In the course of the round ligament of liver and of the median umbilical ligament, small veins (paraumbilical) are found which establish an anastomosis between the veins of the anterior abdominal wall and the hepatic portal, hypogastric, and iliac veins.
The best marked of these small veins is one which commences at the umbilicus and runs backward and upward in, or on the surface of, the round ligament (ligamentum teres) between the layers of the falciform ligament to end in the left portal vein.
In patients with portal hypertension, the paraumbilical veins may become enlarged in order to reduce hepatic portal vein pressure by shunting blood to the inferior epigastric vein. The inferior epigastric vein drains to the great saphenous vein to the femoral vein which ultimately drains into the inferior vena cava directly through the common iliac vein, thereby bypassing the liver. Dilation of this particular portacaval anastomosis results in what is referred to as caput medusae.