Caput medusae

Caput medusae is the appearance of distended and engorged umbilical veins which are seen radiating from the umbilicus across the abdomen to join systemic veins.

Etymology
The name caput medusae (Latin for "head of Medusa") originates from the apparent similarity to Medusa's hair once Minerva had turned it into snakes.

Causes
It is a sign of severe portal hypertension that has decompressed by portal-systemic shunting through the umbilical veins.

Inferior vena cava obstruction

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

How to differentiate
Determine the direction of flow in the veins below the umbilicus.
 * Caput Medusae - flow is towards the legs
 * Inferior vena cava obstruction - flow is towards the head.