Angiodysplasia of the colon is enlarged and fragile blood vessels in the colon that result in occasional loss of blood from the gastrointestinal (GI) tract.

Angiodysplasia of the colon is mostly related to the aging and degeneration of the blood vessels. It usually occurs in older adults.

There are several theories about the cause. The most likely cause is that normal spasms of the colon lead to enlargement of blood vessels in the area. This swelling becomes so severe that a small direct passageway develops between a very small artery and vein. This is called an arteriovenous fistula. It is in this area of the colon wall that the patient is at risk for bleeding.

Angiodysplasia of the colon is very rarely related to other diseases of the blood vessels, including Osler-Weber-Rendu syndrome. It is not related to cancer, and is different than diverticulosis, another very common cause of intestinal bleeding in older adults.