This is a condition with dilated and fragile blood vessels in the colon that results in intermittent loss of blood from the gastrointestinal tract. The condition is largely related to the aging/degeneration of the blood vessels, as it occurs in older adults.

Angiodysplasia of the colon is not related to cancers or other congenital disease of the blood vessels, and it is different than diverticulosis (another very common cause of bleeding in older adults).

There are several theories about the cause of angiodysplasia of the colon. The most likely is that normal contractions of the colon result in dilation of colonic veins/venules/capillaries. The dilation becomes so severe that a small direct communication between the artery and vein (arteriovenous fistula) is produced. It is in this area of the colon wall that the patient is at risk for bleeding.

Angiodysplasia of the colon has been seen in about 3% of "nonbleeding persons" and in about 5% of patients evaluated for blood in the stool, anemia, or hemorrhage. There is no sex predilection for angiodysplasia of the colon. Most patients are older than 50 years.