Small intestinal bacterial overgrowth: American College of Gastroenterology guidelines

  • Am J Gastroenterol

  • Jenny Blair, MD
  • Clinical Essentials
L'accesso ai contenuti di questo sito è riservato agli operatori del settore sanitario italiano L'accesso ai contenuti di questo sito è riservato agli operatori del settore sanitario italiano


  • Small intestinal bacterial overgrowth (SIBO) and methane overgrowth may be separate entities, according to guidelines published by the American College of Gastroenterology.
  • SIBO remains poorly understood.

Why this matters

  • SIBO has been linked to a host of diseases.
  • Reversible sequelae include malabsorption, micronutrient deficiencies.
  • Treatment remains nonstandardized.


  • Issued with Practice Parameters Committee of the American College of Gastroenterology.
  • Includes suggestions for trial design.

Key details

  • Defined as either:
    • Duodenal/jejunal aspirate finding ≥103 colony-forming units/mL; or
    • Breath test: after oral intake of glucose (75 g) or lactulose (10 g), subsequent rise in exhaled hydrogen of ≥20 parts per million above baseline within 90 minutes.
  • When considering diagnosis, weigh risk factors, including previous treatments of other conditions.
  • Authors recommend breath testing for patients with irritable bowel syndrome, suspected symptomatic motility disorders, or previous luminal abdominal surgery, but not for asymptomatic patients taking proton-pump inhibitors.
    • Use glucose hydrogen or lactulose hydrogen.
    • Sensitivity, specificity are low.
  • If excessive methane on breath, authors propose new entity, intestinal methanogen overgrowth, recognizing archaea overgrowth.
  • They recommend assessing methane via breath tests for symptomatic patients with constipation.
  • As treatment, authors suggest antibiotics (e.g., rifaximin), ideally after objective diagnosis.
  • Evidence is scarce regarding low-FODMAP diet, probiotics, intestinal microbiota transplant. 
  • All recommendations are conditional, with very low level of evidence.