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Tests and diagnosis
By Mayo Clinic staffThe first step in diagnosing blind loop syndrome is usually an abdominal X-ray or an abdominal computerized tomography (CT) scan, an X-ray technique that produces more detailed images of the body than conventional X-rays do.
You may also have additional tests to check for bacterial overgrowth in your small intestine, for poor fat absorption or for other problems that may be causing or contributing to your symptoms:
- Barium X-ray of the small intestine. This test uses a contrast dye (barium) to coat the lining of your intestine so that it stands out clearly on X-rays. A barium X-ray may reveal a blind loop, diverticulosis, a narrowing (stricture) of the intestine or other anatomical problems as well as slow transit times that can cause bacterial overgrowth.
- Hydrogen breath test. Several breath tests are used to check for bacterial overgrowth. Because fermenting carbohydrates release hydrogen, this test measures the amount of hydrogen in your lungs after you drink a mixture of glucose and water. A rapid rise in hydrogen indicates poor carbohydrate digestion and bacterial overgrowth in your small intestine. Although widely available, the test is less sensitive than other breath tests are.
- D-xylose breath test. In this test, which is more accurate than is a hydrogen breath test, you ingest a type of sugar called xylose. If unusual numbers of bacteria are present in your small intestine, they metabolize the xylose, releasing carbon dioxide in the process. Breath carbon dioxide is measured every half-hour for two hours.
- Bile acid breath test. In your small intestine, bile acids from your liver help emulsify and digest fats (lipids). But proliferating bacteria interfere with this process, leading to poor absorption of both fats and carbohydrates. This test uses a bile salt (glycocholate) bound to a small amount of radioactive material to check for bile salt dysfunction in your small intestine.
- Quantitative fecal fat test. This test may be used to determine how well fats are absorbed. Most often, you eat a high-fat diet for three days. The amount of fat in your stool is then measured. Large amounts of undigested fat indicate malabsorption, one cause of which is bacterial overgrowth.
- Small intestine aspirate and fluid culture. This is the most sensitive test for bacterial overgrowth, but it's invasive and technically difficult to perform. To obtain the fluid sample, doctors pass an endoscope down your throat and through your digestive tract to your small intestine. A sample of intestinal fluid is withdrawn with the endoscope and then placed in a culture medium in a laboratory where it's observed for the growth of bacteria.
