Tests and diagnosis

By Mayo Clinic Staff

The first step in diagnosing blind loop syndrome is usually an imaging test, such as:

  • Abdominal X-ray
  • Abdominal CT scan

You may have additional tests to check for bacterial overgrowth in your small intestine, poor fat absorption, or other problems that may be causing or contributing to your symptoms:

  • Barium X-ray of the small intestine. This test uses a contrast solution (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 structural problems, as well as slow transit times that can cause bacterial overgrowth.
  • CT enterography. This test is more sensitive than is a barium X-ray or conventional CT. It helps detect inflammation or structural problems in the bowel and abnormalities in other organs, such as the pancreas.
  • Hydrogen breath test. This test measures the amount of hydrogen that you breathe out after drinking 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, this test is less sensitive than other breath tests.
  • D-xylose breath test. This test, which is more accurate than a hydrogen breath test, measures the amount of carbon dioxide in your breath. High levels of carbon dioxide suggest bacterial overgrowth.
  • Bile acid breath test. Bile acids from your liver help digest fats (lipids) in your small intestine. Bacterial overgrowth interferes with the process. This test uses a bile salt with a radioactive tracer to check for bile salt dysfunction.
  • Quantitative fecal fat test. This test can determine how well your small intestine absorbs fat. You eat a high-fat diet for three days, and the amount of fat in your stool is then measured. Large amounts of undigested fat may be caused by bacterial overgrowth, but more commonly result from other conditions such as short bowel syndrome or chronic pancreatitis.
  • Small intestine aspirate and fluid culture. This is the most sensitive test for bacterial overgrowth. To obtain the fluid sample, doctors pass a long, flexible tube (endoscope) down your throat and through your upper digestive tract to your small intestine. A sample of intestinal fluid is withdrawn and then tested in a laboratory for the growth of bacteria.

If your doctor believes that bacterial overgrowth is very likely, he or she may begin treatment with antibiotics immediately without specific testing.

Feb. 26, 2015