Vanishing prenatal sub-hepatic cyst associated with biliary atresia: A case report

Introduction: Biliary atresia (BA) is the result of a progressive obliterative cholangiopathy that begins in the perinatal period. Cystic BA (CBA) is a subtype of BA that can be misdiagnosed easily as a choledochal cyst (CC) during the prenatal period. These two diseases, however, differ widely in their prognosis so differentiating them soon after birth if critical.Case presentation: A fetus was initially suspected to have a CC after a sub-hepatic cyst was detected by prenatal ultrasonography (US) at 16 weeks of gestation. Follow-up serial US showed a gradual decrease in the size of the cyst. The cyst disappeared towards the end of the pregnancy. A CC was excluded because it is an irreversible bile duct dilatation. BA was suspected and confirmed after birth. The patient underwent a Kasai portoenterostomy was 15 days after birth. We believe that a sub-hepatic cyst was formed during bile duct obliteration in the early fetal period, but the cyst involuted progressively and disappeared in the later fetal period. Conclusion: Fetuses who have sub-hepatic cysts that decrease in size over time and disappear towards the end of the gestation should be monitored for cholestasis because it appears that such imaging findings can be associated with biliary atresia.