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Constipation ˌkän(t)-stə-ˈpā-shən

by Norton J. Greenberger, MD

Constipation is difficult or infrequent bowel movements, hard stool, or a feeling that the rectum is not totally empty after a bowel movement (incomplete evacuation). For constipation in children, see Constipation in Children.

Constipation may be acute or chronic. Acute constipation begins suddenly and noticeably. Chronic constipation may begin gradually and persists for months or years.

Many people believe they are constipated if they do not have a bowel movement every day. However, daily bowel movements are not normal for everyone. It is normal to have anywhere from 1 to 3 bowel movements per day to 2 to 3 bowel movements per week. Having infrequent bowel movements does not necessarily indicate a problem unless there has been a substantial change from previous patterns. The same is true of the color, size, and consistency of stool. People often blame constipation for many symptoms (such as abdominal discomfort, nausea, fatigue, and poor appetite) that are actually the result of other disorders (such as irritable bowel syndrome [IBS] and depression). People should not expect all symptoms to be relieved by a daily bowel movement, and measures to aid bowel habits, such as laxatives and enemas, should not be overused. However, people may harmlessly help relieve their symptoms by eating more fruits, vegetables, fiber, and cereals. Foods that can affect the frequency of bowel movements are listed in see Table: Foods That Often Affect Gastrointestinal Function.

Foods That Often Affect Gastrointestinal Function

Foods Likely to Cause Loose Bowel Movements and/or Excessive Gas

All caffeine-containing beverages especially coffee with chicory

Fruit juices: Orange, cranberry, apple

Asparagus and cruciferous vegetables such as broccoli, cauliflower, cabbage, and Brussels sprouts

Bran cereal, whole wheat bread, and high-fiber foods

Pastry, candy, chocolate, waffle syrup, and doughnuts

Wine (more than 3 glasses in susceptible people)

Milk and milk products (in lactose-sensitive people)

Foods Likely to Cause Constipation or Help Control Loose Bowel Movements

Rice, bread, potatoes, and pasta

Meat, veal, poultry, and fish

Cooked vegetables

Bananas

Complications

The complications of constipation include

  • Hemorrhoids

  • Rectal prolapse

  • Anal fissure

  • Diverticular disease

  • Fecal impaction

Excessive straining during bowel movements increases pressure on the veins around the anus and can lead to hemorrhoids and, rarely, protrusion of the rectum through the anus (rectal prolapse). Passing hard stool can cause a split in the skin of the anus (anal fissure). Each of these complications can make having a bowel movement uncomfortable and make people reluctant to move their bowels. Putting off bowel movements can cause a vicious circle of worsening constipation and complications.

Diverticular disease can develop if the walls of the large intestine are damaged by the increased pressure required to move small, hard stools. Damage to the walls of the large intestine leads to the formation of balloon-like sacs or outpocketings (diverticula), which can become clogged and inflamed (diverticulitis). Diverticula sometimes bleed and rarely rupture (causing peritonitis).

Fecal impaction, in which stool in the rectum and last part of the large intestine hardens and completely blocks the passage of other stool, sometimes develops in people with constipation. Fecal impaction leads to cramps, rectal pain, and strong but futile efforts to defecate. Sometimes, watery mucus or liquid stool oozes around the blockage, which gives the false impression of diarrhea (paradoxic diarrhea). Fecal impaction is especially common among older people, particularly those who are bedridden or have decreased physical activity, pregnant women, and people who have been given barium by mouth or as an enema for certain types of x-ray tests.

Overconcern with regular bowel movements causes many people to abuse their bowels with laxatives, suppositories, and enemas. Overusing these treatments can actually inhibit the bowel’s normal contractions and worsen constipation. People with obsessive-compulsive disorder (OCD) often feel the need to rid their body daily of “unclean” wastes or "toxins." Such people often spend excessive time on the toilet or become chronic users of laxatives.

Causes

The most common causes of constipation include

  • Changes in diet (such as decreased fluid intake, low-fiber diet, and/or constipating foods)

  • Drugs that slow the bowels

  • Disordered defecation

  • Laxative overuse

Dietary causes are very common. Dehydration causes constipation because the body tries to conserve water in the blood by removing additional water from the stool. Stool that contains less water is harder to pass. Fruits, vegetables, cereals, and other fiber-containing foods are the natural laxatives of the digestive tract. People who do not eat enough of these foods can become constipated. Lack of fiber (the indigestible part of food) in the diet can lead to constipation because fiber helps hold water in the stool and increases its bulk, making it easier to pass.

