Choledochal cysts

There are different types of choledochal cysts. They are categorised by their size and where they are found. They affect the main trunk of the biliary tree, known as the common bile duct, causing it to become unusually enlarged. This is called cystic dilatation and probably occurs at time of birth. It leads to an abnormal junction between the common bile duct and the pancreatic duct (anomalous pancreatobiliary junction, or APBJ).

Usually by the age of two or three, but sometimes not until you have reached adulthood, the duct may form a cyst. This prevents the bile from reaching the intestine. Bile backs up into the liver, causing you to become jaundiced. Inflammation and weakening of the bile duct walls will follow.

In childhood this may lead to pancreatitis (inflammation of the pancreas), cholangitis and liver damage. The most worrying complication may be cholangiocarcinoma, a rare type of cancer that develops in cells lining the bile ducts in the liver.

Choledochal cysts are extremely rare. The condition affects females more than males and occurs more commonly in Southeast Asia, with more than 30% of reported cases occurring in Japan. The majority of choledochal cysts are seen in childhood, although some people may not show symptoms until they are adults.

Symptoms are jaundice, caused by the reduced amount of bile draining from the abnormal bile duct, and abdominal pains. Pain may be increased if the bile building up in the liver becomes infected. In some cases the cyst can be felt by the doctor when examining your abdomen.

The diagnosis of choledochal cysts is not difficult once the condition is suspected. Cysts can be confirmed by using imaging equipment such as ultrasound, MRI or magnetic resonance cholangiopancreatography (MRCP), endoscopic retrograde cholangio-pancreatography (ERCP) and CT.

MRI and MRCP studies are able to provide images of the cyst with more precise anatomic detail. MRCP is a specialised scan that is performed in the MRI machine that provides a picture of your biliary and pancreatic ducts. In this scan, the fl uid in your biliary ducts appears brighter while the surrounding organs and tissues will appear darker.

During an ERCP, the endoscope is passed into the duodenum and contrast medium is injected back up into the bile ducts. This can be visualised with X-ray screening allowing the gastroenterologist to see the outline of your biliary tree.

ERCP is an endoscopic procedure which, although invasive, is valuable in examining both your biliary and your pancreatic structures. It can identify problems with the biliary tree, cystic duct obstruction, gallstones, narrowings and tumours.

If the condition is not correctly diagnosed the blockage of bile may result in scarring (fi brosis) of your liver. Extensive scarring may lead to cirrhosis. If you are diagnosed as an adult, inflammation and damage to the bile ducts may have been occurring for many years.

Choledochal cysts are treated by surgical removal of the abnormal segment of the bile duct and reconstruction of the biliary tree so that bile travels back into the intestine. Leaving the diseased cyst in place is considered to increase the risk of developing cholangiocarcinoma.