The Effectiveness of Fecal Microbiota Transplant in Reducing Irritable Bowel Symptoms: An Updated Meta-Analysis and Systematic Review

Introduction: Irritable bowel syndrome (IBS) is a complex functional gastrointestinal disorder thought to be characterized by a dysbiosis of gut microbiota. Fecal microbiota transplantation (FMT) has been proposed as a potential treatment to restore gut microbiome diversity and provide symptomatic relief in patients with IBS. We conducted meta-analyses and a systematic review of currently available randomized controlled trials (RCTs) to evaluate the effectiveness of FMT in IBS. Methods: We conducted a systematic literature search of PubMed and Cochrane Central Register of Controlled Trials. Our selection criteria included RCTs which measured the efficacy of FMT vs placebo treatments in IBS patients. Meta-analyses were conducted to evaluate the relative risk (RR) with a 95% confidence interval (CI) of FMT vs placebo with the primary outcome being reduction in IBS symptoms and the secondary outcome to assess the effectiveness of single-dose FMT vs double-dose FMT. Results: Of the 750 studies that were identified by our database search, 17 were found to be relevant. 7 of those studies, comprising 538 patients met the inclusion criteria. FMT had no significant improvement in the reduction of IBS symptoms as compared to the standard placebo treatment (RR=1.14; 95% CI 0.84-1.55), however subgroup analyses revealed that multiple dose FMT (RR=0.54; 95% CI 0.34-0.85) had a decreased likelihood of reducing IBS symptoms, while single-dose FMT (RR=1.40; 95% CI 1.20-1.64) had increased likelihood of reducing IBS symptoms when compared with the placebo and this was statistically significant. Conclusion: Our results are similar to the last meta-analysis with evidence suggesting that FMT does not yield a significant benefit in relieving IBS symptoms. Subgroup analyses resulsts are still perplexing as it would seem reasonable that if a single-dose FMT improves IBS symptoms, then a double-dose treatment would as well. This may be due to the overwhelming nature of excess gut microbiota in the colon, thereby exacerbating clinical symptoms in these patients. Further randomized control trials should be conducted to not only continue to look at the effect of FMT for IBS symptom reduction, but also to answer why certain doses may have better clinical outcomes.Figure 1.: The Forrest Plot depicted is separated into the overall effectiveness of FMT in the reduction of IBS symptoms as well as stratified to analyze the effectiveness of single-dose vs double-dose FMT.