This innovative project aims to investigate structures and morphology of the external anal sphincter (EAS) as well as the impact of sacral neuromodulation (SNM) on the EAS morphology and biochemistry among patients with faecal incontinence (FI). SNM is a well implemented treatment for FI and consist of electrical stimulation of sacral nerve roots to promote continence and may even contribute to total continence. It has shown a positive effects on both short- and long-term. The biologic effect of SNM on EAS is unknown. The aim is to investigate the effect of SNM on EAS morphology, function, and biochemistry to help physicians and researchers to understand the underlying mechanisms of SNM and the anal sphincter complex to further improve and optimize treatment methods for patients with FI. The research project consists of three phases. The first phase includes biopsies from the EAS among patients with no previous history of FI. These patients have been diagnosed with rectal cancer and will undergo surgery with abdominoperineal excision. The second phase includes patients diagnosed with FI and subject for implantation of SNM for treatment of FI. Prior to implantation of SNM all patients will have been examined with 3D endo-anal ultrasound and anorectal manometry as well as answered questionnaires targeting general health, bowel dysfunction and FI. A biopsy of the superficial portion of the EAS is retrieved under local anaesthesia in connection to the test period for implantation of the SNM device. The last phase, phase three, includes 3D endo-anal ultrasound, anorectal manometry, and a second biopsy of the EAS twelve months after implantation with SNM. The histopathological analysis in all the three phases will include general morphology, distribution of cell nuclei, satellite cells, muscle fiber type, neural structures and connective tissue.