What is a choledochal cyst?
This an inborn abnormality of the bile duct that causes it to enlarge. These cysts can be intrahepatic (occur in the part of the duct inside the liver) or extrahepatic (part of the bile duct outside the liver). The different types of choledochal cysts depend on the location and type of enlargement.

• Type 1 – the most common type, making up about half of all choledochal cysts. It is a cystic dilation of the bile duct.
• Type 2 – an abnormal pouch or sac opening from the duct.
• Type 3 – located within the wall of the duodenum (first part of the small intestine).
• Type 4 – cystic dilations of both the intrahepatic and extrahepatic biliary tracts.
• Type 5 – this is the clustering of cysts, also known as Caroli’s disease.

SIGNS AND SYMPTOMS
The patient suffers jaundice due to a lack of drainage of bile from the abnormal bile duct. The poor drainage causes infections in the bile duct and some patients develop repeated inflammation of the pancreas since the pancreatic duct may enter into the abnormal bile duct.

Most patients present the condition in infancy or early childhood but occasionally the first symptoms may be in the teenage years or in adulthood.

An ultrasound is used to diagnose choledochal cysts. It usually shows an abnormal bile duct.

An Endoscopic Retrograde Cholangio-Pancreatography (ERCP) is then used to show the abnormal enlargement of the bile duct.

ERCP is where an endoscope is passed through the mouth and stomach and into the upper part of the small intestine. A blue fluid is then pumped into the opening of the main bile duct, which will show up on X-ray.

Currently, the new multi-slice CT scan is increasingly the investigation of choice because it shows the anatomy in greater detail.

TREATMENT
The treatment of choice is surgery to remove the cyst. The abnormal segment of the bile duct is completely removed and the small intestine is then brought up to the bile duct and stitched to the normal bile duct so that bile secretions are routed back into the intestine.

Traditionally, the cyst with the abnormal diseased bile duct was often left behind and stitched to the small intestine to relieve the jaundice. However, leaving the cyst behind is no longer recommended since this can result in serious complications.

Called cyst-duodenostomy, the choledochal cyst, which was left in place, is joined to the duodenum. This method has since been stopped since patients treated this way often develop complications such as cholangitis and subsequent cirrhosis.

Another method that also leaves the cyst behind is the Roux-en-Y cyst-jejunostomy. It is the drainage of the cyst into a specially constructed intestinal arrangement for drainage of bile. This has worked for a few patients but there is the long-term risk of cancer as the cyst itself remains in place. This operation is also no longer performed.

According to experts, up to 70 per cent of patients in whom cyst is not removed needed follow up operations to remove the cyst later. Another major worry is that the patient may develop bile duct cancer in the wall of the cyst.

The procedure today is to completely remove the dilated duct system outside the liver and drain the bile duct as it leaves the liver into a loop of intestine designed to prevent backflow. The procedure can also be done using laparoscopic surgery in selected patients.

Associate Professor Pierce Chow, a senior consultant surgeon at the Singapore General Hospital, said this keyhole procedure is still experimental. There is the worry that malignancy may have already developed and increased abdominal pressure necessary for such operations may spread the cancer.

"The repeated inflammation of the bile duct means there is the danger of tearing the portal vein when removing the cyst. This is one reason why surgeons not specialized in liver surgery are generally reluctant to remove the cyst. Removing the cyst is laparascopically compounds the potential danger," he explains.