Caput medusae

Caput medusae is the appearance of distended and engorged superficial epigastric veins, which are seen radiating from the umbilicus across the abdomen. The name caput medusae (Latin for "head of Medusa") originates from the apparent similarity to Medusa's head, which had venomous snakes in place of hair. It is also a sign of portal hypertension. When the portal vein, that transfers the blood from the gastrointestinal tract to the liver, is blocked, the blood volume increases in the peripheral blood vessels making them appear engorged. It is caused by dilation of the paraumbilical veins, which carry oxygenated blood from mother to fetus in utero and normally close within one week of birth, becoming re-canalised due to portal hypertension caused by liver failure.The appearance is due to cutanous portosystemic collateral formation between distended and engorged paraumbilical veins that radiate from the umbilicus across the abdomen to join systemic veins.

Inferior vena cava obstruction

 * Produces abdominal collateral veins to bypass the blocked inferior vena cava and permit venous return from the legs.

Determine the direction of flow in the veins below the umbilicus. After pushing down on the prominent vein, blood will:
 * flow toward the legs → caput medusae
 * flow toward the head → inferior vena cava obstruction.
 * Color Doppler ultrasonography is used to differentiate between vena cava obstruction and portal hypertension