Congenital absence of the portal vein: case report and MR demonstration.

Congenital absence of the portal vein (CAPV) is a rare anomaly that results from aberrant venous development in early embryonic life. The intestinal and splenic venous drainage bypasses the liver and drains directly into the inferior vena cava (IVC), the left renal vein, or the left hepatic vein. We describe a case where prenatal ultrasonography demonstrated an unusual C-shaped vessel between the umbilical vein and a dilated IVC, and failed to show a portal vein. Ultrasonography and magnetic resonance imaging and magnetic resonance angiography at 4 months of age again found no portal vein. The superior mesenteric vein drained into the left renal vein.