Sacral neuromodulation for faecal incontinence following obstetric sphincter injury - outcome of percutaneous nerve evaluation.

Aim: The purpose of this study was to assess the efficacy of percutaneous nerve evaluation (PNE) in women with faecal incontinence (FI) following obstetric anal sphincter injury and to relate the outcomes to baseline factors, with special emphasis on the extent of the sphincter defect.

Method: This was a prospective study at a tertiary colorectal referral unit at the University Hospital of North Norway conducted from 2012 to 2014. Sixty-three women underwent a 3-week PNE using a tined lead and the Verify external neurostimulator. The primary outcome was efficacy, defined as the percentage reduction in weekly FI episodes, and patients with a reduction of 50% or more were defined as responders. Baseline factors affecting the primary outcome were explored. Sphincter defects were classified with a validated three-dimensional endoanal ultrasound defect score.

Results: Fifty-six (89%) of the 63 women were responders with a reduction in weekly FI episodes of 94.5%, from a median (interquartile range) of 4.8 (2.0-11.0) to 0.5 (0-2.0) (P < 0.001). Twenty-nine (52%) reported no weekly FI episodes, and urgency episodes disappeared in 18 (32%). In the multivariable linear regression model, efficacy was related to concomitant urinary incontinence (P = 0.04), body mass index (BMI) (P = 0.03) and pain during PNE (P = 0.046) but not to the extent of the sphincter defect (P = 0.1). Responders had a higher St Mark's score than nonresponders (P = 0.046).

Conclusions: The vast majority of women had successful PNE tests. Responders had higher baseline St Mark's scores than nonresponders. Efficacy was related to concomitant urinary incontinence, BMI and pain, not to the extent of the sphincter defect.