Fecal Incontinence: Description & Anatomy

Fecal incontinence is the unintended passage of stool. Both men and women may experience such leakage, but it is more common in women, particularly those who have given birth. For both men and women, the incidence of fecal incontinence increases with age, as connective tissues and muscles of the pelvic floor weaken.

For a long time, experts could only guess at how often this condition affected men and women. But for the first time, national statistics have been collected, at least for women, by the National Center for Health Statistics. A survey of 1,961 women, published in 2008, found that at least 9% of women experience the unintended leakage of stool at least once a month.

If you have fecal incontinence, you may not be able to hold in your stool long enough to reach the bathroom. Or you might experience unexpected leakage of stool when you haven’t felt any urge (see Figure 8). The symptoms of fecal incontinence can range from mild occasional leakage of liquid stool to a daily debilitating condition with consequences for self-confidence, self-image, and the ability to maintain friendships or careers. Most people with fecal incontinence don’t tell their friends, families, or even their doctors. Instead, they limit their activities to avoid accidents and embarrassment. This can result in isolation and depression.

Because people are reluctant to seek help, fecal incontinence is sometimes perceived as rare. This perception is wrong. Fecal incontinence occurs in adults of all ages, and for older or disabled people, it is a leading reason for nursing home placement. One survey found that nearly half of nursing home residents had fecal incontinence.

Fecal incontinence often goes hand in hand with urinary incontinence. Even though they may not disclose it readily, many people with urinary incontinence have fecal incontinence as well.

Most people with fecal incontinence can be helped. If you or someone you know is experiencing fecal incontinence, seek medical advice. There are new options for evaluating, treating, and managing this distressing condition, and even if your previous attempts to get help have been unsatisfactory, you may be able to get help now. While available treatments may not completely cure fecal incontinence, they can lead to gradual improvements that increase quality of life and allow a patient to participate more fully in daily activities.

Figure 8: Causes of fecal incontinence

Causes of fecal incontinence

Surgery, constipation, radiation treatments, childbirth in women, and other causes contribute to fecal incontinence. For example, surgery may cause damage to pelvic floor muscles (A) or pudendal nerves (B). Chronic diarrhea or constipation can damage the rectum (C). Childbirth or surgery can damage the anal sphincters (D).

Anatomy of fecal continence

You rely on your digestive system to process the food you eat. The system absorbs vital nutrients into the bloodstream, and then removes the remaining waste products and indigestible food components from your body. By the time food has traveled through your digestive tract to your large intestine, or colon, it is made up of waste material, which continues to lose water and solidify as it slowly moves along. The final product is known as stool, or feces.

At the end of your digestive tract are two areas crucial to fecal continence: the rectum and the anal canal. Muscles in the colon propel feces into the rectum, which has walls that stretch to hold the stool. The last inch of the rectum is called the anal canal. Two kinds of muscle surround it. The internal anal sphincter, which is not under your conscious control, stays contracted most of the time to prevent leakage. The external anal sphincter surrounds the internal anal sphincter.

How does your body know when to release stool? You have stretch-detecting nerve endings in the rectum. When your nerves detect that the rectum is full, the internal sphincter opens briefly and lets a tiny bit of the rectum’s contents come in contact with the external sphincter, which is rich with nerve endings. In a rapid “sampling reflex,” these nerves inform the brain about whether the rectal contents are intestinal gas or liquid or solid stool. This allows you to act accordingly. You might allow gas to escape, or look for a bathroom right away if you have diarrhea. Otherwise, you might decide whether it is convenient to have a bowel movement, or whether you want to wait for a better time or place.

To delay, you tighten the external anal sphincter (usually without thinking about it) to hold feces inside. As you are attempting to hold in stool, you also contract the puborectalis muscle, a pelvic floor muscle that loops around the rectum. When this muscle is contracted, it pulls the rectum so that it lies at a 90-degree angle to the anal canal rather than more directly above it. This counters the pull of gravity. Contracting these muscles often curbs the urge to defecate. The urge returns when more feces enter the rectum.

Once you are in the bathroom, you relax the puborectalis muscle and both the internal and external sphincters. Then, to propel the stool downward, you increase pressure in the abdominal cavity through the Valsalva or “bearing down” maneuver — closing off the airway, tightening the abdominal muscles, and pushing the diaphragm down.

 

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