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The lower digestive tract
Constipation is passage of small amounts of hard, dry bowel
fewer than three times a week. People who are constipated may find
it difficult and painful to have a bowel
movement. Other symptoms of constipation include feeling bloated,
uncomfortable, and sluggish.
Many people think they are constipated when, in fact, their bowel
movements are regular. For example, some people believe they are
constipated, or irregular, if they do not have a bowel movement
every day. However, there is no right number of daily or weekly
bowel movements. Normal may be three times a day or three times a
week depending on the person. Also, some people naturally have
firmer stools than others.
At one time or another, almost everyone gets constipated. Poor
diet and lack of exercise are usually the causes. In most cases,
constipation is temporary and not serious. Understanding its causes,
prevention, and treatment will help most people find relief.
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According to the 1996 National Health Interview Survey, about 3
million people in the United States have frequent constipation.
Those reporting constipation most often are women and adults age 65
and over. Pregnant women may have constipation, and it is a common
problem following childbirth or surgery.
Constipation is one of the most common gastrointestinal
complaints in the United States, resulting in about 2 million doctor
visits annually. However, most people treat themselves without
seeking medical help, as is evident from the millions of dollars
Americans spend on laxatives each year.
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To understand constipation, it helps to know how the colon (large
intestine) works. As food moves through the colon, it absorbs water
while forming waste products, or stool. Muscle contractions in the
colon push the stool toward the rectum. By the time stool reaches
the rectum, it is solid because most of the water has been
The hard and dry stools of constipation occur when the colon
absorbs too much water or if the colon's muscle contractions are
slow or sluggish, causing the stool to move through the colon too
slowly. Common causes of constipation are
- not enough fiber in the diet
- not enough liquids
- lack of exercise
- irritable bowel syndrome
- changes in life or routine such as pregnancy, older age, and
- abuse of laxatives
- ignoring the urge to have a bowel movement
- specific diseases such as stroke (by far the most common)
- problems with the colon and rectum
- problems with intestinal function (chronic idiopathic
The most common cause of constipation is a diet low in fiber
found in vegetables, fruits, and whole grains and high in fats found
in cheese, eggs, and meats. People who eat plenty of high-fiber
foods are less likely to become constipated.
Fiber--both soluble and insoluble--is the part of fruits,
vegetables, and grains that the body cannot digest. Soluble fiber
dissolves easily in water and takes on a soft, gel-like texture in
the intestines. Insoluble fiber passes through the intestines almost
unchanged. The bulk and soft texture of fiber help prevent hard, dry
stools that are difficult to pass.
According to the National Center for Health Statistics, Americans
eat an average of 5 to 14 grams of fiber daily,* short of the 20 to
35 grams recommended by the American Dietetic Association. Both
children and adults eat too many refined and processed foods from
which the natural fiber has been removed.
A low-fiber diet also plays a key role in constipation among
older adults, who may lose interest in eating and choose convenience
foods low in fiber. In addition, difficulties with chewing or
swallowing may force older people to eat soft foods that are
processed and low in fiber.
*National Center for Health Statistics. Dietary Intake
of Macronutrients, Micronutrients, and Other Dietary Constituents:
United States, 1988-94. Vital and Health Statistics, Series 11,
number 245. July 2002.
Liquids like water and juice add fluid to the colon and bulk to
stools, making bowel movements softer and easier to pass. People who
have problems with constipation should drink enough of these liquids
every day, about eight 8-ounce glasses. Liquids that contain
caffeine, like coffee and cola drinks, and alcohol have a
Lack of exercise can lead to constipation, although doctors do
not know precisely why. For example, constipation often occurs after
an accident or during an illness when one must stay in bed and
Some medications can cause constipation. They include
- pain medications (especially narcotics)
- antacids that contain aluminum and calcium
- blood pressure medications (calcium channel blockers)
- antiparkinson drugs
- iron supplements
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 people 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
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.
