Applied Radiology

Diagnosis

Choledochal cyst (type 1)

Findings

There is cystic dilatation of the entire length of the common bile duct. The cystic duct is seen draining into the choledochal cyst. No solid tissue is seen within the cyst. No calculi are identified. There is no intrahepatic or pancreatic ductal dilatation.

Discussion

Choledochal cysts are congenital cystic anomalies of the bile ducts. Although the exact etiology is uncertain, a common theory is that they arise in patients with an anomalous pancreaticobiliary junction resulting in a long common channel. These patients are more likely to have reflux of pancreatic secretions, which may weaken the wall of the common bile duct.

Ultrasound may be used in the initial evaluation. Magnetic resonance cholangiopancreatography (MRCP) or endoscopic retrograde cholangiopancreatography (ERCP) is used to further delineate biliary anatomy and to exclude obstructing lesion.

The widely used classification system for choledochal cysts is the Todani classification. Type 1 cysts, the most common, are confined to the extrahepatic bile duct. A true diverticulum of the common bile duct is referred to as a Type 2 cyst. Choledocholceles, confined to the extrahepatic duct within the duodenal wall, are classified as Type 3 cysts. Type 4 cysts are similar to Type 1, but they are accompanied by intrahepatic ductal dilatation. Lastly, in patients with Type 5 cysts, also referred to as Caroli’s disease, there is dilatation of intrahepatic ducts only.

The presentation of choledochal cysts is variable. Most patients present before the age of 10. They are 3 to 4 times more common in female patients. Abdominal mass, pain, and jaundice is the classic presenting triad; however, the entire triad is not frequently seen clinically.

Treatment of choledochal cysts involves complete surgical excision. Possible complications of choledochal cysts include cholangitis, calculi, and an increased risk of carcinoma, either within the choledochal cyst wall or in the remaining biliary tree following excision.

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4. Todani T, Watanabe Y, Narusue M, et al. Congenital bile duct cysts: Classification, operative procedures, and review of thirty-seven cases including cancer arising from choledochal cyst. Am J Surg. 1977;134:263-269.