A rare Abernethy Ib malformation was initially misdiagnosed as chronic portal vein thrombosis in a 27-year-old female.

Abernethy malformation or congenital portosystemic shunt is a rare congenital vascular malformation and anomaly of the splanchnic venous system defined by diverting portal blood away from the liver. It is commonly associated with multiple congenital anomalies. Imaging modalities such as computed tomography or magnetic resonance have a crucial role in prompting diagnosis and determining the prognosis based on the type of malformation and associated anomalies. Misdiagnosis could be harmful and may lead to inappropriate treatment. We present a case of Abernethy malformation with a complete end-to-side shunt of portal venous flow into the systemic venous flow and complete bypass of the liver, which was initially misdiagnosed with portal venous thrombosis.