The purpose of this systematic review is to evaluate whether implantable versus injectable bulking agents (second-line therapies) are equal/superior in terms of effectiveness (severity, quality of life [QoL], sustainability) and safety (adverse events) for fecal incontinence (FI).

A systematic review was conducted and five databases were searched (Medline via Ovid, Embase, Cochrane Library, University of York Centre for Reviews and Dissemination, and International Network of Agencies for Health Technology Assessment database). In-/exclusion criteria were predefined according to the PICOS scheme. The Institute of Health Economics risk of bias (RoB) tool assessed studies’ internal validity. According to the Grading of Recommendations, Assessment, Development and Evaluation (GRADE) approach, the strength of evidence for safety outcomes was rated. A qualitative synthesis of the evidence was used to analyse the data.

Six prospective uncontrolled trials (143 patients) were included. The evidence consists of six prospective single-arm, before-after studies fulfilling the inclusion criteria for assessing clinical effectiveness and safety for implantable bulking agents. FI severity (Cleveland Clinic FI Score) statistically significantly improved to three months (p<0.01) and six months (p<0.05) follow-up (five studies). Improvements in severity sustainability were reported after 12, 14 (p<0.01), and 36 (p<0.0001) months postoperatively. Improved disease-related QoL (FI QoL Score) was found (p<0.05) 12 months after surgery, and statistically significant improvements in QoL’s sustainability after 12 months (one study).

Procedure-related adverse events (n=3) occurred, where prostheses extruded during surgery, and anal discomfort/pain was felt (n=11). Device-related adverse events, i.e., prostheses’ dislodgement (n=31) and removed/extruded prostheses (n=3), occurred. Studies were judged with moderate/high RoB. The strength of evidence for safety was judged to be very low.

Implantable bulking agents might be an effective and safe minimally invasive option in FI treatment if conservative therapies fail. FI severity significantly improved, but not QoL, which needs to be explored in further studies. Due to the uncontrolled nature of the case series, comparative studies need to be awaited.