Colonic arteriovenous malformation

Alternative names
Vascular ectasia of the colon; Angiodysplasia of the colon; Colonic angiomas


Angiodysplasia of the colon is a condition of dilated and fragile blood vessels in the colon that results in intermittent loss of blood from the gastrointestinal tract. The condition is mostly related to the aging and 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. It is different than diverticulosis, another very common cause of bleeding in older adults.

Causes, incidence, and risk factors

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.


The symptoms can vary. Often in elderly patients, the symptoms are anemia, weakness, fatigue, and shortness of breath. There may not be any signs of bleeding directly from the colon. Others may have intermittent mild or severe bleeding episodes with bright red blood coming from the rectum.

Some patients may have dark or black, tarry stools. There is no pain associated with angiodysplasia.

Signs and tests

Colonoscopy - Examining the walls of the colon using a camera on the end of a long tube inserted into the rectum.

Angiography - Injecting dye into the veins to visualize any leakage of the dye from the arteries/veins into the colon. This is visualized with x-rays. This test is only useful if there is active bleeding into the colon.

CBC - A blood test that measures the amount of red blood cells in your system. A low amount suggests bleeding from the colon.

Stool guaiac - A test to look for blood in the stool that cannot be seen by the naked eye. Small amounts of stool are placed on 3 cards and analyzed at the doctor’s office. The samples are checked for any evidence of blood. A positive test result suggests bleeding from the colon.


When a patient is bleeding from the colon, it is important to determine the source of the bleeding and the rate of blood loss. The patient’s condition must be evaluated continuously and may require admission to an intensive care unit (ICU). Administration of IV fluids, and administration of blood products may be required.

Once the source of the bleeding is found (usually by angiography or colonoscopy), treatment can begin. As many as 90% of vascular ectasias stop bleeding spontaneously without any specific intervention.

When intervention is needed, however, the colonoscope can cauterize (burn) the site of hemorrhage. This procedure can be done electrically, with heat or with a laser. Complications of this procedure include perforation of the colon, as well as possible treatment failure.

Actively bleeding vascular ectasia can also be treated by angiography by clotting the blood supply to the bleeding area of the colon. The use of chemicals that cause the blood vessels to constrict can also be administered, whether by angiography or colonoscope.

In some instances, surgery is the only option. A right hemicolectomy, or removal of the entire right side of the colon, may be required. This remains the treatment of choice for a patient whose ectasia continues to bleed at a dangerously quick rate, despite several therapeutic interventions by angiography and colonoscopy.

Expectations (prognosis)

As mentioned above, bleeding in more than 90% of instances stops spontaneously. However, patients who have bleeding angiodysplasia despite having had colonoscopy, angiography, or surgery, are likely to have recurrent bleeding in the future.

The goal of repeat endoscopic therapy is to reduce, if not totally eliminate, the number of bleeds, hospitalizations, and transfusions. Surgery may be curative in some cases. Prognosis remains good if the bleeding is controlled.


  • Severe loss of blood from the gastrointestinal tract  
  • Anemia  
  • Death from excessive blood loss

Calling your health care provider

Call your health provider if rectal bleeding or black stools occur.


No measures are available at this time.

FAQ (Frequently Asked Questions):

How do I know if I have angiodysplasia of the colon?

You don’t. The only way to find out is if you have evidence of bleeding from your GI tract, and a colonoscopy supports this finding. Otherwise, the symptoms are the same as any other condition that causes bleeding from the gastrointestinal tract, with the caveat that this disease does not cause pain.

Should everyone be tested for angiodysplasia of the colon?

No. Only if you have evidence of bleeding from your gastrointestinal tract.

Johns Hopkins patient information

Last revised: December 8, 2012
by Brenda A. Kuper, M.D.

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