Angiodysplasia

(Vascular Ecstasias)

Small clusters of dilated and tortuous veins in the mucosa of the colon and small intestine, which may cause lower GI bleeding.

Angiodysplasia occurs in > 25% of persons >= 60 and is an important cause of acute and major lower GI bleeding as well as of slow intermittent blood loss in the elderly. Repeated episodes of low-grade, partial obstruction of submucosal veins are believed to occur when colonic muscles contract or when intraluminal pressure increases, resulting in venous dilation and tortuosity. Mucosal veins drained by the submucosal vein may also be affected. In the final stage of development, the precapillary sphincter becomes incompetent, and a small arteriovenous communication with the ectatic tuft of vessels develops. Angiodysplasia usually develops in the right colon, probably because tension on the bowel wall is greater, as expressed by Laplace's law relating tension to the diameter of the bowel lumen. A causal association between angiodysplasia and aortic stenosis has been questioned after a thorough review of the literature.

Symptoms, Signs, and Diagnosis

Mucosal angiodysplasia is asymptomatic in most persons. Patients usually present with painless, subacute, and recurrent bleeding, which stops spontaneously in the vast majority of cases. Bleeding may be red blood, maroon stools, or melena, or it may be occult. About 10 to 15% of patients have episodes of brisk blood loss.

Diagnosis may be made by colonoscopy or mesenteric angiography. Colonoscopy is preferred because it can exclude other causes of bleeding and can also be used as a therapeutic intervention. Because lesions are small, often multiple, and difficult to see, the colon must be thoroughly cleansed to allow for adequate visualization of the mucosa. Cleansing is usually performed after bleeding has stopped, preferably within 48 hours so that other sources of bleeding (eg, diverticula or ischemia) can be identified. Meperidine should not be used to sedate patients undergoing colonoscopy because it makes identification of ectasias more difficult; if meperidine is required, naloxone can be administered during the procedure to enhance visualization.

Mesenteric angiography is preferred when acute bleeding is brisk. Advanced angiodysplasia is indicated by tortuous, densely opacified clusters of small veins that empty slowly. Arteriovenous communication is indicated by early filling of the vein and is found in most patients evaluated for bleeding. When bleeding is active (>= 0.5 to 1.0 mL/minute), the contrast medium is extravasated into the bowel lumen, but because bleeding is often intermittent, extravasation is seen in only a minority of patients. However, scintigraphy with technetium Tc-99m- labelled red blood cells may locate a bleeding site. This technique detects active bleeding at rates of 0.05 to 0.1 mL/minute, and the patient can be serially scanned for up to 36 hours if bleeding is intermittent.

Treatment

Conservative treatment with blood or iron replacement as appropriate may be all that is necessary. Diet and the use of laxatives, analgesics, and other drugs are outlined in Table 107-1. When bleeding is recurrent, transcolonoscopic electrocoagulation or laser coagulation may be attempted. Difficulties include identifying the ectatic lesions and excluding other causes of blood loss if bleeding has stopped. Also, perforation of the right colon is a recognized hazard of coagulation therapy.

Active, severe bleeding may be controlled quickly by intra-arterial or IV administration of vasopressin 0.2 to 0.6 U/min, which often stabilizes the patient for more definitive treatment. If coagulation therapy is not technically possible or if acute bleeding cannot be controlled, surgery is required. If the right colon is the only identified source of bleeding, a right hemicolectomy is performed. However, after such surgery, bleeding recurs in up to 20% of patients, who then require a more extensive colonic resection or exploratory laparotomy.

Small-bowel enteroscopy may eventually reduce the need for diagnostic laparotomy in patients with recurrent bleeding from obscure sites. For these patients, estrogen-progesterone therapy may decrease transfusion requirements.