Several kinds of diseases can cause constipation:
- multiple sclerosis
- Parkinson's disease
- chronic idiopathic intestinal pseudo-obstruction
- spinal cord injuries
- underactive or overactive thyroid gland
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
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
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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Most people with constipation do not need extensive testing and
can be treated with changes in diet and exercise. For example, in
young people with mild symptoms, a medical history and physical
examination may be all the doctor needs to suggest successful
treatment. The tests the doctor performs depend on the duration and
severity of the constipation, the person's age, and whether blood in
stools, recent changes in bowel movements, or weight loss have
The doctor may ask a patient to describe his or her constipation,
including duration of symptoms, frequency of bowel movements,
consistency of stools, presence of blood in the stool, and toilet
habits (how often and where one has bowel movements). A record of
eating habits, medication, and level of physical activity or
exercise will also help the doctor determine the cause of
The clinical definition of constipation is any two of the
following symptoms for at least 12 weeks (not necessarily
consecutive) in the previous 12 months:
- straining during bowel movements
- lumpy or hard stool
- sensation of incomplete evacuation
- sensation of anorectal blockage/obstruction
- fewer than three bowel movements per week
A physical exam may include a rectal exam with a gloved,
lubricated finger to evaluate the tone of the muscle that closes off
the anus (anal sphincter) and to detect tenderness, obstruction, or
blood. In some cases, blood and thyroid tests may be necessary to
look for thyroid disease and serum calcium or to rule out
inflammatory, neoplastic, metabolic, and other systemic
Extensive testing usually is reserved for people with severe
symptoms, for those with sudden changes in number and consistency of
bowel movements or blood in the stool, and for older adults.
Additional tests that may be used to evaluate constipation
- colorectal transit study
- anorectal function tests
Because of an increased risk of colorectal cancer in older
adults, the doctor may use tests to rule out a diagnosis of cancer,
- barium enema x ray
- sigmoidoscopy or colonoscopy
This test, reserved for those
with chronic constipation, shows how well food moves through the
colon. The patient swallows capsules containing small markers that
are visible on an x ray. The movement of the markers through the
colon is monitored with abdominal x rays taken several times 3 to 7
days after the capsule is swallowed. The patient follows a
high-fiber diet during the course of this test.
These tests diagnose
constipation caused by abnormal functioning of the anus or rectum
(anorectal function). Anorectal manometry evaluates anal sphincter
muscle function. For this test, a catheter or air-filled balloon
inserted into the anus is slowly pulled back through the sphincter
muscle to measure muscle tone and contractions.
Defecography is an x ray of the anorectal area that evaluates
completeness of stool elimination, identifies anorectal
abnormalities, and evaluates rectal muscle contractions and
relaxation. During the exam, the doctor fills the rectum with a soft
paste that is the same consistency as stool. The patient sits on a
toilet positioned inside an x ray machine and then relaxes and
squeezes the anus to expel the paste. The doctor studies the x rays
for anorectal problems that occurred as the paste was expelled.
This exam involves viewing the rectum,
colon, and lower part of the small intestine to locate any problems.
This part of the digestive tract is known as the bowel. This test
may show intestinal obstruction and Hirschsprung's disease, a lack
of nerves within the colon.
The night before the test, bowel cleansing, also called bowel
prep, is necessary to clear the lower digestive tract. The patient
drinks a special liquid to flush out the bowel. A clean bowel is
important, because even a small amount of stool in the colon can
hide details and result in an incomplete exam.
Because the colon does not show up well on x rays, the doctor
fills it with barium, a chalky liquid that makes the area visible.
Once the mixture coats the inside of colon and rectum, x rays are
taken that reveal their shape and condition. The patient may feel
some abdominal cramping when the barium fills the colon, but usually
feels little discomfort after the procedure. Stools may be a whitish
color for a few days after the exam.
An examination of the rectum
and lower (sigmoid) colon is called a sigmoidoscopy. An examination
of the rectum and entire colon is called a colonoscopy.
The patient usually has a liquid dinner the night before a
sigmoidoscopy and takes an enema early the next morning. A light
breakfast and a cleansing enema an hour before the test may also be
To perform a sigmoidoscopy, the doctor uses a long, flexible tube
with a light on the end called a sigmoidoscope to view the rectum
and lower colon. First, the doctor examines the rectum with a
gloved, lubricated finger. Then, the sigmoidoscope is inserted
through the anus into the rectum and lower colon. The procedure may
cause a mild sensation of wanting to move the bowels and abdominal
pressure. Sometimes the doctor fills the colon with air to get a
better view. The air may cause mild cramping.
