Congenital choledochal cyst in an infant with cystic fibrosis.

Congenital choledochal cyst is malformation of the biliary ductal system, which rarely occur. We describe here a 4-month old boy, who was referred to our center with respiratory distress and low level consciousness. In physical examination, a mass was detected in right upper quadrant of abdomen. Sonographic examination indicated a cystic structure representing the choledochal cyst. Further evaluation confirmed the diagnosis of cystic fibrosis in this patient. Although choledochal cyst is considered as a rare disease, it is the most frequent malformation of the extrahepatic biliary ducts, which easily could be misdiagnosed.