Abernethy malformation type II masquerading as unexplained hypoxemia in early childhood: a case report

Abernethy malformation-congenital extrahepatic portosystemic shunt (CPSS)-is rare and frequently misattributed to cardiopulmonary disease. Early recognition is crucial to prevent multisystem complications.

A 30-month-old girl with heterotaxy spectrum and a history of device-closed ductal/ventricular septal defects presented with recurrent hospitalizations labeled as viral-induced wheeze and persistent hypoxemia requiring prolonged oxygen therapy. During an intercurrent rhinovirus/enterovirus infection she could not be weaned below 0.5-1 L/min oxygen despite clinical resolution, with orthodeoxia. Agitated-saline contrast echocardiography showed delayed appearance of bubbles in the left heart consistent with intrapulmonary shunting, alongside interrupted IVC with azygos continuation. CT angiography demonstrated situs inversus with levocardia, polysplenia, and a congenital extrahepatic portosystemic shunt consistent with Abernethy Type II. Staged endovascular reduction of shunt flow was recommended. Following the first stage (partial closure to maintain portal patency), oxygenation improved, however nocturnal oxygen was still required at time of follow-up, while awaiting the second stage treatment.

In young children with unexplained, persistent hypoxemia-especially with heterotaxy or prior congenital heart disease-Abernethy malformation should be considered. Bedside bubble echocardiography can trigger definitive cross-sectional imaging and expedite curative intervention.