Gut Liver.  2017 Mar;11(2):196-208. 10.5009/gnl16126.

Small Intestinal Bacterial Overgrowth and Irritable Bowel Syndrome: A Bridge between Functional Organic Dichotomy

Affiliations
  • 1Department of Gastroenterology and Microbiology, Sanjay Gandhi Postgraduate Institute of Medical Sciences, Lucknow, India. udayghoshal@gmail.com

Abstract

The pathogenesis of irritable bowel syndrome (IBS), once thought to be largely psychogenic in origin, is now understood to be multifactorial. One of the reasons for this paradigm shift is the realization that gut dysbiosis, including small intestinal bacterial overgrowth (SIBO), causes IBS symptoms. Between 4% and 78% of patients with IBS and 1% and 40% of controls have SIBO; such wide variations in prevalence might result from population differences, IBS diagnostic criteria, and, most importantly, methods to diagnose SIBO. Although quantitative jejunal aspirate culture is considered the gold standard for the diagnosis of SIBO, noninvasive hydrogen breath tests have been popular. Although the glucose hydrogen breath test is highly specific, its sensitivity is low; in contrast, the early-peak criteria in the lactulose hydrogen breath test are highly nonspecific. Female gender, older age, diarrhea-predominant IBS, bloating and flatulence, proton pump inhibitor and narcotic intake, and low hemoglobin are associated with SIBO among IBS patients. Several therapeutic trials targeting gut microbes using antibiotics and probiotics have further demonstrated that not all symptoms in patients with IBS originate in the brain but rather in the gut, providing support for the micro-organic basis of IBS. A recent proof-of-concept study showing the high frequency of symptom improvement in patients with IBS with SIBO further supports this hypothesis.

Keyword

Bacterial overgrowth; Dysbiosis; Breath tests; Gastrointestinal microbiota; Probiotics; Rifaximin

MeSH Terms

Adult
Anti-Bacterial Agents/therapeutic use
Biopsy/methods
Blind Loop Syndrome/diagnosis/*microbiology/therapy
Breath Tests/methods
Female
Humans
Intestine, Small/*microbiology/pathology
Irritable Bowel Syndrome/complications/*microbiology
Male
Middle Aged
Probiotics/therapeutic use
Risk Factors
Anti-Bacterial Agents
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