gastrointestinal disorders
Small Intestinal Bacterial Overgrowth (SIBO)
Diagnosis of SIBO
Breath tests Quantitative culture of intestinal aspirate Imaging studies Some clinicians advocate response to empiric antibiotic therapy as a diagnostic test. However, because bacterial overgrowth can mimic other malabsorptive disorders (eg, Crohn Disease ) and adverse effects of the antibiotics can worsen symptoms of diarrhea, establishing a definitive etiology is preferred. (See also the American Journal of Gastroenterology's2020 guidelines for small intestinal bacterial overgrowth.) Breath testing,specifically with glucose hydrogen orlactulosehydrogen, is suggested in symptomatic patients for the diagnosis of small intestinal bacterial overgrowth (SIBO). Before breath testing, it is recommended that patients avoid use of antibiotics for 4 weeks and avoid promotility agents and laxatives for at least 1 week. A positive breath test is defined as a > 20-ppm increase of hydrogen from baseline in the first 90 minutes or a > 10-ppm increase of methane at any point during the test (see the American Journal of Gastroenterology's2020 guidelines for small intestinal bacterial overgrowth). The standard for diagnosis of SIBO isquantitative culture of intestinal fluid aspirateshowing a bacterial count>103colony-forming units/mL. This method, however, requires endoscopy. If the anatomic alterations are not due to previous surgery, an upper gastrointestinal series with small-bowel follow-through should be done to identify predisposing anatomic lesions. Alternatively, CT enterography or magnetic resonance enterography can be done. 