Antenatal diagnosis of biliary atresia (type I cyst) at 19 weeks' gestation: differential diagnosis and etiologic implications.

At 19 weeks' gestation, two cystic structures were first identified in the abdomen of a fetus. A repeat ultrasonography at 34 weeks confirmed a definite cyst communicating with the liver. The baby was born at 39 weeks, and serum direct bilirubin started to rise to 4.1 mg/dL. An operative cholangiogram at 23 days of life showed a cystically dilated choledochus with distal atresia and a relatively smooth yet hypoplastic intrahepatic biliary tree. Complete obliteration of the cystic duct was also noted. After excision of the cystic common bile duct, hepatico-jejunal anastomosis was performed, and the patient did well for 8 months postoperatively. Liver biopsy showed proliferation of the bile ductules, but no interlobular bile ducts were observed in any portal triad. A diagnosis of biliary atresia was established. Including the present case, five cases of antenatally diagnosed biliary atresia have been reported. All of them had type I cyst, and antenatal diagnosis was made at 19 to 32 weeks' gestation. Differential diagnosis between biliary atresia of type I cyst and choledochal cyst with complete distal obstruction has been a matter of discussion, and recognition of the entity of antenatally diagnosed biliary atresia is of significant importance from an etiological point of view.