Caput medusae is a medical term used to describe a condition where swollen, or engorged, veins appear on the belly, or abdomen. The veins run outward in all directions from the belly button, or umbilicus, and are twisted in shape. In Latin, caput medusae means the head of Medusa. Medusa was a monster in Greek mythology who had hair made out of snakes. The twisting pattern of veins on the abdomen is thought to resemble this.
A condition known as portal hypertension typically causes caput medusae. In portal hypertension, there is abnormally high pressure in what is called the portal circulation. The portal circulation consists of a system of veins that carries nutrients from the gut, spleen, and pancreas to the liver. Pressure within the system can rise due to an increased flow of blood entering it, or as the result of an obstruction. The obstruction could occur at any point between the blood leaving the gut, spleen, and pancreas, its passage through the liver and its exit into the systemic veins which drain into the heart.
Cirrhosis of the liver is one of the common causes of portal hypertension. The disease causes damage to the liver, distorting the channels that carry blood within it. As it becomes more difficult for blood to flow through the liver, pressure builds up in the portal circulation and the body attempts to bypass it by opening up alternative networks of veins. These networks connect the portal system with the systemic circulation that returns blood to the heart from the rest of the body.
One of these bypass networks typically forms in what are called the paraumbilical veins, around the umbilicus, causing them to enlarge to create the caput medusae. With a large caput medusae, it is sometimes possible to hear blood humming inside the veins. The sound becomes louder when the person breathes in, and is known as a Cruveilhier-Baumgarten murmur.
Other sites where veins become similarly swollen include the point where the esophagus, or food pipe, meets the stomach and around the rectum, the last part of the gut, from which feces leaves the body. Portal hypertension can result in fluid building up, causing swelling of the belly and legs, and an enlarged spleen. The breasts may become swollen and the umbilicus might stick out.
Management of portal hypertension involves treating the underlying cause. In the case of cirrhosis, a liver transplant may be necessary. Occasionally, fluid in the abdomen may need to be drained, and surgery may be carried out to stop bleeding from veins around the esophagus.