Posterior Tibial Nerve Stimulation for the Treatment of Fecal Incontinence Following Obstetric Anal Sphincter Injury

Abstract

Obstetric anal sphincter injuries (OASI) are a major risk factor for fecal incontinence (FI). Neuromodulation is often used as second-line therapy for FI, but evidence for its efficacy is conflicting. We aimed to evaluate the efficacy and predictive factors of posterior tibial nerve stimulation for obstetric anal sphincter injury-induced FI. Consecutive females with FI related to past OASI who had not responded to first-line therapy and had received 8-12 weeks of posterior tibial nerve stimulation were included. Subjects aged more than 50 and/or having other causes of FI were excluded. Patients underwent anorectal physiology and endoanal ultrasound pretherapy. Symptom burden was evaluated pretherapy and posttherapy using Rockwood and Wexner scales. A Wexner score reduced to below 10 or halved was used to define responders. A total of 37 females (mean age 38 years, median parity 2) were included. About 17 (46%) had ultrasonographically visualized anal sphincter defects and 41% had a history of third or second-degree perineal tears. About 14 subjects (38%) were deemed responders. Compared with nonresponders, responders had lower baseline rectal distension thresholds and tended to have disrupted (59%) than intact sphincters (20%, p < 0.01). Responders demonstrated improvement in Rockwood score for depression and embarrassment, visual analogue score for bowel symptoms and stool consistency (median baseline Bristol score 5, to 3 posttherapy; p < 0.01). Of a well-defined cohort of females with FI secondary to OASI, 38% responded to posterior tibial nerve stimulation. Much of this improvement may relate to improvement in stool consistency.