Neurophysiological Mechanism in Sacral Neuromodulation in Patients Suffering From Fecal Incontinence

Fecal continence is maintained by several mechanisms including anatomical factors, anorectal sensation, rectal compliance, stool consistency, anal muscle strength, mobility, and psychological factors. The homeostatic balance is easily disturbed by functional or structural anorectal disturbances that may coexist. Common anorectal disorders are fecal incontinence, functional anorectal pain, and functional defecation disorders. These conditions greatly affect life quality for the patients. Current technologies for anorectal functional assessment studies have limitations and often overlap is found between patient groups with lack of correlation between measurements and symptoms. Defecation physiology has been studied for many years but the mechanics and mechanosensation of defecation are still not well understood.

Fecobionics combines several existing tests to provide novel insight into anorectal function. The purpose for the development of Fecobionics was to overcome the technological controversies and disagreement between various tests and unphysiological test conditions. The aim was to imitate defecation as close as possible to the natural process. Fecobionics was developed to simulate stool and to provide the driving pressure and resulting deformations of stool along with a measure of an objective anorectal angle during defecation in a single examination. Fecobionics makes it possible to describe objectively, without disturbing the defecation process, the opening characteristics and pressure signatures during initial entry into the relaxing anal canal as well as other parameters

The overall goal is to provide mechanistic understanding of defecation in health and defecatory disorders. Fecobionics exceeds previous attempts to make artificial stool for evaluation of defecation and integrates other technologies as well. It was designed to have a consistency and deformability of Type 4 (range type 3-5) on the Bristol stool form scale. The range from types 3-5 is found in 70% of healthy subjects. A major novelty is that Fecobionics measures pressures in axial direction; i.e., in the flow direction. It is anticipated that Fecobionics will shed light on the neurophysiology of defecation in health and disease, including understanding the effect of biofeedback and neuromodulatory effect of SNS. It will be of great value to provide endpoints in normal subjects that in future studies can be objective measures for monitoring treatment efficacy. The present protocol is on normal subjects only, i.e. studying mechanisms of defecation.