The most common drugs that can slow the bowels include opioids, iron salts, and drugs with anticholinergic effects (such as many antihistamines and tricyclic antidepressants—see Anticholinergic: What Does It Mean?). Other drugs include aluminum hydroxide (common in over-the-counter antacids), bismuth subsalicylate, certain drugs that lower blood pressure (antihypertensives), and many sedatives.

Disordered defecation (dyschezia) refers to a problem with the bowels generating enough force to propel stool from the rectum and/or difficulty relaxing the muscle fibers around the rectum and the external anal sphincter during defecation. People with dyschezia sense the need to have a bowel movement but cannot. Even stool that is not hard may be difficult to pass. People with irritable bowel syndrome (IBS—see Irritable Bowel Syndrome (IBS)) may have IBS-disordered defecation.

People who frequently use laxatives and/or enemas often lose the ability to move their bowels without such aids. A vicious circle can result with constipation leading to more laxative use and thus more constipation.

Less common causes of constipation include specific medical disorders ( Some Causes and Features of Constipation), such as intestinal obstruction, and certain metabolic disorders and neurologic disorders. Constipation also can occur during any major illness that requires prolonged bed rest (because physical activity helps the intestines move stool along), with decreased food intake, with use of drugs that can cause constipation, and after a head or spinal cord injury. In many cases, however, the cause of constipation is unknown.

Constipation is sometimes caused by obstruction of the large intestine. Obstruction can be caused by a large cancer, especially in the last portion of the large intestine, that blocks the movement of stool. People who previously had abdominal surgery may develop obstruction, usually of the small intestine, because bands of fibrous tissues (adhesions) can form around the intestines and impede the flow of stool.

Disorders and diseases that often cause constipation include an underactive thyroid gland (hypothyroidism), high blood calcium levels (hypercalcemia), and Parkinson disease. People with diabetes often develop nerve damage (neuropathy). If the neuropathy affects nerves to the digestive tract, the intestines may slow down, resulting in constipation. Spinal cord injury can also interfere with the nerves to the intestines and cause constipation.

Evaluation

Not every episode of constipation requires immediate evaluation by a doctor. The following information can help people decide whether a doctor’s evaluation is needed and help them know what to expect during the evaluation.

Warning signs

In people with constipation, certain symptoms and characteristics are cause for concern. They include

  • Distended, swollen abdomen

  • Vomiting

  • Blood in stool

  • Weight loss

  • New/worsening severe constipation in older people

When to see a doctor

People who have warning signs should see a doctor right away, unless the only warning signs are weight loss and/or new constipation in older people. In such cases, a delay of a few days to a week is not harmful.

People who have constipation but no warning signs should call their doctor, who can help decide how quickly they need to be seen. Depending on the person's other symptoms and known disorders, doctors may wish to see the person within a few days or may simply recommend trying changes in diet and/or a mild laxative.

What the doctor does

Doctors first ask questions about the person's symptoms and medical history. Doctors then do a physical examination. What they find during the history and physical examination often suggests a cause of the constipation and the tests that may need to be done (see Table: Some Causes and Features of Constipation).

During the history, doctors ask about the following:

  • Stool frequency, consistency, and the need to strain or use maneuvers (such as pushing on the area between the scrotum or vagina and the anus [perineum]) during defecation)

  • Feeling of incomplete evacuation

  • Satisfaction after defecation, including how often and how long people have used laxatives or enemas

  • Diet and physical activity level, particularly any change in these factors

  • Prescription and nonprescription drug use (particularly those known to cause constipation)

Doctors also ask about symptoms of metabolic (such as hypothyroidism and diabetes) and neurologic (such as spinal cord injury) disorders.

During the physical examination, doctors look at the following:

  • Signs of bodywide (systemic) disease, including weight loss, fever, and severe wasting away of muscle and fat tissue (cachexia)

  • The abdomen for distention and masses

  • The rectum for fissures, hemorrhoids, blood, or masses (including fecal impaction) and also anal muscle tone and sensation

Some Causes and Features of Constipation

Cause

Examples/Common Features*

Tests

Acute constipation

Acute intestinal obstruction

Twisting of a loop of intestine (volvulus), hernia, adhesions, and fecal impaction

Usually vomiting, crampy abdominal pain, and a distended abdomen

Abdominal x-rays

Sometimes CT

Ileus (temporary absence of the contractile movements of the intestine)

