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 (stretching) of colonic veins, venules, and capillaries. The dilation becomes so severe that a small direct passageway develops between the artery and vein (arteriovenous fistula). 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. Men and women are equally at risk for developing angiodysplasia of the colon. Most patients are older than 50 years.
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