Digestive Basics - Constipation

Part 2: What causes constipation?

What causes constipation? (continued from page 1)

Some people with IBS, also known as spastic colon, have spasms in the colon that affect bowel movements. Constipation and diarrhea often alternate, and abdominal cramping, gassiness, and bloating are other common complaints. Although IBS can produce lifelong symptoms, it is not a life-threatening condition. It often worsens with stress, but there is no specific cause or anything unusual that the doctor can see in the colon.

During pregnancy, women may be constipated because of hormonal changes or because the heavy uterus compresses the intestine. Aging may also affect bowel regularity because a slower metabolism results in less intestinal activity and muscle tone. In addition, people often become constipated when traveling because their normal diet and daily routines are disrupted.

Myths about constipation have led to a serious abuse of laxatives. This is common among older adults who are preoccupied with having a daily bowel movement.

Laxatives usually are not necessary and can be habit-forming. The colon begins to rely on laxatives to bring on bowel movements. Over time, laxatives can damage nerve cells in the colon and interfere with the colon's natural ability to contract. For the same reason, regular use of enemas can also lead to a loss of normal bowel function.

People who ignore the urge to have a bowel movement may eventually stop feeling the urge, which can lead to constipation. Some people delay having a bowel movement because they do not want to use toilets outside the home. Others ignore the urge because of emotional stress or because they are too busy. Children may postpone having a bowel movement because of stressful toilet training or because they do not want to interrupt their play.

Diseases that cause constipation include neurological disorders, metabolic and endocrine disorders, and systemic conditions that affect organ systems. These disorders can slow the movement of stool through the colon, rectum, or anus.

Neurological disorders:

Metabolic and endocrine conditions:

Systemic disorders:

Intestinal obstruction, scar tissue (adhesions), diverticulosis, tumors, colorectal stricture, Hirschsprung's disease, or cancer can compress, squeeze, or narrow the intestine and rectum and cause constipation.

Some people have chronic constipation that does not respond to standard treatment. This rare condition, known as idiopathic (of unknown origin) chronic constipation may be related to problems with intestinal function such as problems with hormonal control or with nerves and muscles in the colon, rectum, or anus. Functional constipation occurs in both children and adults and is most common in women.

Colonic inertia and delayed transit are two types of functional constipation caused by decreased muscle activity in the colon. These syndromes may affect the entire colon or may be confined to the lower or sigmoid colon.

Functional constipation that stems from abnormalities in the structure of the anus and rectum is known as anorectal dysfunction, or anismus. These abnormalities result in an inability to relax the rectal and anal muscles that allow stool to exit.

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