Constipation

 | January 1, 2008

Constipation

Constipation is the slow movement of feces through the large intestine, resulting in the difficult passage of dry, hard stool. It's one of the most common gastrointestinal complaints in the United States, responsible for more than 2.5 million visits to health providers each year. The National Institutes of Health says that more than four million Americans have frequent constipation. Constipation is more common in women than men, and more common among older people. Americans spend around $725 million on laxatives each year.

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How constipation happens

The hard, dry stool that defines constipation develops when the colon absorbs too much water. This may happen because the muscle contractions of the colon are too slow, so the stool moves along sluggishly. Or it can occur when the anal sphincter fails to relax when it should, causing an excessive amount of stool to be stored in the rectum. Constipation can also occur when you consciously slow the movement of stool through the colon to hold back a bowel movement. If you routinely override the urge to defecate by consciously constricting the external sphincter muscles that surround the anus, your reflex to defecate may be blunted, and accumulated stool may harden as a result, becoming even more difficult to pass.

Eventually, the colon tries to move the stool by squeezing down to try and push it. This causes an uncomfortable pressure and cramping. If the stool is not eliminated, more hard stool accumulates. When the stool finally passes, it can cause extreme discomfort.

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Frequency of bowel movements: What's normal?

What is regularity? It's not a medical concept, but a myth that you've got to move your bowels each day to be healthy. In fact, as far back as 1909, the British physiologist Sir Arthur Hurst said it wasn't unusual to find healthy people who had a bowel movement three times a day or once every three days. Today, that's still the range that's considered "normal." But many perfectly healthy people don't even fall within this broad range. In 1813, the British physician William Heberden described a patient who "never went but once a month." He also described a patient who relieved himself 12 times a day. Both patients seemed perfectly content with their bowel habits.

The truth is that everyone experiences variations in how often they move their bowels. Menstruation, vigorous physical exercise, diet, travel, and stress can all cause temporary changes in bowel habits. Going a day without a bowel movement certainly shouldn't be considered constipation. And three movements in a day isn't necessarily diarrhea. More important than the number of bowel movements is the consistency of the stools as they pass, the effort needed to expel them, any associated symptoms, and changes in frequency.

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Causes of constipation

There are many factors that may predispose someone to constipation. Some can easily be prevented by changing habits and lifestyle (although the role of lifestyle factors in constipation may not be as important as once thought). Often, the cause has to do with physiological problems or diseases. Following are the more common causes of constipation:

Lack of exercise. People who exercise regularly seldom complain about constipation. Basically, the colon responds to activity. Good muscle tone in general is important to regular bowel movements. The abdominal wall muscles and the diaphragm all play a crucial role in the process of defecation. If these muscles are weak, they're not going to be able to do the job as well. But exercise is not a cure-all. Increasing exercise to improve constipation may be more effective in older people, who tend to be more sedentary, than in younger people.

Medications. Constipation is a side effect of many prescription and over-the-counter drugs. These include pain medications (especially narcotics), antacids that contain aluminum, antispasmodics, antidepressants, tranquilizers and sedatives, bismuth salts, iron supplements, diuretics, anticholinergics, calcium-channel blockers, and anticonvulsants.

Irritable bowel syndrome (IBS). Some people who suffer from IBS (see "Irritable bowel syndrome") have sluggish bowel movements, straining during bowel movements, and abdominal discomfort. Constipation may be the predominant symptom, or it may alternate with diarrhea; cramping, gas, and bloating are also common.

Abuse of laxatives. People who use laxatives for a long time often come to rely on them for both psychological and physiological reasons. The colon may begin to require laxatives to spur bowel movements. In the past, laxatives were thought to damage nerve cells in the colon and interfere with the colon's innate ability to contract. However, newer formulations of laxatives have made this outcome rare (see "Oral laxatives").

Changes in life or routine. Pregnancy, for example, may cause women to become constipated because of hormonal changes or because the heavy uterus pushes on the intestine. Aging often affects regularity because a slower metabolism can reduce intestinal activity and muscle tone. Traveling can give some people problems because it changes normal diet and daily routines.

Ignoring the urge. If you have to go, go. If you hold in a bowel movement, for whatever reason, you may be inviting a bout of constipation. People who repeatedly ignore the urge to move their bowels may eventually stop feeling the urge.

Not enough fiber and liquid in the diet. A diet too low in fiber and liquid and too high in fats can contribute to constipation. Fiber absorbs water and causes stools to be larger, softer, and easier to pass. Increasing fiber intake helps cure constipation in many patients, but those with more severe constipation sometimes find that increasing fiber makes their constipation worse and leads to gassiness and discomfort.

Other causes of constipation. Diseases that can cause constipation include neurological disorders, such as Parkinson's disease, spinal cord injury, stroke, or multiple sclerosis; metabolic and endocrine disorders, such as hypothyroidism, diabetes, or long-term kidney disease; bowel cancer; and diverticulitis (see "Diverticular disease"). A number of systemic conditions, like scleroderma, can also cause constipation. In addition, intestinal obstructions, caused by scar tissue (adhesions) from an operation or strictures of the colon or rectum, can compress, squeeze, or narrow the intestine and rectum, causing constipation.

