Physiology: evacuation, pelvic floor and continence mechanisms

Faecal continence is defined by the ability to perceive, retain and evacuate bowel contents at socially convenient times. This is reliant upon normal function of the main involved organs (i.e. rectum, pelvic floor and anal sphincters) together with their associated sensorineural pathways. Incontinence may occur as a result of dysfunction in any one of these systems or due to factors such as systemic disease, emotion, bowel motility and stool consistency. The act of defaecation is a conscious process that involves interplay between motor and sensory elements, initiated by higher cortical function.Incontinence and evacuatory dysfunction are investigated using specialized tests that assess sphincter function and structure (anorectal manometry, endoanal ultrasound), anorectal and pelvic floor function (defaecating proctography, nerve conduction studies) and luminal integrity and colonic function (transit studies and endoscopy).