While the literature includes much discussion regarding the relationship between intestinal microflora and various disorders, intestinal dysbiosis as a specific disorder is poorly defined. A literature search revealed no published studies establishing diagnostic criteria for this disorder. The gastrointestinal symptoms attributed to intestinal dysbiosis (i.e., bloating, flatulence, diarrhea, or constipation), overlap in part with either irritable bowel syndrome or small intestinal bacterial overgrowth syndrome. The diagnosis of irritable bowel syndrome is typically made clinically, based on a set of criteria referred to as the Rome criteria. The small intestine normally contains a limited number of bacteria, at least in comparison to the large intestine. Small intestine bacterial overgrowth may occur due to altered motility (including blind loops), decreased acidity, and exposure to antibiotics, or surgical resection of the small bowel. Symptoms include malabsorption, diarrhea, fatigue, and lethargy. Although the diagnosis of bacterial overgrowth may be made clinically and the condition treated empirically with antibiotics, the laboratory gold standard for diagnosis consists of a culture of a jejunal fluid sample. Recently, hydrogen breath tests, commonly used to evaluate lactose intolerance, have been adapted for use in diagnosing both small intestinal bacterial overgrowth and irritable bowel disease. No studies in the published literature were identified that described analysis of a stool sample as a diagnostic technique for irritable bowel syndrome or small intestine bacterial overgrowth.
Measurements of fecal fat (i.e., qualitative, quantitative, and fat differential) are established diagnostic techniques for malabsorption. In contrast, a literature search did not identify any published studies regarding the diagnostic performance of fecal analysis of digestion, absorption, microbiology, metabolic markers, or immunology as a workup of malabsorption syndrome, small intestine bacterial overgrowth, or intestinal dysbiosis. Chronic intestinal candidiasis has been linked with various gastrointestinal complaints as well as systemic complaints, such as chronic fatigue syndrome. Similar to intestinal dysbiosis, chronic intestinal candidiasis is an ill-defined condition without established diagnostic parameters.
A literature search of the MEDLINE database for the period of February 2005 to October 2007 did not identify any published articles on intestinal dysbiosis that would change the above conclusions; thus, the policy statement remains unchanged.
Recent literature has focused on the role of bacterial overgrowth of the small bowel in the pathogenesis of irritable bowel syndrome (IBS). These studies have used the hydrogen breath test to diagnose bacterial overgrowth, and have reported mixed results. Cuoco and Salvagnini reported that 45.8% (44/96) of patients with IBS had abnormal breath tests. In contrast, Walters and Vanner reported that only 10%–13% of patients with IBS had an abnormal breath test, and that this percentage of abnormal results did not differ from a group of healthy controls.
A number of clinical trials have been published that evaluate treatment of IBS patients with nonabsorbable antibiotics and/or probiotics. Two recent randomized, controlled trials of rifaximin versus placebo reported improvement in IBS symptoms following antibiotic treatment. Sharara and colleagues performed a hydrogen breath test pre- and post-treatment and found that response to treatment correlated with a change in the breath test.
Trials of treatment with probiotics have been less successful. Whorwell and colleagues treated IBS with the probiotic Bifidobacterium infantis and reported that there was symptom improvement with one of three doses, but no improvement with the other two doses. Niv and colleagues used the probiotic Lactobacillus reuteri in patients with IBS and did not find any significant reduction in symptoms compared with placebo.
In summary, some evidence is accumulating to suggest that bacterial overgrowth has a role in IBS, and that treatment with non-absorbable antibiotics may have a benefit in reducing symptoms for these patients. However, none of these studies has used fecal analysis to select patients or to monitor response to treatment. Therefore, the role of fecal analysis in evaluating and or treating intestinal dysbiosis remains uncertain, and there is no evidence to suggest that fecal analysis leads to improved health outcomes.
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