Sacral neuromodulation: does it affect the rectoanal angle in patients with fecal incontinence?

In the past decade numerous studies have been published on the successful treatment of fecal incontinence with sacral neuromodulation (SNM). The underlying mechanism of action for lower bowel motility disorders has been unclear. In the present study, the effect of SNM on the rectoanal angle in patients with fecal incontinence was investigated.

In 12 consecutive patients who qualified for SNM an X-defecography study was performed before SNM and at 6 months after permanent implant. Three single lateral rectal views were taken: one during rest, one during squeeze, and one during Valsalva's maneuver, after which the patient was asked to evacuate as rapidly and completely as possible during lateral fluoroscopy. At 6 months two further defecography studies were performed, one during stimulation with the pacemaker on and one with the pacemaker off.

The defecography studies showed that the rectoanal angle decreased during rest, squeeze, and Valsalva's maneuver. A slight increase in rectoanal angle was seen during defecation. However, the differences did not reach statistical significance. Sacral neuromodulation improved fecal continence significantly in all patients at 6 months. Median incontinence episodes per week decreased from 6.2 to 1.0 (P = 0.001), and incontinent days per week decreased from 3.7 to 1.0 (P = 0.001) with SNM. There were no significant changes in the median resting and squeeze anal canal pressures, 46.5 versus 49.7 mmHg and 67.1 versus 72.3 mmHg, respectively. Median stimulation amplitude at follow-up was 2.7 V (range: 0.9-5.3 V).

Rectoanal angle did not decrease significantly in patients with fecal incontinence during SNM.