Sacral nerve stimulation (SNS) is a new therapeutic option to treat fecal incontinence, although its mecanims of action remains poorly understood. The investigators hypothtized that SNS could act on enteric nervous system (ENS). To verify this hypothesis, the investigators will collect biopsy samples from patients implanted for SNS, and assess whether SNS induces changes in ENS.

Sacral nerve stimulation (SNS) is a new therapeutic option to treat fecal incontinence. Its efficacy yields 80% approximately, but its mecanims of action remains poorly understood. In particular, SNS does not restore anal squeezing contraction nor it increase anal tone. Recently, using a porcine model, it was shown that SNS changed colonic permeability, suggesting that SNS may activate the enteric nervous system (ENS).

The investigators hypothtized therefore that SNS could act on enteric nervous system (ENS).

To verify this hypothesis, the investigators will collect biopsy samples from patients before and after implantation for SNS. The investigators will assess whether SNS induces changes in ENS, and if this is correlated to SNS efficacy.

Inclusion Criteria:

• Fecal incotinence
• refractory to medial treatment
• Eligible to a treatment with sacral nerve stimulation

Exclusion Criteria:

• age < 18 yo
• age < 75 yo
• anal defect > 120°
• bilateral interruption of the bulbo-cavernous reflex
• patient not able to speack and understand the French Language
• patient not affilated to the French healthcare system
• pregnancy