Major acute illness, such as sepsis (a severe infection of the bloodstream)

Immediately after abdominal surgery

Recent head or spinal cord injury

Prolonged bed rest

Abdominal x-rays

Drugs

Drugs with anticholinergic effects, such as antihistamines, some antidepressants, antipsychotic drugs, drugs used to treat Parkinson disease, and drugs that reduce or stop muscle spasms in the digestive tract (antispasmodic drugs)

Drugs containing certain metals (iron, aluminum, calcium, barium, or bismuth)

Opioids

Calcium channel blockers

Usually constipation that begins shortly after starting a new drug

A doctor's examination to exclude other causes of constipation

Sometimes stopping the drug to see whether constipation resolves

Chronic constipation

Colon cancer

Often constipation that has recently developed, persists for weeks, and gradually worsens as the tumor grows

Sometimes blood in stool (blood may be visible or detected during a doctor's examination)

Colonoscopy with biopsy

Metabolic disorders

Diabetes mellitus, an underactive thyroid gland (hypothyroidism), high levels of calcium in the blood (hypercalcemia), kidney failure, or pregnancy

Blood tests

Central nervous system disorders (affecting the brain or spinal cord)

Parkinson disease, multiple sclerosis, stroke, or spinal cord injury or disorders

MRI and/or CT

Peripheral nervous system disorders (affecting nerves outside the brain and spinal cord)

Hirschsprung disease, neurofibromatosis, or autonomic neuropathy

A doctor’s examination

Sometimes x-rays after barium is inserted in the rectum (barium enema) and/or biopsy

Systemic disorders

Systemic sclerosis, amyloidosis, skin inflammation plus muscle inflammation and muscle degeneration (dermatomyositis), or weakness and stiff muscles (myotonic dystrophy)

A doctor’s examination

Sometimes biopsy and/or blood tests

Functional disorders

Inactive colon (colonic inertia), irritable bowel syndrome, or disordered defecation

Often a sense of a blockage in the anus and/or rectum, prolonged or difficult defecation, or excessive straining

A doctor’s examination

Sometimes sigmoidoscopy

Dietary factors

Low-fiber diet or chronic laxative abuse

A doctor’s examination

*Features include symptoms and the results of the doctor's examination. Features mentioned are typical but not always present.

There is some overlap between causes of acute and chronic constipation. In particular, drugs are common causes of both.

CT = computed tomography; MRI = magnetic resonance imaging.

Testing

The need for tests depends on what doctors find during the history and physical examination, particularly whether warning signs are present. When the cause of the constipation is clear (such as due to drugs, injury, or bed rest), doctors often treat the person’s symptoms and do no testing.

People with symptoms of intestinal obstruction undergo abdominal x-rays and possibly a computed tomography (CT) scan. Most people with no clear cause or whose symptoms have not been relieved with treatment should have tests. Typically, doctors do a colonoscopy (to detect cancer) and blood tests to check for an underactive thyroid gland (hypothyroidism) or high calcium levels in the blood (hypercalcemia).

People whose initial test results are normal but whose symptoms are not relieved with treatment usually require further testing. If the main symptom is infrequent defecation, doctors do certain tests, such as having people swallow small, slightly radioactive objects that can be tracked using a scanner (a type of radionuclide scanning—see Radionuclide Scanning), to measure how long it takes stool to leave the intestines. If the main symptom is difficulty with defecation, doctors measure the pressure inside the anus and rectum.

Treatment

Any underlying disorder causing constipation must be treated. When possible, drugs that cause constipation are stopped or changed.

Constipation is best prevented with a combination of exercise, a high-fiber diet, and an adequate intake of fluids. When a potentially constipating drug is prescribed and/or people are placed on bed rest, doctors often give a laxative and recommend increased intake of dietary fiber and fluids rather than waiting for constipation to develop.

There are three approaches to treating people with constipation:

  • Diet and behavior

  • Laxatives

  • Enemas

Doctors are cautious with use of laxatives, suppositories, and enemas because they can cause diarrhea, dehydration, cramps, and/or dependence on laxatives. People with sudden abdominal pain of unknown cause, inflammatory bowel disorders, intestinal obstruction, gastrointestinal bleeding, or fecal impaction should not use laxatives or enemas.

Diet and behavior

People need to ingest enough fiber in their diet (typically 15 to 20 grams per day) to ensure adequate stool bulk. Vegetables, fruits, and bran are excellent sources of fiber. Many people find it convenient to sprinkle 2 or 3 teaspoons of unrefined miller’s bran on high-fiber cereal or fruit 2 or 3 times a day. To work well, fiber must be consumed with plenty of fluids.

