Abstract
Reporting a rare case of spontaneous perforation of intrahepatic choledochal cyst arising from tertiary intrahepatic branch of left hepatic duct and extending up to the liver surface in a four year old child. The child in addition had a Hydatid cyst in the right lobe of liver. The perforation was closed with an omental filler and the biliary tract drained through gall-bladder. The hydatid cyst in the right lobe was enucleated at the same time.

Introduction
Choledochal cyst, or congenital dilatation of the common bile duct, was first reported clinically by Douglas in 1852. Various classifications have been described either based on anatomy or on cholangiographic findings. The most commonly used classification is that of Alonzo-Lej which describes Intrahepatic choledochal cysts as Type IV (wherein there are multiple cysts of intra or extra-hepatic ducts or both) and Type V (as single or multiple intrahepatic cysts). Most of the choledochal cysts are extrahepatic.

Case Report
A four year old male child came to us with pain in the right hypochondrium, vomiting and fever of three days duration. He did not have any jaundice. On per abdominal examination a significant finding was tender hepatomegaly (liver size 4 cms. subcostally). An abdominal ultrasound scan showed two cysts one in the right lobe and one in the left lobe of liver measuring 10 cms and 4 cms respectively. A tentative diagnosis of hydatid cyst was made and child was started on Albendazole and planned for routine surgery. Two days before the day of surgery child developed sudden distension of abdomen and shock. An emergency laparotomy was performed, presuming ruptured hydatid cyst. After draining two litres of bile from the peritoneal cavity, a 4 cms ruptured cyst was found on the undersurface of the left lobe of liver. An intraoperative cholangiogram was performed which showed a normal gall bladder, common bile duct and hepatic ducts and a choledochal cyst arising from one of the tertiary branches of the left hepatic duct. The choledochal cyst had ruptured, which came as a total surprise, and hence had dye leaking in the peritoneal cavity. The perforation was closed with an omental filler and the biliary tract drained through the gall bladder. In the right lobe of liver, hydatid cyst measuring 10 cms was found which was enucleated. 42 hours post-operatively the child succumbed to septicaemia.

Discussion
Solitary intrahepatic choledochal cyst is an extreme rarity. According to the classification, intrahepatic choledochal cysts fall into Type IV and V categories. In spite of extensive review of literature we could not find any reported case of a ruptured intrahepatic choledochal cyst. Of all the choledochal cysts, one to two per cent of patients present with cyst rupture and bile peritonitis.1 The reason for rupture of the cyst is not clear, though various theories have been put forward such as blunt abdominal trauma,2-4 increased intra-abdominal pressure due to vomiting,3 pregnancy,5 continuous reflux of pancreatic juice into the bile ducts as a result of malformation of pancreatobiliary system,6 and protein plugs occluding the distal bile ducts.7 None of the above causes could be found in our case.

Fig. 1 : Intra-operative cholangiogram showing normal gall-bladder, bile ducts, an intrahepatic choledochal cyst and site of leak – marked by an arrow.	Fig. 2 : Intra-operative picture showing perforation site in the left lobe of liver – marked by an arrow.

In a report by KC Tan,8 wherein they have presented a 14-year surgical experience of choledochal cysts, two patients had intrahepatic cysts. One of those had Type V (diffusely dilated and cystic intrahepatic ducts and normal extrahepatic ducts) choledochal cyst for which tube cholecystostomy was performed and debris flushed from the biliary tree. The other patient had both intra and extrahepatic cyst.

Involvement of intrahepatic bile ducts in choledochal cysts or multiple cysts of biliary tracts has been frequently reported, though none has reported perforation of intrahepatic cyst.

Hydatid cysts are endemic to certain areas. According to a report,9 about 100 children were evaluated. Again we could not find any reported case of hydatid cyst co - existing with choledochal cyst in the literature. In our case the choledochal cyst was an incidental finding. Treatment is directed to cystectomy with use of scolicidal agents such as cetrimide, 0.9% sodium chloride, hypertonic saline, formaldehyde, silver nitrate solution. To conclude, though we could not salvage this patient, we would like to highlight that an intrahepatic choledochal cyst could also rupture and requires prompt treatment.

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