Sacral nerve stimulation for faecal incontinence alters colorectal transport

Sacral nerve stimulation reduces the frequency of defaecation in patients with faecal incontinence. The aim of this study was to examine the mechanism behind the reduced number of bowel movements in incontinent patients treated with sacral nerve stimulation.

The study included 20 patients with faecal incontinence and a positive percutaneous nerve evaluation test: 19 women and one man, with a median age of 63 (range 28-78) years. Colorectal scintigraphy was performed to assess colorectal emptying at defaecation before and after implantation. Segmental colorectal transit times were determined using radio-opaque markers.

The median frequency of defaecation per 3 weeks decreased from 56 (range 19-136) to 26 (range 12-78) (P < 0.002). At defaecation, antegrade transport from the ascending colon decreased from a median score of 8 (range 0-23) to 0 (range 0-11) per cent (P = 0.001), while retrograde transport from the descending colon increased from a median score of 0 (range 0-14) to 2 (range 0-30) per cent (P = 0.039). The median defaecation score was unchanged. There was a non-significant increase in median total gastrointestinal transit time from 2.5 (range 0.9-6.2) to 3.3 (range 0.8-6.2) days (P = 0.079).

Sacral nerve stimulation reduces antegrade transport from the ascending colon and increases retrograde transport from the descending colon at defaecation. This may prolong colonic transit time and increase the storage capacity of the colon.