People should try to make changes to their behavior. For example, people should try to move their bowels at the same time every day, preferably 15 to 45 minutes after breakfast, because eating food stimulates movement in the colon. Glycerin suppositories may also help people have regular, unhurried bowel movements.

Doctors explain to people why diet and behavior modification are important in treating constipation. Doctors also explain that daily bowel movements are not necessary, that the bowel must be given a chance to function, and that frequent use of laxatives or enemas (more than once every 3 days) denies the bowel that chance.

Laxatives

Some laxatives are safe for long-term use. Other laxatives should be used only occasionally. Some laxatives are good for preventing constipation, others for treating it. There are several classes of laxatives, including the following:

  • Bulking agents

  • Stool softeners

  • Osmotic agents

  • Stimulants

Bulking agents, such as bran and psyllium (also available in the fiber of many vegetables), add bulk to the stool and absorb water. The increased bulk stimulates the natural contractions of the intestine, and bulkier stools that contain more water are softer and easier to pass. Bulking agents act slowly and gently and are among the safest ways to promote regular bowel movements. These agents generally are taken in small amounts at first. The dose is increased gradually until regularity is achieved. People who use bulking agents should always drink plenty of fluids. These agents may cause problems with increased gas (flatulence) and bloating.

Stool softeners, such as docusate or mineral oil, act slowly to soften stools, making them easier to pass. In addition, the slightly increased bulk that results from these drugs stimulates the natural contractions of the large intestine and thus promotes easier elimination. Some people, however, find the softened nature of the stool unpleasant. Stool softeners are best reserved for people who must avoid straining, such as people who have hemorrhoids or have recently had abdominal surgery.

Osmotic agents pull large amounts of water into the large intestine, making the stool soft and loose. The excess fluid also stretches the walls of the large intestine, stimulating contractions. These laxatives consist of salts or sugars that are poorly absorbed. They may cause fluid retention in people who have kidney disease or heart failure, especially when given in large or frequent doses. In general, osmotic laxatives are reasonably safe even when used regularly. However, osmotic agents that contain magnesium and phosphate are partially absorbed into the bloodstream and can be harmful to older people, people who have kidney failure or kidney disease, and people who take drugs that affect kidney function (such as diuretics, angiotensin-converting enzyme [ACE] inhibitors, and angiotensin II receptor blockers). Although a rare occurrence, some people have developed kidney failure from taking sodium phosphate laxatives by mouth to clear stool from the intestine before x-rays of the digestive tract are taken or before a colonoscopy is done.

Stimulant laxatives (such as phenolphthalein, bisacodyl, and anthraquinones) contain irritating substances, such as senna and cascara. These substances stimulate the walls of the large intestine, causing them to contract and move the stool. They are useful for preventing constipation in people who are taking drugs that will almost certainly cause constipation, such as opioids. Stimulant laxatives are also often used to empty the large intestine before diagnostic tests are done.

Taken by mouth, stimulant laxatives usually cause a semisolid bowel movement in 6 to 8 hours, but they often cause cramping as well. As suppositories, stimulant laxatives often work in 15 to 60 minutes. Prolonged use of stimulant laxatives can create abnormal deposits of a dark pigment in the lining of the large intestine (a condition called melanosis coli). Other side effects include allergic reactions and loss of electrolytes from the blood. Also, the large intestine can become dependent on stimulant laxatives, leading to lazy bowel syndrome. Therefore, stimulant laxatives should be used only for brief periods.

Bisacodyl is an effective drug for chronic constipation. Anthraquinones are found in senna, cascara sagrada, aloe, and rhubarb and are common components of herbal and over-the-counter laxatives. Lubiprostone works by making the large intestine secrete extra fluid, which makes stool easier to pass. Unlike other stimulant laxatives, lubiprostone is safe for prolonged use.

Agents Used to Prevent or Treat Constipation

Agent

Some Side Effects

Comments

Bulking agents (fiber)*

Bran

Bloating, passing of gas (flatulence), and poor absorption of iron and calcium

Bulking agents generally are used to prevent or control chronic constipation.

Polycarbophil

Bloating and flatulence

Methylcellulose

Less bloating than with other fiber agents

Psyllium

Bloating and flatulence

Stool softeners

Docusate

Stool softeners may be used to treat constipation and are often used to help prevent it.

