New type of asymptomatic congenital portosystemic shunt

Congenital extrahepatic portosystemic shunt (CEPS) is an extremely rare anomaly. In these malformations splanchnic blood bypasses the liver and drains into the systemic circulation through the inferior vena cava (IVC) or the left renal vein (LRV). Extrahepatic shunts may be divided into type 1 [end-to-side mesenterico-caval fistula with congenital absence of the portal vein (PV)] and type 2 (partial portocaval shunt caused by side-to-side mesenterico-caval fistula with normal or hypoplasic PV). Type 2 shunts typically are wholly extrahepatic between the PV or its right branch and the retrohepatic IVC. This report describes an asymptomatic case of CEPS not previously documented and not classifiable as type 1 or 2. CT revealed a normal PV with communication between the inferior mesenteric vein (IMV) and the LRV. The inferior mesenteric vein appeared tortuous, abnormally long and with a large calibre, and presented a connection with the LRV, in addition to a normal confluence into the splenic vein. Colour Doppler revealed hepatopetal normal flow in the PV and superior mesenteric vein with mild portal hypertension and an inversion of flow in the IMV directed to the LRV. Biochemical parameters showed a normal liver function without hyperammonaemia.