Small Intestinal Bacterial Overgrowth in Irritable Bowel Syndrome : A Systematic Review and Meta-Analysis of Case-Control Studies

A questionnaire to establish the presence of 15 symptoms thought to be typical of the irritable bowel syndrome (IBS) was given to 109 unselected patients referred to gastroenterology or surgery clinics with abdominal pain or a change in bowel habit or both. Review of case records 17--26 months later established a definite diagnosis of IBS in 32 patients and of organic disease in 33. Four symptoms were significantly more common among patients with IBS--namely, distension, relief of pain with bowel movement, and looser and more frequent bowel movements with the onset of pain. Mucus and a sensation of incomplete evacuation were also common in these patients. The more of these symptoms that were present the more likely was it that the patient's pain or altered bowel habit, or both, was due to IBS. We conclude that a careful history can increase diagnostic confidence and reduce the amount of investigation in many patients with chronic abdominal pain.

A growing number of studies seem to suggest that small intestinal bacterial overgrowth (SIBO) is a common clinical problem. Although various techniques are available to make this diagnosis, tradition has accepted small bowel aspirate (>10(5) cfu/ml) as a gold standard. In this systematic review, the validity of culture and other diagnostic testing for SIBO is evaluated. We performed a systematic review of the literature from 1966 to present using electronic databases (PubMed and OVID). Full paper review of those abstracts that fulfilled preset criteria was carried out to evaluate the validity of various tests in diagnosing SIBO. Finally, all papers were evaluated against published standards for studies on diagnostic testing. Seventy-one papers met the criteria for detailed review. Studies were very heterogeneous with regards to patient populations, test definitions, sample size, and methods in general. Small bowel colony counts appeared elevated in most gastrointestinal diseases compared to controls. The traditional definition of >10(5) cfu/ml was usually indicative of stagnant loop conditions. Although, numerous diagnostic tests were studied, not even culture papers met the quality standards described by Reid et al. Breath testing and other diagnostic testing suffered therefore from the lack of a gold standard against which to validate in addition to the poor quality. There is no validated diagnostic test or gold standard for SIBO. In this context, the most practical method to evaluate SIBO in studies at this time would be a test, treat, and outcome technique.

Hydrogen breath tests using various substrates like glucose, lactulose, lactose and fructose are being used more and more to diagnose small intestinal bacterial overgrowth (SIBO) and lactose or fructose malabsorption. Though quantitative culture of jejunal aspirate is considered as gold standard for the diagnosis of SIBO, hydrogen breath tests, in spite of their low sensitivity, are popular for their non-invasiveness. Glucose hydrogen breath test is more acceptable for the diagnosis of SIBO as conventionally accepted double-peak criterion on lactulose hydrogen breath test is very insensitive and recently described early-peak criterion is often false positive. Hydrogen breath test is useful to diagnose various types of sugar malabsorption. Technique and interpretation of different hydrogen breath tests are outlined in this review.