Caput medusae is the appearance of distended and engorged paraumbilical veins

Paraumbilical veins

In the course of the round ligament of liver and of the median umbilical ligament, small veins are found which establish an anastomosis between the veins of the anterior abdominal wall and the hepatic portal, hypogastric, and iliac veins....

, which are seen radiating from the umbilicus

Navel

The navel is a scar on the abdomen caused when the umbilical cord is removed from a newborn baby...

 across the abdomen to join systemic veins. The name caput medusae (Latin for "head of Medusa") originates from the apparent similarity to Medusa

Medusa

In Greek mythology Medusa , " guardian, protectress") was a Gorgon, a chthonic monster, and a daughter of Phorcys and Ceto. The author Hyginus, interposes a generation and gives Medusa another chthonic pair as parents. Gazing directly upon her would turn onlookers to stone...

's hair once Athena

Athena

In Greek mythology, Athena, Athenê, or Athene , also referred to as Pallas Athena/Athene , is the goddess of wisdom, courage, inspiration, civilization, warfare, strength, strategy, the arts, crafts, justice, and skill. Minerva, Athena's Roman incarnation, embodies similar attributes. Athena is...

 had turned it into snakes .

Inferior vena cava obstruction

• Cirrhosis cause portal hypertension.
• Produces abdominal collateral veins to bypass the high pressure portal system and permit venous return from the leg
  Leg
  Łęg may refer to the following places in Poland:*A former name for the town of Ełk *Part of the Czyżyny district of Kraków*Łęg, Pleszew County in Greater Poland Voivodeship...
  
  s.

How to differentiate

Determine the direction of flow in the veins below the umbilicus. After pushing down on the prominent vein, blood will:

• Caput Medusae - flow is towards the legs
• Inferior vena cava obstruction - flow is towards the head.