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Functional constipation

In rare cases, people experience constipation that persists for years or decades, even though they have no physical abnormality of the bowel on x-ray studies (such as barium enema examinations) or colonoscopy. This condition — known as chronic severe constipation, functional constipation, or chronic idiopathic constipation — is rare, but is more common in women.

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Diagnosing constipation

Diagnosing constipation might sound simple, but in order to determine what's causing the problem — particularly if it persists — your doctor will need to ask questions about your health and symptoms and perform a physical exam. He or she will ask what medications you are taking, in case one of them could be contributing to the problem.

The physical exam may involve a visual and hands-on examination of your abdomen for any masses or tenderness. Your doctor may also perform a digital rectal exam (insertion of a gloved finger into the rectum) to feel for polyps or other abnormalities and to assess the strength of the anal sphincter muscle. He or she may perform one of several tests to help determine if there's a blockage in the colon or an underlying condition such as hypothyroidism.

Among the tests your doctor might order are a fecal occult blood test (FOBT), to determine if there's blood in the stool, or a barium enema and a sigmoidoscopy to look for abnormalities. Patients with functional constipation may need special tests, including a colonic transit study (to measure how quickly stool passes through the colon), defecography (an x-ray of the rectum as barium paste is eliminated), and anorectal manometry (to measure the pressure of anal contraction).

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Treating constipation

People suffering from constipation may try a number of measures, including boosting fiber and fluid intake and increasing physical exercise. Drinking more fluids may reduce the need for the colon to rehydrate stools and is, in any case, harmless. Exercise, which is widely believed to promote regularity (although few studies have investigated this), has many other health benefits as well.

Bowel training is another option. In order to retrain your bowel, you attempt to defecate at a regular time each day, when bowel movements are most likely to occur (first thing in the morning, following exercise, or after a meal, for example). The idea is to repeat the routine until the body adopts the bowel movement as part of its daily rhythm. Although bowel training is harmless and does help some people, it has not been widely tested.

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Increasing fiber

For many people, adding fiber to the diet is a highly effective way to prevent or treat constipation. The Food and Nutrition Board of the Institute of Medicine recommends 38 grams of fiber per day for men and 25 grams per day for women ages 50 and younger; for men and women over 50, they recommend 30 and 21 grams per day, respectively. Most Americans ingest much less fiber than these amounts.

Whole-grain foods, brans, and fruits and vegetables are a good source of fiber. Fiber will also speed gastrointestinal transit in people whose movement is slow. At least 20 grams per day of unprocessed bran and plenty of liquid are necessary to provide these benefits. Depending on the brand, a bowl of bran cereal delivers approximately 4 to 12 grams of fiber.

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Laxatives

Under most circumstances, laxatives should be used only when dietary and behavioral measures fail. Stimulant laxatives contain chemicals that act directly on the intestine to increase its secretion of water. Some of them also elicit more vigorous contractions from the colon.

One of the newest FDA-approved prescription drug to treat functional constipation is the laxative lubiprostone (Amitiza). This chloride-channel agonist increases the secretion of fluid into the intestine, which eases the passage of stool through this area. Lubiprostone may be a good option for people who are not helped by standard treatments. Nausea was a common side effect in clinical trials.

Suppositories. Suppositories have been used to aid evacuation since the days of ancient Egypt, Greece, and Rome. Glycerin suppositories are made of about 70% glycerin, sometimes with sodium stearate (a fatty acid) added. When inserted, a glycerin suppository stimulates the reflex to defecate, in part because of its lubricating action. Suppositories with bisacodyl (Dulcolax) are more potent and usually produce a bowel movement within 20 minutes.

Enemas. Enemas are used primarily when oral laxatives don't work. The simple tap water enema distends the rectum, mimicking its natural distension by the stool and prompts the reflex by which the rectum empties itself as the sphincters open. While it isn't ideal to rely on artificial stimulation to kick off evacuation, an enema is probably the most benign way of doing so. Sodium phosphate (Fleet) enemas are available in single-dose plastic containers. These salts draw fluid into the bowel, prompting contraction. Oil-containing enemas are sometimes prescribed as softeners for feces that have become hardened within the rectum. They are generally recommended for short-term use only. Avoid soapsuds enemas, which can irritate the lining of the colon.

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Medications for constipation

Large clinical trials have found that compared with placebo, tegaserod (Zelnorm) significantly increases the number of bowel movements and improves symptoms of constipation, including abdominal discomfort and pain, bloating and distension, straining, and stool consistency. But it is available only to some women with IBS or functional constipation who are in critical need of the medication. These women must be younger than age 55 and have no known heart problems.

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Surgery

Surgical intervention as a means of treating severe constipation has fallen far out of favor because of dismal results. The operation involved surgically removing the colon and connecting the small intestine directly to the rectum. But at least half of those undergoing the procedure have had to endure further surgery because of obstructions of the small intestine.

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Alternative approaches

If increased fiber, liquids, and exercise are insufficient, a variety of alternative approaches are available. Solid scientific evidence for these methods is limited, but some people find flaxseed or sesame seed useful. Others have reported success using massage, acupressure, or biofeedback. Biofeedback can be helpful for severe constipation caused by dysfunction of the anal sphincter and pelvic floor muscles.

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Review Date: 2008-01-01

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