Background: Various bulking agents have been used to treat fecal incontinence. While short-term outcomes are attractive, there is still a lack of long-term data. The aim of this systematic review and meta-analysis was to investigate the midterm outcomes of treatment with injectable bulking agents and to identify predictive factors for improvement in incontinence.
Methods: PubMed, EMBASE, Web of Science, and Cochrane Library databases were searched using the terms injection, bulking agents, and fecal incontinence. Studies with a minimum follow-up of 1 year were included. The improvement rate in incontinence was calculated by percent change in validated fecal incontinence score (FIS) following injection treatment. To explore the impact of predictive factors on improvement in incontinence, univariate meta-regressions were conducted using the random-effect model.
Results: A total of 889 patients in 23 articles were included. The weighted mean follow-up duration was 23.7 months (95% CI 19.3-28.2). Eleven different bulking agents were used. Four validated FISs were used. The Cleveland Clinic Fecal Incontinence score (CC-FIS) was used in 19 studies. Most studies reported a statistically significant improvement in FIS. The pooled mean preoperative CC-FIS (n = 637) was 12.4 (95% CI 11.4-13.3). The pooled mean CC-FIS at last follow-up (n = 590) was 7.7 (95% CI 6.1-9.3). The weighted mean difference in CC-FIS between preoperative visit and last follow-up was 4.9 (95% CI 4.0-5.8). Hence, the rate of improvement in incontinence was 39.5% based on CC-FIS. Meta-regression revealed that the perianal injection route and implants intact on endoanal ultrasonography were predictive of greater improvement in incontinence. The manometric data revealed that the initial increase in the mean resting pressure following injection was attenuated over time. The pooled rate of adverse events was 18.0% (95% CI 10.0-30.1). In most cases, adverse events were minor and resolved within a couple of weeks.
Conclusions: Administration of injectable bulking agents results in significant midterm improvement in FIS. Perianal injection route and implants intact on EAUS were predictive of higher improvement in incontinence. However, given the paucity of randomized controlled trials in the literature, further research is needed to improve the quality of the evidence.
Keywords: Fecal incontinence; Injectable bulking agents; Midterm outcomes.