Aspiration of<unk> from the jejunum is the gold standard for diagnosis. A<unk>  load of greater than 105<unk> per millilitre is diagnostic for<unk><unk>  The diagnosis of<unk><unk>  can be made by physicians in various ways. Malabsorption can be detected by a test called the D-xylose absorption test. Xylose is a sugar that does not require enzymes to be digested. The D-xylose test involves having a patient drink a certain quantity of D-xylose, and measuring levels in the urine and blood; if there is no evidence of D-xylose in the urine and blood, it suggests that the<unk>  bowel is not absorbing properly (as opposed to problems with enzymes required for digestion). The gold standard for detection of<unk><unk>  is the aspiration of more than 105<unk> per millilitre from the<unk>  bowel. The normal<unk>  bowel has less than 104<unk> per millilitre. Some experts however, consider aspiration of more than 103 positive if the flora is predominately colonic type<unk> as these types of<unk> are considered pathological in excessive numbers in the<unk>  intestine. The reliability of aspiration in the diagnosis of<unk>  has been questioned as<unk>  can be patchy and the reproducibility can be as low as 38 percent. Breath tests have their own reliability problems with a high rate of false positive. Some doctors factor in a patients' response to treatment as part of the diagnosis. Biopsies of the<unk>  bowel in<unk><unk>  can mimic celiac disease, with partial villous atrophy. Breath tests have been developed to test for<unk><unk> . These tests are either based on<unk>  metabolism of carbohydrates to hydrogen, methane, or hydrogen sulfide, or based on the detection of by-products of digestion of carbohydrates that are not usually metabolized. The hydrogen breath test involves having the patient fast for a minimum of 12 hours then having them drink a substrate usually glucose or lactulose, then measuring expired hydrogen and methane concentrations typically over a period of several hours. It compares well to jejunal aspirates in making the diagnosis of<unk><unk> . Carbon-13 (13C) and carbon-14 (14C) based tests have also been developed based on the<unk>  metabolism of D-xylose. Increased<unk>  concentrations are also involved in the deconjugation of bile acids. The glycocholic acid breath test involves the administration of the bile acid 14C glycocholic acid, and the detection of 14CO2, which would be elevated in<unk><unk> . However, some physicians suggest that if the suspicion of<unk><unk>  is high enough, the best diagnostic test is a trial of treatment. If the symptoms improve, an empiric diagnosis of<unk><unk>  can be made. There is insufficient evidence to support the use of inflammatory markers, such as fecal calprotectin, to detect<unk> .
Small intestinal bacterial overgrowth
Autoimmune gastrointestinal dysmotility
Intestinal neuronal dysplasia
Foreign body in alimentary tract
Exocrine pancreatic insufficiency
Glucose-galactose malabsorption
Fructose malabsorption
Food protein-induced enterocolitis syndrome