LabMed

Gastrointestinal (GI) Angiodysplasia

At a Glance

Gastrointestinal (GI) angiodysplasia is a relatively common lesion of the mucosa and submucosa of the GI track, caused by small vascular malformations or ectasias, that is part of the normal aging process. Along with diverticulosis, it is one of the most common causes of unexplained lower GI bleeding and iron deficiency anemia in patients older than 60 years of age with the majority being older than 70 years of age. It has been estimated that between 5 and 6% of all GI bleeding episodes are due to angiodysplasia. There is no sex or racial predilection.

The lesions are often multiple, and although up to 80% involve the ascending colon, they can occur at any place in the GI track. When other parts of the GI track are affected, patients are usually younger than 50 years of age and the lesions are typically due to congenital malformations. Although overt bleeding due to angiodysplasia can be significant, it is normally sporadic and painless. In elderly patients, the most obvious symptoms due to angiodysplasia are weakness, fatigue, and shortness of breath caused by anemia.

For some patients, there may be no signs of overt bleeding directly from the colon, instead such patients may present with dark or black, tarry stools. Other patients may have occasional bleeding episodes with bright red blood from the rectum. Although bleeding will normally stop spontaneously in more than 90% of patients, it usually reoccurs. Mortality due to angiodysplasia, although rare, is related to the severity of bleeding and is impacted by patient age, hemodyamic instability, and the presence of other comorbid conditions.

Angiodysplasia along with diverticulosis and adenocarcinomia of the colon should be part of the differential diagnosis when a patient presents with unexplained iron deficiency anemia and/or a positive fecal occult blood test (FOBT). However, since bleeding due to angiodysplasia can be sporadic, the FOBT may, at times, be negative. Angiodysplasia can also be an incidental finding in up to 1% of elderly patients during routine colonoscopy screenings as recommended by the American College of Gastroenterology.

What Tests Should I Request to Confirm My Clinical Dx? In addition, what follow-up tests might be useful?

There are no specific laboratory tests that identify angiodysplasia. However, there are a number of tests that indicate the presence of chronic or acute GI bleeding. Approximately 10% of patients with angiodysplasia present with iron deficiency anemia, and, thus, a complete blood cell (CBC) count and serum iron levels would be useful. In addition, 10-15% of patients with angiodysplasia are intermittently positive for FOBT.

Diagnosis of angiodysplasia is usually accomplished by endoscopy, either colonoscopy or esophagogastroduodenscopy (EGD), although the lesions can be difficult to identify. With adequate bowl preparation, the sensitivity of colonoscopy for detecting angiodysplasia exceeds 80%. It is recognized by the cherry-red flat lesion(s) consisting of dilated blood vessels that radiate from a central vessel. A pale mucosal halo may also be visible around the lesion, which typically has a diameter of 2-10 mm. It is important to remember that the use of meperidine (Demerol) for sedation and analgesia may transiently diminish mucosal blood flow, which decreases the sensitivity of colonoscopy to detect angiodysplasia.

It has also been found that, in patients who have received meperidine, administration of naloxone can enhance the lesion(s) due to angiodysplasia. Unfortunately, administration of naloxone can result in discomfort to the patient when the procedure is prolonged by therapeutic intervention.

A relatively new technique, pill enteroscopy, has been a major advance in diagnosis of bleeding disorders of the GI track, especially in the small bowl, which is difficult to reach with traditional endoscopy. With this technique, a pill containing a video camera and radio transmitter is swallowed and pictures of the small intestine are sent to a receiver worn by the patient. However, if a lesion is identified, additional diagnostic/therapeutic techniques, such as double-balloon enteroscopy, which is a technique involving a long endoscopic camera and overtube filled with balloons, is still be required.

In cases with negative endoscopic finding but with a high clinical suspicion of angiodysplasia, selective angiography of the mesenteric arteries may be necessary. However, this technique is only useful if active bleeding is occurring during the test and, thus, has a sensitivity of only 58-86%.

Are There Any Factors That Might Affect the Lab Results?

Iron deficiency anemia will occur anytime a patient does not have enough iron to produce hemoglobin. As such, any condition that causes blood loss, such as peptic ulcer, hiatal hernia, colorectal cancer, or a lack of or the inability to absorb iron in a patient's diet, will lead to a decrease in the iron stores, resulting in a hypochromic, microcytic anemia. GI bleeding can also be a result of regular aspirin use or other nonsteroidal anti-inflammatory drugs.

The FOBT test can have false positive results if patients do not adhere to special diets (i.e., meat free and without vegetables, such as turnips and horseradish, that have peroxidase activity) and avoid excess levels (>250 mg/day) of vitamin C for at least 72 hours prior to testing. As mentioned, aspirin and other nonsteroidal anti-inflammatory drugs may cause bleeding in the GI track and should be avoided for 7 days prior to testing. In addition, with this test, it can be difficult to obtain patient compliance, as 3 separate stool specimens at least 1 day apart are recommended for optimal results. A positive FOBT is made by observing a color change in the presence of added hydrogen peroxide when the peroxidase in the fecal blood catalyzes the oxidation of guaiac.

The fecal immunochemical test, also called an immunochemical fecal occult blood test (iFOBT), is a newer test that also detects occult blood in the stool. This test is specific for human hemoglobin, which is found in red blood cells, and will not react with animal hemoglobin. The iFOBT is done essentially the same way as the FOBT, but patients may find it easier, because there are no dietary restrictions. However, patients should still refrain from ingesting aspirin and other nonsteroidal anti-inflammatory drugs. The iFOBT is also less likely to react to bleeding from parts of the upper GI track, such as the stomach.

What Lab Results Are Absolutely Confirmatory?

The Gold standard for the diagnosis of angiodysplasia is endoscopy, either colonoscopy or EGD.

Additional Issues of Clinical Importance

Bleeding from angiodysplasia lesions in both the upper and lower GI track has been reported in patients with von Willebrand disease. Since both von Willebrand disease and angiodysplasia have an underlying endothelial defect, there has been a link proposed between the 2 disorders. However, similar to patients with chronic renal failure requiring dialysis, a coagulopathy is more likely responsible for bleeding than an actual link.

Angiodysplasia has also been reported associated with aortic stenosis, although the bleeding is probably due to an underlying undiagnosed angiodysplasia and the result of a hematologic defect, such as a significant reduction/lack in high molecular weight von Willeband factor multimers, rather than an actual link. Patients with CREST, a form of systemic sclerosis (scleroderma), may also have a higher incidence of angiodysplasia throughout the GI track.

Errors in Test Selection

As mentioned, endoscopy, either colonoscopy or EGD, is considered the Gold standard for the diagnosis of angiodysplasia. Errors may be made if the patient is not prepared properly, which will impede observation of the upper and lower GI mucosa.

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