Sacral nerve modulation (SNM) is an established treatment for refractory lower urinary tract and bowel dysfunction (Spinelli 2008). Pudendal nerve stimulation (PNS) has been proposed for patients failing SNM treatment of urinary dysfunction (Spinelli 2005). In this study SNM and PNS are compared for the treatment of fecal incontinence. In a test phase, both treatments will be applied for one week each in a randomized and blinded order (cross-over design). After the test phase the more successful treatment will be determined and applied permanently. If both treatments are equally sufficient, PNS will be chosen for permanent stimulation, since preliminary data indicate that PNS has a lower power consumption than SNM. Lower power consumption results in a longer lifetime of the stimulator, thus requiring less replacement surgeries.

Primary Surgery:

• Implantation of two electrodes, one placed next to the sacral nerve, one close to the pudendal nerve. Electrode wires are passed through the skin just above the gluteal region and are marked S and P. One of the sub-investigators (not involved in the follow-up) replaces the S and P marks by 1 and 2 marks in absence of the operating surgeon. Assignment of 1 and 2 is carried out in a predefined randomized fashion (computerized block randomization).

Test phase:

• Electrode labeled 1 is connected to a stimulator and the nerve is stimulated for one week, then the other electrode is stimulated for a week.
• Based on bowel habit diary, Wexner score (Jorge 1993) and subjective experience of the patient, the more successful treatment is chosen. If both electrodes were equally successful, the pudendal nerve electrode will be chosen for permanent stimulation.

Secondary surgery:

• After unblinding, the less effective electrode is removed and the remaining electrode is connected to an implanted stimulator (permanent phase). In case both treatments were unsuccessful, both electrodes are removed.

Inclusion Criteria:

• fecal incontinence nonresponsive to conservative treatment

Exclusion Criteria:

• sacral or perineal infection
• sphincter defect larger than 60° (sonography)
• pregnancy