bile ducts are narrow passages that carry bile from the liver to the lumen of the duodenum. As bile flows through the canaliculi of the liver, it collects into the hepatic ducts and drain into the bile duct. Here it may enter the gallbladder where it is stored and released when needed. The bile duct is also joined by the pancreatic duct, which carries the pancreatic digestive enzymes into the duodenum. Read more on bile duct anatomy.
Types of Bile Duct Cysts
Simply, a choledochal cyst is an outpouching of the bile duct. It may vary in shape and distribution and therefore can be divided into five types of cysts. Most bile duct cysts are type I cysts.
- Type I cysts are saccular or fusiform dilatations involving part of or the entire bile duct that does not lie within the liver (extrahepatic). A saccular or fusiform dilatation means that the bile duct is bulging on all sides making it appear enlarged. Saccular cysts are as the name describes and the normally narrow bile duct becomes like a sac. Fusiform cysts are bulging in the middle but taper on either end. There are various sub-types including :
- Type IA which is saccular and involves most or all of the biliary tree.
- Type IB which is also saccular but only involves a limited portion of the biliary tree.
- Type IC which is more fusiform and involves most if not all of the biliary tree.
- Type II is an isolated sac (diverticulum) protruding from the common bile duct. Its walls may be continuous with the duct or it may be attached to it by a narrow stalk.
- Type III cysts arise from the intraduodenal portion of the bile duct, which is the part that extends into the duodenum of the small intestine. It is also known as a choledochocele and is a risk factor for bile duct stones, stenosis, strictures and obstruction as discussed under bile duct blockage.
- Type IV are multiple dilatations of the biliary tree. With type IVA, this may involve both the intrahepatic (within the liver) and extrahepatic (lying out of the liver) bile ducts. In type IVB, the multiple dilatations are isolated to the extrahepatic biliary tree only.
- Type V involves multiple dilatations of the intrahepatic biliary tree and is known as Caroli disease.
Signs and Symptoms of Bile Duct Cysts
The clinical presentation may vary with age and it is possible for a person with bile duct cysts to only show symptoms in adulthood. Jaundice and right upper abdominal pain are the more common symptoms.
Infants are unable to express abdominal pain so other symptoms that may be indicative of abdominal discomfort should be monitored like inconsolable crying, curling up in a ball and crying when the abdomen is touched or with tight clothing. Jaundice with pale stools and hepatomegaly (enlarged liver) may be seen in infants. With older children, the jaundice and pain may be associated with repeated episodes of bile duct obstruction and pancreatitis. The pain may close resemble gallstone pain and is associated with a mass in the right upper quadrant of the abdomen. In adults, the presentation may be more complex with jaundice and upper abdominal pain seen with conditions like cholangitis and complications like recurrent pancreatitis, cirrhosis and liver abscesses.