Why does fecal incontinence occur?
Bowel function is controlled by 3 things: anal sphincter pressure, rectal sensation and rectal storage capacity. The anal sphincter is a muscle that contracts to prevent stool from leaving the rectum. This muscle is critical in maintaining continence. Rectal sensation tells a person that stool is in the rectum and that it is time to go to the bathroom. The rectum can stretch and hold stool for some time after a person becomes aware that the stool is there. This is the rectal storage capacity.
A person also must be alert enough to notice the rectal sensation and do something about it. He or she must also be able to move to a toilet. If something is wrong with any of these factors, then fecal incontinence can occur.
What causes fecal incontinence?
Muscle damage is involved in most cases of fecal incontinence. In women, this damage commonly occurs during childbirth. It's especially likely to happen in a difficult delivery that uses forceps or an episiotomy. An episiotomy is when a cut is made to enlarge the opening to the vagina before delivery. Muscle damage can also occur during rectal surgery, such as surgery for hemorrhoids. It may also occur in people who have inflammatory bowel disease or a perirectal abscess.
People can often compensate for muscle weakness. Typically, incontinence develops later in life when muscles weaken and the supporting structures in the pelvis become loose.
Damage to the nerves that control the anal muscle or regulate rectal sensation is also a common cause of fecal incontinence. Nerve injury can occur in the following situations:
- During childbirth.
- With severe and prolonged straining for stool.
- With diseases such as diabetes, spinal cord tumors and multiple sclerosis.
Fecal incontinence may also be caused by a reduction in the elasticity of the rectum, which shortens the time between the sensation of the stool and the urgent need to have a bowel movement. Surgery or radiation injury can scar and stiffen the rectum. Inflammatory bowel disease can also make the rectum less elastic.
Because diarrhea is more difficult to control than formed stool, it is an added stress that can lead to fecal incontinence.
Written by familydoctor.org editorial staff