[Small intestine bacterial overgrowth: Myths and realities]

The small intestine bacterial overgrowth (SIBO) is a clinical disorder resulting from colonization of the small intestine by an excessive number of microorganisms or by unusual microorganisms. When they are methane producers it is called intestinal methanogen overgroth (IMO). Known risk factors are congenital or acquired anatomical alterations, motility alterations, some systemic and autoimmune diseases, those that cause alterations in biliopancreatic secretions, hypochlorhydria and some drugs. It causes abdominal pain and distension, bloating, diarrhea, nausea, and weight loss, which can occur in different diseases or with intestinal malabsorption. In IMO there may be constipation. Suggestive analytical data may be iron deficiency, anemia, deficiency of fat-soluble vitamins or B₁₂. The breath test with detection of exhaled H₂ is the most accessible technique, but requires rigorous performance and interpretation. The central treatment is oral antibiotics, rifaximin of choice, but they are empirical and should only be prescribed in the event of high clinical suspicion.