Normally closed portosystemic collaterals that may open in the setting of portal hypertension include the paraumbilical vein, spleno-renal collaterals, and spleno-retroperitoneal collaterals. In patients with portal hypertension, a re-canalized paraumbilical vein will extend beyond the anterior liver surface and show hepatofugal venous flow. Spleno-renal shunts can often be identified with the patient in a right lateral decubitus position. If the shunt itself cannot be visualized, high velocities in the left renal vein would be an indirect sign of such a shunt.