Docusate is not effective for severe constipation.

Glycerin

Rectal irritation

Mineral oil

Lung inflammation caused by fats in the lungs (lipid pneumonia), poor absorption of fat-soluble vitamins, dehydration, and loss of control over bowel movements (fecal incontinence)

Osmotic agents

Lactulose

Abdominal cramps and flatulence

Osmotic agents are better for treating constipation than for preventing it.

Magnesium salts (magnesium hydroxide and magnesium citrate)

Too much magnesium in the body (magnesium toxicity), dehydration, abdominal cramps, and fecal incontinence

Polyethylene glycol

Fecal incontinence (related to dosage)

Sodium phosphate

Rare cases of sudden kidney failure

Sorbitol

Abdominal cramps and flatulence

Stimulant laxatives

Anthraquinones (found in senna, cascara, and castor oil)

Abdominal cramps and dehydration

Stimulant laxatives are not used if there is a possibility of an intestinal obstruction.

Prolonged use can damage the large intestine.

Lubiprostone can be used for chronic constipation. It is available for long-term use.

Bisacodyl

Fecal incontinence, a low level of potassium in the blood (hypokalemia), abdominal cramps, and rectal burning with daily use of the suppository form

Linaclotide

Abdominal cramps, flatulence

Not used in children

Lubiprostone

Nausea, particularly when the drug is taken on an empty stomach

Enemas

Mineral oil or olive oil retention

Fecal incontinence

Although rare, giving an enema can injure the rectum if the procedure is done roughly.

Tap water

Fluid overload if a lot of water is absorbed

Phosphate

A high level of phosphate in the blood (hyperphosphatemia)

Soapsuds

Cramps

*The dose of fiber supplements should be gradually increased over several weeks to the recommended dose.

Lubiprostone and linaclotide are available only by prescription.

Enemas

Enemas mechanically flush stool from the rectum and lower part of the large intestine. Small-volume enemas can be purchased in squeeze bottles at a pharmacy. They can also be given with a reusable squeeze-ball device. However, small-volume enemas are often inadequate, especially for older people, whose rectal capacity increases with age, thus making the rectum more easily stretched. Larger-volume enemas are given with an enema bag.

Plain water is often the best fluid to be used as an enema. The water should be room temperature to slightly warm, not hot or cold. About 5 to 10 fluid ounces (150 to 300 milliliters) is gently directed into the rectum. (C aution : Additional force is dangerous. ) People then expel the water, washing stool out with it.

Various ingredients are sometimes added to enemas. Prepackaged enemas often contain small amounts of salts, often phosphates. Other enemas contain small amounts of soap (soapsuds enema), which has a stimulant laxative effect, or mineral oil. These enemas offer little advantage, however, to plain water.

Very large-volume enemas, calledcolonic enemas, are rarely used in medical practice. Doctors use colonic enemas in people with very severe constipation (obstipation). Some practitioners of alternative medicine use colonic enemas in the belief that cleansing the large intestine is beneficial. Tea, coffee, and other substances are often added to colonic enemas but have no proven health value and may be dangerous.

Fecal impaction

Fecal impaction cannot be treated by modifying the diet or taking laxatives. Fecal impaction is first treated with enemas of tap water followed by small enemas of commercially prepared solutions. If these enemas do not work, the hard stool must be removed by a doctor or nurse using a gloved finger. This procedure is painful, so an anesthetic (such as lidocaine 5% ointment) is often applied. Some people need to be sedated. Typically, an enema is given after the hard stool is removed.

Essentials for Older People

The rectum enlarges as people age, and increased storage of stool in the rectum means that older people often need to have larger volumes of stool in their rectum in order to feel the urge to defecate. The increased rectal volume also allows hard stool to become impacted.

Other common factors in older people that lead to constipation include increased use of constipating drugs, a low-fiber diet, coexisting medical conditions (such as diabetes), and reduced physical activity. Many older people also have misconceptions about normal bowel habits and use laxatives too often.

Key Points

  • Drug causes (such as chronic laxative abuse or use of anticholinergic or opioid drugs) are common.

  • Doctors look for intestinal obstruction when constipation is sudden and severe.

  • Symptoms may be treated if no warning signs are found and doctors find no evidence of disordered defecation.

Resources In This Article

Drugs Mentioned In This Article

  • Generic Name
    Select Brand Names
  • CHOLAC
  • AMITIZA
  • DULCOLAX
  • LINZESS
  • XYLOCAINE