A Blinded Randomized Controlled Clinical Trial Comparing Sacral Nerve Modulation and Anal Bulking Injections as Treatment for Fecal Incontinence After Obstetric Anal Sphincter Injuries (OASIS).

Obstetric anal sphincter injuries (OASIS) is the most common cause of fecal incontinence (FI) in women. Obstetric-related FI may occur early after childbirth. Previous obstetric injury is also a major cause of FI in older women, and risk of FI increases with time and further childbirths. FI is involuntary loss of solid or liquid stool. Symptoms range from fecal urgency, soiling, to daily passive or urge fecal incontinence. FI is a stigmatizing condition. It can have a distressing impact and restriction on quality of life, including isolation and depression.

Tears during delivery is classified (Sultan) as first degree tears including vaginal epithelium, second degree tears into the perineal muscle, third degree involving the anal sphincter complex and fourth degree including sphincter complex and anorectal epithelium. OASIS includes third and fourth degrees tears.

First line of therapy of FI is conservative treatment including drug therapy and "biofeedback". If conservative treatment fails, surgery may be an option. Traditionally elective secondary sphincter repair has been performed at least once. Sphincter repair may improve symptoms in short time, but efficacy deteriorates with time.

Other minimal invasive surgical alternatives includes sacral nerve modulation (SNM) and anal bulking injection. Sacral nerve modulation involves stimulating the sacral nerves, usually S3 or S4. Step one is a trial period of temporary stimulation (PNE test). If the test is successful, the patient can have an implantable stimulator (step 2) to modulate sacral nerve function. SNM is also beneficial for treating FI after OASIS, and SNM is a alternative to secondary sphincter repair. SNM should possibly be preferred second line treatment also after sphincter tears related FI. Transanal submucosal bulking injection of collagen is also a possible treatment option and can be an effective treatment for both anal and fecal incontinence.

The purpose of this study is to compare the efficacy of sacral nerve modulation to anal bulking injections in women with fecal incontinence after OASIS through a Scandinavian multicenter single-blinded, randomized controlled trial.