Choledochal or hydatid cyst: a clinical pitfall

 Human hydatidosis is responsible for approximately 1% of admissions to surgical wards in endemic region such as Iran [1]. Prevalence of hydatid disease was higher in western regions of Iran such as Khuzestan [2]. In our province the liver (60.5%) was the most commonly involved organ and icterus was noted in 22.5% of cases [3]. The diagnosis is based on enzyme-linked immunosorbent assay (ELISA) for echinococcal disease. Hydatid cyst of the biliary tract is very rare and only 3 cases have been reported so far.

The most probable differential diagnosis of hydatidosis of the biliary tract is choledochal cyst. Choledochal cysts are due to congenital dilatations of the biliary tree. The estimated incidence of choledochal cysts is 1 case in 13,000 to 1 case in 2 million live births [4].

We present a case is which there was no obvious difference preoperatively between choledochal and hydatid cyst. Sometimes there is no distinct pattern for differentiation of hydatid and choledochal cyst in such cases radiographically.

The patient is a 24-year-old woman who was admit­ted to hospital for evaluation of icterus, intermittent abdominal pain and itching for the last 4 weeks. She also suffered from dark urine and colorless stool (no his­tory of fever or weight loss). The only positive fin­ding on physical examination was mild jaundice. Labo­­ratory findings were as follows: hemoglobin, 12.6 g/dl;­ white blood cell count: 10 400/mm3 with no eosinophilia, bilirubin: 5.2 mg/dl with conjugated fraction of 3.1 mg/dl alkaline phosphatase, 2278 U/l, aspartate aminotransferase (AST): 208 U/l, alanine aminotransferase (ALT): 264 U/l. IgG antibody for hydatid disease was negative. Other laboratory data were within normal limits. Abdominal ultrasonography (US) showed a distended intrahepatic biliary system, common bile duct (CBD) and gall bladder. There was also an echo-free cystic lesion measuring 50 mm in the projection of the head of the pancreas with pressure effect on the distal portion of the CBD. Computed tomography (CT) scan of the abdomen confirmed the cystic lesion with thin wall medial to the duodenum, both intra- and extrahepatic dilation and relative distention of the pancreatic duct and gall bladder (Figure 1). Endoscopic retrograde cholangiopancreatography (ERCP) (Figure 2) and magnetic resonance cholangiography (MRC) (Figure 3) were performed. A cystic mass suggestive of a type I choledochal cyst in the proximal part of the...


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