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. 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.

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 push it along. 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.

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.


Causes of constipation

There are many factors that 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. The 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 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. Laxatives are sometimes used inappropriately, for example, by people suffering from anorexia nervosa or bulimia. But for people with long-term constipation, the extended use of laxatives may be a reasonable solution and safe when used properly.

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. 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.


Functional constipation

Some 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.

Do you have functional constipation?

The Rome III criteria for a diagnosis of functional constipation state that patients must have experienced two or more of the following symptoms for the past three months, and that symptoms must have begun at least six months before diagnosis:

  • straining during at least one out of four bowel movements
  • having lumpy or hard stools during at least one out of four bowel movements
  • having a sensation of incomplete evacuation in at least one out of four bowel movements
  • having a sensation that your rectum or anus is blocked during at least one out of four bowel movements
  • resorting to manual maneuvers such as using a finger to help facilitate movement during at least one out of four bowel movements
  • fewer than three defecations a week.

The diagnosis also requires these two conditions:

  • loose stools rarely present without the use of a laxative
  • no diagnosis of irritable bowel syndrome.


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.

Evaluating constipation may require special tests, including a colonic transit study (to measure how quickly stool passes through the colon), defecography (an imaging study of the rectum during attempted defecation), and anorectal manometry (to measure the pressure of anal contraction).


Treating constipation

People suffering from constipation should start by 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.


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, fruits, and vegetables are good sources of fiber. Fiber will generally improve symptoms of mild constipation in people whose diet does not include adequate amounts. 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 high-fiber bran cereal delivers approximately 4 to 12 grams of fiber.

Fiber supplements and other products containing psyllium seed or methylcellulose are quite effective. Follow the directions on the label carefully as you mix the powder with a large glass of water or juice. Drinking plenty of liquid is most important when using these products. Some people find that drinking a second glass of water or juice after drinking the mixture boosts effectiveness. If liquid formulations are difficult for you to ingest, psyllium is also available in capsule form.



For thousands of years, people have been using various substances to help ease the passage of stool through the bowel. Under most circumstances, laxatives should be used only when dietary and behavioral measures fail. Stimulant laxatives act directly on the intestine to elicit more vigorous contractions of the colon and increase secretion of water in the intestine.

Oral laxatives

Depending on the type, oral laxatives work in a variety of ways to ease the passage of stool through the rectum.

Bulk-forming agents. These fiber-based products take a day or so to work but are very effective and safe to take indefinitely on a daily basis. Take with plenty of liquid.

  • bran (in food and supplements)
  • calcium polycarbophil (e.g., FiberCon)
  • methylcellulose (Citrucel and others)
  • psyllium (Metamucil and other brands)

Stool softeners merge with feces and soften consistency.

  • docusate (Colace, Surfak, others)—generally safe for long-term use
  • mineral oil—avoid daily use because it reduces absorption of fat-soluble vitamins and can cause lung damage if accidentally inhaled

Osmotic agents are salts or carbohydrates that promote secretion of water into the colon. They are reasonably safe, even with prolonged use.

  • polyethylene glycol (Miralax)—shown to be helpful in children with functional constipation.

Saline laxatives attract and retain water in the intestines, increasing pressure and release of stool.

  • Magnesium (Milk of Magnesia, Epsom Salt)

Stimulant laxatives act directly on the intestinal lining to alter water and electrolyte secretion.

They’re best used for occasional constipation.

  • bisacodyl (Dulcolax, Ex-Lax Ultra, Correctol, and others)
  • casanthranol (included in Dialose Plus, Peri-Colace)
  • cascara (included in Naturalax)
  • castor oil (Purge)
  • senna (Ex-Lax, Fletcher’s Castoria, Senokot, others)

A unique side effect of some stimulant laxatives, those in the class known as anthraquinones (casanthranol, cascara, senna), is pseudomelanosis coli—a blackening of the lining of the colon seen on colonoscopy. However, pseudomelanosis coli is not associated with altered colon function and appears to be a harmless consequence of long-term stimulant laxative use.

Chloride-channel agonists were approved in January 2006; their long-term effects are unknown. They cause additional fluid to be secreted into the intestine, making it easier to pass stool.

  • lubiprostone (Amitiza)

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. 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, occasional use can be safe and effective. 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.

Chloride-channel agonists. One prescription drug FDA-approved to treat functional constipation is 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.



Biofeedback can be helpful for severe constipation caused by ineffective rectal emptying that results from an inability to relax the necessary muscles and adequately straighten the angle of the rectum enough to pass stool effectively. With this method, you can be trained to relax the pelvic floor muscles during straining and coordinate this action with abdominal wall muscle contractions to enable the passing of stool. About two-thirds of patients with anorectal dysfunction report improvement.


Probiotics and prebiotics

Probiotics are live microorganisms used to benefit health. Prebiotics are non-living substances intended to promote the growth of beneficial organisms. A variety of probiotic and prebiotic agents have been tested for treatment of constipation, with varying results. High-quality studies establishing the efficacy of specific probiotic microbes at specific dosages are lacking. One prebiotic agent, lactulose, has shown some evidence of increasing stool water content and stool volume and accelerating stool transit and frequency in patients with constipation. The probiotic agent Lactobacillus casei rhamnosus may help soften stools and increases stool frequency in children with constipation. A variety of commercial products available in stores contain some probiotic and prebiotic components, but their efficacy has not been fully studied.



Surgical intervention as a means of treating severe constipation is necessary for only a limited number of patients with very severe constipation that has not responded to other treatments. The operation most commonly performed involves 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 leaking, obstructions of the small intestine, or other complications.


Alternative approaches

A variety of alternative, herbal, and other approaches are available. Solid scientific evidence is limited, but some people find flaxseed or sesame seed useful. Others have reported success using massage or acupressure.



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