Faecal continence is the ability to perceive, retain, and evacuate rectal contents at a time and place of choice. Faecal incontinence is defined as any loss of faecal continence after the age of four years. The main pathophysiological mechanisms are impairment of sphincter contraction and decreased sensitivity of the rectum in response to distension with stool.
Diseases of the CNS as well as colonic diseases are responsible for faecal incontinence:
- Diseases of the CNS: stroke, MS, dementia, spinal cord transsection, and loss of consciousness. All these diseases either affect the ability to contract the external sphincter or decrease the sensation of a full rectum.
- Decreased cognition (due to dementia: not able to find the toilet)
- Poor mobility: elderly that cannot walk well are not able to reach the toilet in time and thus become incontinent.
- Colonic diseases: severe diarrhoea and inflammatory bowel disease: in case of diarrhoea, the external anal sphincter can only ensure continence against a vigorously propelling colon for a short time. In IBD, the compliance of the rectum may be reduced, resulting in the rectum storing abnormal quantities of stool.
- Sphincter incompetence: e.g. due to radiotherapy of the rectum in prostate cancer.
- Antimicrobials also destroy the bacteria in the GI tract. Excessive use of laxatives can cause faecal incontinence. Other drugs (chemotherapy) have colonic toxicities.
Faecal incontinence can be due to the inability to contract the internal rectal sphincter.
Extra info: It occurs when the external sphincter cannot contract.