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Bowel Incontinence

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Causes of Bowel Incontinence

Bowel incontinence can have several causes:

• Constipation - Constipation is one of the most common causes of bowel incontinence. Constipation causes large, hard stools to become lodged in the rectum. Watery stool can then leak out around the hardened stool. Constipation also causes the muscles of the rectum to stretch, which weakens the muscles so they can't hold stool in the rectum long enough for a person to reach a bathroom.

• Damage to the Anal Sphincter Muscles - Muscle Damage - Bowel incontinence can be caused by injury to one or both of the ring-like muscles at the end of the rectum called the anal internal and external sphincters. The sphincters keep stool inside. When damaged, the muscles aren't strong enough to do their job and stool can leak out. In women, the damage often happens when giving birth. The risk of injury is greatest if the doctor uses forceps to help deliver the baby or performs an episiotomy, which is a cut in the vaginal area to prevent it from tearing during birth. Hemorrhoid surgery can also damage the sphincters.
• Damage to the Nerves of the Anal Sphincter Muscles or the Rectum - Nerve Damage - Bowel incontinence can be caused by damage to the nerves that control the anal sphincters or the nerves that sense stool in the rectum. If the nerves that control the sphincters are injured, the muscles don't work properly and incontinence can occur. If the sensory nerves are damaged, they don't sense that stool is in the rectum so you won't feel the need to use the bathroom until stool has leaked out. Nerve damage can be caused by childbirth, a long-term habit of straining to pass stool, stroke, physical disability due to injury, and diseases that affect the nerves such as diabetes and multiple sclerosis.
• Loss of Storage Capacity in the Rectum - Normally, the rectum stretches to hold stool until you can get to a bathroom. But rectal surgery, radiation treatment, and inflammatory bowel disease can cause scarring that makes the walls of the rectum stiff and less elastic. The rectum then can't stretch as much to hold stool and bowel incontinence results. Inflammatory bowel disease also can irritate rectal walls, making them unable to contain stool.
• Diarrhea - Diarrhea, or loose stool, is more difficult to control than solid stool because with diarrhea the rectum fills with stool at a faster rate. Even people who don't have bowel incontinence can leak stool when they have diarrhea.
• Pelvic Floor Dysfunction - Abnormalities of the pelvic floor muscles and nerves can cause bowel incontinence. Examples include:
  • Impaired ability to sense stool in the rectum
  • Decreased ability to contract muscles in the anal canal to defecate
  • Dropping down of the rectum, a condition called rectal prolapse
  • Protrusion of the rectum through the vagina, a condition called rectocele
  • General weakness and sagging of the pelvic floor

Childbirth is often the cause of pelvic floor dysfunction, and incontinence usually doesn't appear until the midforties or later.

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References:
National Digestive Diseases Information Clearinghouse (NDDIC)
July 2007
digestive.niddk.nih.gov

The information discussed above is a general overview and does not include all the facts, or include everything there is to know about any medicine and/or products mentioned. Do not use any medicine and/or products without first talking to your doctor. Possible side effects of medications, other than those listed, may occur. Other brand names or generic forms of this medicine may also be available. If you have questions or concerns, or want more information, your doctor or pharmacist has the complete prescribing information about this medicine and possible drug interactions.