Caput medusae is a clinical sign on an x-ray during pregnancy where the veins leading from the umbilical cord to the abdomen. The veins form a pattern similar to the snakes on Medusa's head in mythology. It also looks similar to a palm tree and is often called palm tree sign. It is a sign of high blood pressure in the veins from the liver and is caused when the flow of blood uses the umbilical cord as a by-pass. It can be a sign of liver failure.