A case of jaundice

Physical examination was unremarkable. Previous imaging of the abdomen in the form of ultrasound, CT and MR (Figs 1 and 2) were reported to show dilated bile ducts down to the level of the head of the pancreas with no obstructive cause identified. A previous percutaneous transhepatic cholangiography (PTC) had been unsuccessful. A liver biopsy had been performed and reported as normal. After reviewing the previous imaging, it was decided to perform a magnetic resonance cholangiography (MRCP) rather than ERCP and this confirmed the suspected diagnosis (Fig. 3).

Choledochal cysts are congenital cystic dilatations of the extrahepatic biliary tree. They may affect any part of the ductal system and are occasionally associated with dilation of the intrahepatic bile ducts. Todani classified these cysts into five groups with type 1 being the commonest, accounting for 80-90% of cases. There is a 3:1 female predominance. In adults, choledochal cyst classically presents with obstructive jaundice, abdominal pain and a right upper quadrant mass. However these clinical features are seen in less than 30% of children [1]. Thirty percent of patients present in the newborn period or infancy with mass or obstructive jaundice, 50% present by 10 years and 80% by young adulthood.

Pathogenesis is related to anomalous pancreaticobiliary duct union or abnormal duct union with resultant reflux of pancreatic juice into the extrahepatic bile ducts - the common channel theory [2]. Choledochal cysts are usually associated with abnormal liver histology with varying degrees of bile duct proliferation, cholestasis, parenchymal damage, inflammatory cell infiltration and pericentral fibrosis [3]. The patient's liver biopsy was normal in this case.

Complications of choledochal cysts include recurrent cholangitis, stone formation, cirrhosis, stricture, acute pancreatitis, portal hypertension and adenocarcinoma of the biliary tree, the incidence of which increases with age. Treatment for type 1 choledochal cyst is surgical excision with hepaticojejunostomy.

Ultrasound is the initial imaging modality of choice. It shows fusiform or saccular dilatation of the biliary tree of varying size and involving the common hepatic duct or common bile duct with or without dilatation of proximal intrahepatic bile ducts. The gallbladder may be hypoplastic or duplicated. Abrupt transition between the dilated and non-dilated portions of the bile duct favours the diagnosis. Sludge or stones may develop within the cyst. Biliary scintigraphy with technetium-99m disofenin shows accumulation of isotope within the dilated portion. CT cholangiography is accurate in delineating the intrahepatic biliary tree but its use is limited by the high radiation dose. ERCP, PTC and intraoperative cholangiography are used to demonstrate anatomical details of the biliary tree and the pancreaticobiliary junction but they are all invasive procedures [4]. Cholangiography performed with PTC and ERCP carries potential risks of bleeding, perforation, biliary sepsis, bile leaks, bile peritonitis and acute pancreatitis. Also the use of anaesthesia for both types of procedure is not without complications, especially in the paediatric age group [2].

With advances in MRCP imaging, including faster image acquisition and newer sequences, this technique increasingly plays a more important role in biliary tract imaging. It is especially useful in the paediatric population as it is non-invasive and does not use ionising radiation. MRCP can provide data on biliary tree morphology and anomalous pancreaticobiliary duct union. Also it can provide information on stones within choledochal cysts which is comparable if not superior to conventional cholangiography for pre-operative assessment [2]. The application of MRCP in this case allowed a diagnosis to be made without the need for invasive investigation.