Hydatid cyst within a choledochal cyst.

A 5 year 4 months old male child presenting with pain abdomen and jaundice was diagnosed to have type 1 choledochal cyst on ultrasonography and magnetic resonance cholangio pancreatography. On exploration, the cystic dilatation of common bile duct was found to have a hydatid cyst (HC) inside it. The per-operative findings were confirmed by histopathology. Association of HC within a choledochal cyst is extremely rare and has been reported only twice before in the available English literature.

INTRODUCTION

Hydatid cyst (HC) is a common parasitic disease in the Indian subcontinent. It commonly involves the liver and lung, but other uncommon locations have been described in the literature.[1] Association of HC within a choledochal cyst is extremely rare and has been reported only twice before in the available English literature.

CASE REPORT

A child aged 5 years 4 months presented to our institute with the chief complaint of repeated attacks of pain over right upper abdomen for last 4 months. Parents noticed gradually increasing yellow discoloration of eyes for last 15 days. The child also had generalized itching all over the body and he was passing deep yellow colored urine and clay colored stool for the same duration. On clinical examination, patient was found to have deep jaundice. Epigastric tenderness was a prominent feature.

The child was admitted and investigated. The liver function tests were found to be grossly abnormal with high total and conjugated bilirubin. Prothrombin time was initially abnormal and came down to normal with treatment. Ultrasonography showed a dilatation of common bile duct (CBD) suggesting choledochal cyst [Figure 1]. Magnetic resonance cholangio pancreatography confirmed the diagnosis [Figure 2]. On exploration, the CBD was found to be dilated with a maximum diameter of about 3.5 cm. After dissection, choledochotomy was done and it revealed a cyst with yellowish white membrane suggesting bile-stained HC [Figure 3]. Extraction of the HC was performed followed by cholecystectomy and complete excision of the choledochal cyst with hepaticodochoduodenostomy. Post-operatively both resected specimen and the cyst within the CBD were sent for histopathological examination (HPE). The results of histopathology were confirmatory. Post-operative hippuric iminodiacetic acid scan showed normal flow of dye through hepaticodochoduodenostomy.

Figure 1

Ultrasonography showing cystic dilatation of the common bile duct

Figure 2

Magnetic resonance cholangiopancreatography showing type 1 choledochal cyst

Figure 3

Choledochotomy showing hydatid cyst within choledochal cyst

DISCUSSION

Pediatric HC disease commonly involves the lung and liver, but unusual locations like within the CBD, head of pancreas etc. have been described in children.[1234] Most of the cases of HC are asymptomatic. However when symptomatic, the usual presentation is with pain in right hypochondrium with obstructive jaundice due to obstruction of the biliary tree. Our case is a very rare combination of both the pathologies presenting together.

The differential diagnosis includes pancreatic HC, which can also mimic choledochal cyst leading to misdiagnosis as mentioned in the literature.[56]

Here, we discuss a very rare presentation of pediatric HC within a choledochal cyst type I variant. A similar case was described by Gopal in 1993[7] where the authors did choledochocystoduodenostomy because of dense adhesions around the cyst. However in our case, cholecystectomy along with complete cyst excision, hepaticodochoduodenostomy[8] and removal of HC was done, which is regarded as one of the standard approaches.

As per the editorial comment in the above article[7] the possibility that there was a small, primary intrahepatic cyst from which a small daughter cyst traversed the biliary system and got lodged in the CBD causing its gradual dilatation also came to our mind. To rule out this possibility, we sent the specimen of the choledochal cyst and the HC for detailed HPE. On HPE, it was confirmed that there was already a choledochal cyst, in which the HC (3.5 cm in its greatest axis) developed later making this case very unique and extremely rare. Patient had an uneventful post-operative period.

In our case, it is possible that the migration of embryos occurred via the portal circulation to the liver and then these embryos got lodged into the already formed choledochal cyst. The presence of the double pathology made the diagnosis difficult in our patient.

CONCLUSION

HC may lodge within a choledochal cyst also, which is a very unusual location for it. Though very unusual, it is very important to keep it in mind during the surgery of any child presenting to us with obstructive jaundice and pain, to prevent rupture and dissemination of the HC, which usually is diagnosed on the operating table in spite of all the relevant pre-operative investigations as seen in our case.