Subject older than 18 years Absence of anorectal symptoms (no constipation, no fecal incontinence) Absence of pelvic floor disorders Vaizey score = 0 Kess score < 9 Subject with health insurance Written informed consent Non inclusion criteria: Patient younger than 18 years Pregnancy Incapability to give consent No written informed consent Participation to another study at the same time Previous ano-rectal surgery Pelvic radiotherapy Neurological disorder Diabetes mellitus