Fecal Incontinence

Causes

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Sphincter muscles, external and internal, in your anus — a short canal at the end of the rectum  — control the release of waste (stool) from the body. As the rectal walls stretch, they signal the need to release stool. As the sphincter muscles relax, the rectal walls contract to increase pressure. Sometimes, the abdominal muscles contract to put pressure on the outside of the colon and rectum. With this coordination of muscles and also nerves, stool is expelled through the anus.

The ability to hold stool requires the normal function of the rectum, anus and nervous system. In addition, people must have the physical and mental capabilities to recognize and appropriately respond to the urge to defecate. If something is wrong with any factor, fecal incontinence can occur.

Numerous conditions and disorders can cause fecal incontinence, including:

Constipation. Chronic constipation may lead to impacted stool  — a large mass of dry, hard stool within your rectum. This mass can be too large to pass; as a result, the muscles of the rectum and intestines stretch, and then eventually weaken. Watery stool from farther up the digestive system may move around the hard mass and leak, causing fecal incontinence. Chronic constipation may also make the nerves of the anus and rectum less responsive to the presence of stool in the rectum.

Diarrhea. Solid stool is easier to retain in the rectum than loose stool, so the loose stools of diarrhea can cause or worsen fecal incontinence.

Muscle damage. If the anal sphincter muscles are damaged, they may not be able to hold back stool properly. This damage can occur during childbirth, especially with an episiotomy or if forceps are used during delivery.

Nerve damage. The nerves that control the anal sphincter or those that sense stool in the rectum can be damaged by childbirth, constant straining when having a bowel movement, spinal cord injury, stroke, and diseases such as diabetes and multiple sclerosis.

Loss of storage capacity. If the rectum is scarred or the rectal walls are stiffened from surgery, radiation treatment or inflammatory bowel disease, the rectum can't stretch adequately, so excess stool leaks out.

Surgery. Surgery to treat hemorrhoids also can cause damage to the anus and result in fecal incontinence, as can more complex operations involving the rectum and anus.

Other conditions. If the rectum drops down into the anus (rectal prolapse) or, in women, if the rectum protrudes through the vagina (rectocele), fecal incontinence can result. Hemorrhoids may prevent complete closure of the anal sphincter, leading to fecal incontinence.

Aging. Over time, muscles and ligaments that support your pelvis, as well as your anal sphincter muscles, can weaken, leading to incontinence.

Chronic laxative abuse. Relying on laxatives to maintain regularity can lead to incontinence.