Abernethy malformations manifest as hepatopulmonary syndrome, pulmonary vasculopathy, or encephalopathy. A novel intervention in a child with portosystemic shunt and inferior caval vein hypoplasia led to complete normalisation of hypoxia and relief of obstruction in the inferior caval vein. Embryological explanations of venous anomalies may indicate that inferior caval vein anomalies are frequent but under-recognised in patients with Abernethy malformation.