Hydatid cyst of head of pancreas mimicking choledochal cyst

Abstract

A 5-year-old girl presented with abdominal pain, intermittent jaundice and a gall bladder lump. Clinical examination and preoperative imaging suggested the diagnosis of a type I choledochal cyst (CDC). During surgery, this was found to be a hydatid cyst (HC) occupying the head of pancreas causing obstruction to the common bile duct (CBD). A pancreatic HC mimicking a CDC and presenting with CBD obstruction is unusual.

Background

Hydatid cyst (HC) disease is endemic in many parts of the world. It can present in unusual ways. We report a 5-year-old girl having HC of the head of pancreas with clinical picture and preoperative imaging, mimicking a choledochal cyst (CDC). While managing a CDC, possibility of a HC must be considered till an on table confirmation is done.

Case presentation

A 5-year-old girl presented to us with a history of abdominal pain and intermittent jaundice for 6 months. She had remained afebrile and stools continued to be yellow. No history of contact with animals was given.

On examination, she weighed 13.5 kg and stood 99 cm tall (both below 3rd percentile for her age). Her vital signs were normal for her age.

There was no pallor, lymphadenopathy. She had icterus and the systemic examination showed a non-tender hepatomegaly of 5 cm and a palpable gall bladder lump.

Investigations

Her ultrasound and magnetic resonance cholangio-pancreaticogram (MRCP) showed a 12 cm × 10 cm cyst involving the common bile duct (CBD). There was dilatation of the hepatic ducts and intrahepatic biliary radicles. The pancreatic duct appeared to be opening into the cyst (figure 1).

Figure 1.

MRCP of the hydatid cyst giving the appearance of a choledochal cyst. P, pancreatic duct.

Her conjugated serum bilirubin was 2.9 mg/dl, alanine transaminase 218 IU/l, aspartate aminotransferase 227 IU/l, serum alkaline phosphatase was 1100 IU/l.

Treatment

With the MRCP picture being that of a CDC, the child was taken for a laparoscopic CDC excision. On laparoscopic examination, the location of the cyst appeared very distal and the upper CBD was found to be dilated but not a part of the swelling. The cyst was occupying the head of the pancreas. On aspiration, the cyst drained clear colourless fluid rather than bile. A conversion to open surgery was done using a right subcostal incision. Keeping the possibility of HC, the area was packed with chlorhexidine soaked mops and the cyst was incised on its superior aspect (figure 2) and aspirated. It revealed a pearly white membrane that was similar to a hydatid endocyst. Enucleation was done (figure 3). A cystogram was done to check for the pancreatic communication (figure 4) and none was found. A cholangiogram was done intraoperatively (through the gall bladder) that showed a smooth flow of dye into the duodenum. Cholecystectomy was done. An abdominal drain was left draining the cyst cavity and the hepatorenal pouch.

Figure 2.

Laparotomy picture showing the incision on the cyst behind the duodenum. Cyst was partly aspirated before opening it.

Figure 3.

Enucleated endocyst.

Figure 4.

Cystogram after enucleation.

Postoperative period was smooth. Patient was allowed for oral intake on the 2nd postoperative day (POD). Drain was removed on 5th POD and the child was discharged. Her chest x-ray was normal. Biopsy of the cyst confirmed that it was a HC.

Child was started on albendazole that was given for three cycles of 21 days each. Serum alkaline phosphatase level was monitored.

Outcome and follow-up

We intend to follow-up this patient both by radiology and serology.

Discussion

Paediatric HC disease commonly involves the lung and liver but unusual locations have been described in the children.¹ Five cases of pancreatic HC have been reported in paediatric population.^2–4 An unusual case of intraluminal obstruction of the CBD caused by an unruptured HC has also been reported.⁵ Only one case of extraluminal obstruction has been reported till date.⁶ HC within a CDC has also been reported.⁷ In this child, a solitary HC, involving the head of the pancreas presented with an extraluminal obstruction of CBD that mimicked a a CDC on preoperative imaging.

MRCP has been considered a good modality for preoperative imaging for CDC.^8–10 However, it may be unable to differentiate between a CDC and an HC if the latter is occupying unusual position as in our case. In a young child the possibility of CDC is high and with no history of exposure to animals, it is all the more difficult to preoperatively suspect an HC of the pancreas that may mimic a CDC.

Serology facilitates diagnosis of cystic hydatid disease and also is a useful tool for follow-up.¹¹ Antibody detection is more sensitive than detection of circulating antigen. Therefore, detection of antibody remains the method of choice. These tests employ the use of crude antigens such as hydatid fluid or protoscolex extracts.¹² Tests using recombinant or purified species-specific antigens may have add on values.

We did not undertake serology testing in our patient because our preoperative diagnosis was choledochal cyst.

Learning points.

• ▶HC is an important differential diagnosis in management of patients suspected to have CDC even in paediatric population.
• ▶Though very helpful, MRCP can have its pitfalls and a diagnostic aspiration of the cyst or a cholangiogram is essential during surgery before handing the cyst.
• ▶Laparoscopy has a role to play in management of cystic lesions in and around the choledochus.