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 immuno-sorbent 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 hydati-dosis of the biliary tract is choledochal cyst. Choledoch-al 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 hy-datid 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 his tory 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/mm 3 with no eosino-philia, 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 aminotrans-ferase (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 chol-angiopancreatography (ERCP) (Figure 2) and magnetic resonance cholangiography (MRC) (Figure 3) were performed. A cystic mass suggestive of a type I choledoch-al cyst in the proximal part of the distended CBD was reported. Both the CBD and pancreatic duct were communicating with the choledochal cyst and gall bladder. …