Fecal or bowel incontinence is the loss of normal control over bowel movements, causing stool to be unexpectedly released from the rectum. This problem affects as many as five million people in the United States. Bowel incontinence is more common in women than men and can range from a small leakage of stool while passing gas to complete loss of bowel control.

Causes of fecal or bowel incontinence

There are many causes of fecal incontinence. The condition occurs when something is wrong within the complex mechanisms of the body that maintain continence. Continence depends on functioning muscles and nerves in and around the rectum and anal canal.

Common causes of fecal incontinence include diarrhea, pelvic floor dysfunction, muscle and nerve damage, loss of storage capacity and constipation.

Diarrhea, or loose stool, may be associated with a feeling of urgency or stool leakage due to the frequent liquid stools passing through the anal opening. Diarrhea is more difficult to control than solid stool and even people who do not suffer from fecal incontinence can have an accident when they have diarrhea.

Pelvic floor dysfunction - the pelvic floor plays an important role in maintaining continence and abnormalities of the pelvic floor can lead to bowel incontinence. Such dysfunction are: decreased perception of rectal sensation, decreased anal canal pressures, decreased squeeze pressure of the anal canal, impaired anal sensation, a dropping down of the rectum (rectal prolapse) and protrusion of the rectum through the vagina (rectocele). The cause of pelvic floor dysfunction is often caused by childbirth.

Muscle damage - bowel incontinence is most often caused by injury to one or both of the ring-like muscles at the end of the rectum called the anal sphincters. The sphincters keep stool inside. When damaged, the muscles are not strong enough to do their job, and stool can leak out. In women, the damage often happens when giving birth. Anal operations or injury to the tissue surrounding the anal region can damage the anal muscles and hinder bowel control.

Nerve damage - fecal incontinence can be caused by damage to the nerves that control the anal sphincters or to the nerves that sense stool in the rectum. If the nerves that control the sphincters are injured, the muscle does not work properly and incontinence can occur. Nerve damage can be caused by childbirth, a long-term habit of straining to pass stool, stroke, and diseases that affect the nerves, such as diabetes and multiple sclerosis.

Loss of storage capacity - 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 cannot stretch as much to hold stool, resulting in incontinence.

Constipation is one of the most common causes of fecal incontinence and can lead to a large amount of stool in the rectum, a condition called fecal impaction. A fecal impaction is a large mass of dry, hard stool that interferes with normal ability to control bowel movements. A watery stool from higher in the bowel may eventually move around the impaction and leak out.