S1142 Short-Term and Long-Term Outcomes of Fecal Microbiota Transplantation for the Treatment of Irritable Bowel Syndrome: A Systematic Review and Meta-Analysis

Introduction: Irritable bowel syndrome (IBS) is a chronic functional gastrointestinal disorder that significantly impairs the quality of life. Although its etiology is multifactorial, dysbiosis, or an imbalance in the gut microbiota, it is increasingly recognized as a potential contributor to its pathophysiology. The role of fecal microbiota transplantation (FMT) in managing IBS symptoms remains inconclusive, and studies on the long-term outcomes of FMT are limited. This study aimed to evaluate the short- and long-term efficacy of FMT in the treatment of IBS. Methods: We conducted a comprehensive literature search of several databases from their inception through April 2025. Studies have investigated the short- and long-term efficacy of FMT compared with placebo in adult patients (≥18 years old) with IBS. The outcomes of interest were clinical response (CR), defined as either the resolution or improvement in IBS symptoms, IBS symptom severity score (IBS-SSS), IBS Quality of Life questionnaire (IBS-QoL), and adverse events. The random-effects model was used to calculate the standardized mean difference (SMD) and odds ratio (OR) with corresponding 95% confidence intervals for desired outcomes. Statistical significance was set at P value < 0.05. Heterogeneity was assessed using the I2 Index. Data analysis was performed using the Revman software (version 5.4.1). Results: Twelve RCTs were included, with a total population of 607, of which 58.31% received FMT. The participants had an average age of 41.3, and 65.7% were women. Diarrhea-predominant IBS was the most common type, followed by mixed-type IBS. Compared to placebo, FMT is associated with improvement of IBS-QoL at 12 months (SMD 0.68, 95% CI 0.20-1.16), and 24 months (SMD 0.91, 95% CI 0.18-1.64) but at longer follow up of 54 weeks, no difference was found between the 2 groups in IBS-QoL (SMD 0.49, 95% CI -0.04 - 1.01). No significant difference was found in CR at 12 weeks (OR 2.84, 95% CI 0.68 - 11.97), IBS-SSS at 12 weeks (SMD -0.40, 95% CI -1.07 - 0.26), and 24 weeks (SMD -0.39, 95% CI -1.58 - 0.80). FMT was not associated with serious adverse events (OR 1.32, 95% CI 0.60 - 2.92). Conclusion: This study does not support FMT as a successful treatment strategy for IBS because of suboptimal clinical improvement. FMT improves the quality of life in the short term for IBS but is not maintained beyond 12 months. However, larger studies with longer follow-up periods are needed to examine the role of FMT in IBS.