The diagnosis is established when the exhaled breath H 2 level increases by more than 10 parts per million greater than baseline on two consecutive samplings, or if the fasting breath hydrogen level exceeds 20 parts per million. įasting breath hydrogen is elevated in overgrowth patients, and early rises after glucose or lactulose challenge reflect small bowel fermentation of the substrate by abnormal concentrations of bacteria.Xylose is catabolized by gram-negative aerobes and is absorbed in the proximal small bowel. Glycocholic acid is released by bacterial deconjugation of radiolabeled bile acids. Radiolabeled breath tests using glycocholic acid or xylose have been used for diagnosis of overgrowth. Jejunal intubation can be performed endoscopically, and protected catheters can be used to obtain more reliable aspirates. Because the test is cumbersome, some clinicians rely on indirect testing. Additionally, bacterial overgrowth can be patchy and thus missed by a single aspiration. There is a risk of potential contamination by oropharyngeal bacteria during small bowel intubation. Jejunal intubation for aspiration with bacterial colony counts and stain identification can provide a definitive diagnosis by showing jejunal counts greater than 10 5 with colonic organisms. Osteomalacia, vitamin K deficiency, night blindness, hypocalcemic tetany, and vitamin E deficiency may ensue. Weight loss associated with clinically apparent steatorrhea has been observed in about one-third of patients with bacterial overgrowth severe enough to cause cobalamin deficiency. These would include patients with gastroparesis, irritable bowel syndrome, diabetes, and scleroderma. The clinical conditions that comprise dysmotility syndromes usually do not present with malabsorption due to the dysmotility per se but will have malabsorption, not infrequently, due to superimposed bacterial overgrowth. Again, it is important to underscore the observation that bacterial overgrowth may be superimposed on a number of common clinical conditions that may be primary causes of malabsorption, but the overgrowth that is present may be the most easily treatable part of the patient's malabsorption. Diagnosis should not be delayed until cobalamin malabsorption or steatorrhea is present.
it is now rather common that the presenting symptoms of a patient with bacterial overgrowth are often very nonspecific. The clinical features noted in patients with bacterial overgrowth are listed in Table II.