Bowel incontinence (fecal incontinence) definition
Fecal incontinence can be defined as the unintentional loss of stool (feces)
or gas (flatus). It is often due to a failure of one or more of the components
that allow the body to control the evacuation of feces, when it is socially
A normal bowel movement requires a complex interaction and feedback system
between the nerves and muscles of the rectum and anus. The anatomy of this area
is complicated. The rectum is a reservoir for holding stool. Two sphincters or
circular muscles separate the rectum from the anus and control when the anus
should allow a bowel movement. The internal anal sphincter (IAS) is under
involuntary control of the body's nervous system, while the external anal
sphincter (EAS) can be actively controlled by the indivdiual. In addition, the puborectalis muscle tugs at the junction of the rectum and anus, creating a 90
degree angle, which makes it harder for stool to move involuntarily into the
When the rectum is full and for a normal bowel movement to occur, the IAS
relaxes just a little. Cells in the anus can detect feces or flatus and if the
brain says that it is an opportune social time to pass gas or have a bowel
movement, the puborectalis muscle relaxes, straightening the path from the
rectum to the anus. Squatting or sitting helps increase the pressure within the
abdomen, and muscles that surround the rectum squeeze its contents, the EAS
relaxes and a bowel movement occurs.
If it is not an appropriate time to open the bowel, the puborectalis muscle
contracts, the EAS contracts, the rectum relaxes and stool is forced back into
the upper part of the rectum, causing the urge to have a bowel movement to be
What causes bowel incontinence?
Fecal incontinence occurs because of an underlying disease or illness (it is
not considered a "disease"). There are numerous potential causes and many
patients have more than one reason to cause loss of bowel control.
Damage to muscles and nerves may occur directly at the time of
childbirth or after anal or rectal surgery.
Neurologic diseases such as stroke,
spinal cord injury, and
spina bifida can be potential causes of fecal incontinence. Complications of
diabetes can also cause
peripheral nerve damage leading to incontinence.
Patients with inflammatory bowel disease (Crohn's disease,
ulcerative colitis) and irritable bowel disease may develop fecal incontinence.
Stool seepage is different than fecal incontinence. Minor staining can occur
in people who have hemorrhoids, rectal fistula, rectal prolapse and poor hygiene.
Other causes include
chronic diarrhea, parasite infections, and laxative abuse.
Paradoxical diarrhea or overflow incontinence may occur is a a person who has
constipation. In paradoxical diarrhea, stool fills the rectum, hardens and becomes impacted.
Liquid stool leaks around the fecal mass, imitating incontinence.
Reviewed on 6/13/2013
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