Prenatal ultrasound demonstration of a choledochal cyst.

Choledochal cysts and cystic biliary atresia are very uncommon, especially in neonates. An incidence of one case per two million has been recorded (McNulty, 1977). A case is presented where a choledochal cyst was demonstrated at 36 weeks' gestation by ultrasound examination and a firm preoperative ultrasound diagnosis established within two days of birth, thereby facilitating early treatment. We believe this to be the earliest demonstration of a choledochal cyst reported in the English literature. A 24-year-old primigravida was referred for ultrasound examination at 36 weeks' gestation because of the clinical suspicion of hydramnios. The examination confirmed the presence of hydramnios and the gestational age of the fetus. In addition, two fluid-filled structures were identified in the upper abdomen of the fetus (Fig. 1). These were interpreted as representing the distended stomach and duodenum analogous to the “double bubble” sign and a diagnosis of duodenal atresia was suggested. A second examination at...