Sacral nerve stimulation induces changes in the pelvic floor and rectum that improve continence and quality of life

Sacral nerve stimulation (SNS) can improve fecal incontinence, though the exact mechanism is not known. This study examines the following hypotheses: SNS leads to contraction of the pelvic floor, influences rectal perception, and improves continence and quality of life.

Fourteen patients with sacral nerve stimulators implanted for fecal incontinence were examined prospectively. Morphological and functional assessment was done by endosonography, manometry, and volumetry with the stimulator turned on and off in direct succession. Questionnaires were used to determine incontinence and quality of life.

With the stimulator turned on, rectal filling conditions were perceived only at higher volumes; in particular, the defecation urge was sensed only at higher volumes. There was also a reduction in the diameters of the external and internal anal sphincters and a decrease in the distance between the anal mucosa and the symphysis as a sign of pelvic floor elevation. Six months after surgery, continence and quality of life were markedly better than before the operation.

We were able to confirm the hypotheses given above. The improvements of pelvic floor contraction and rectal perception are rapid adjustment processes in response to stimulation of sacral nerves S3/S4 when turning on the stimulator.