To perform a colonoscopy, the doctor uses a flexible tube with a
light on the end called a colonoscope to view the entire colon. This
tube is longer than a sigmoidoscope. The same bowel cleansing used
for the barium x ray is needed to clear the bowel of waste. The
patient is lightly sedated before the exam. During the exam, the
patient lies on his or her side and the doctor inserts the tube
through the anus and rectum into the colon. If an abnormality is
seen, the doctor can use the colonoscope to remove a small piece of
tissue for examination (biopsy). The patient may feel gassy and
bloated after the procedure.
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Although treatment depends on the cause, severity, and duration,
in most cases dietary and lifestyle changes will help relieve
symptoms of constipation and help prevent it.
A diet with enough fiber (20 to 35 grams each day) helps form
soft, bulky stool. A doctor or dietitian can help plan an
appropriate diet. High-fiber foods include beans, whole grains and
bran cereals, fresh fruits, and vegetables such as asparagus,
brussels sprouts, cabbage, and carrots. For people prone to
constipation, limiting foods that have little or no fiber, such as
ice cream, cheese, meat, and processed foods, is also important.
Other changes that can help treat and prevent constipation
include drinking enough water and other liquids such as fruit and
vegetable juices and clear soups, engaging in daily exercise, and
reserving enough time to have a bowel movement. In addition, the
urge to have a bowel movement should not be ignored.
Most people who are mildly constipated do not need laxatives.
However, for those who have made diet and lifestyle changes and are
still constipated, doctors may recommend laxatives or enemas for a
limited time. These treatments can help retrain a chronically
sluggish bowel. For children, short-term treatment with laxatives,
along with retraining to establish regular bowel habits, also helps
A doctor should determine when a patient needs a laxative and
which form is best. Laxatives taken by mouth are available in
liquid, tablet, gum, powder, and granule forms. They work in various
- Bulk-forming laxatives generally are considered the safest but
can interfere with absorption of some medicines. These laxatives, also known
as fiber supplements, are taken with water. They absorb water in the intestine
and make the stool softer. Brand names include Metamucil, Citrucel, Konsyl,
- Stimulants cause rhythmic muscle contractions in the intestines.
Brand names include Correctol, Dulcolax, Purge, and Senokot. Studies suggest
that phenolphthalein, an ingredient in some stimulant laxatives, might increase
a person's risk for cancer. The Food and Drug Administration has proposed
a ban on all over-the-counter products containing phenolphthalein. Most
laxative makers have replaced or plan to replace phenolphthalein with a
- Stool softeners provide moisture to the stool and prevent dehydration.
These laxatives are often recommended after childbirth or surgery. Products
include Colace and Surfak.
- Lubricants grease the stool enabling it to move through the intestine
more easily. Mineral oil is the most common example.
- Saline laxatives act like a sponge to draw water into the colon
for easier passage of stool. Laxatives in this group include Milk of Magnesia
and Haley's M-O.
People who are dependent on laxatives need to slowly stop using
them. A doctor can assist in this process. In most people, this
restores the colon's natural ability to contract.
Treatment may be directed at a specific cause. For example, the
doctor may recommend discontinuing medication or performing surgery
to correct an anorectal problem such as rectal prolapse.
People with chronic constipation caused by anorectal dysfunction
can use biofeedback to retrain the muscles that control release of
bowel movements. Biofeedback involves using a sensor to monitor
muscle activity that at the same time can be displayed on a computer
screen, allowing for an accurate assessment of body functions. A
health care professional uses this information to help the patient
learn how to use these muscles.
Surgical removal of the colon may be an option for people with
severe symptoms caused by colonic inertia. However, the benefits of
this surgery must be weighed against possible complications, which
include abdominal pain and diarrhea.
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Sometimes constipation can lead to complications. These
complications include hemorrhoids caused by straining to have a
bowel movement or anal fissures (tears in the skin around the anus)
caused when hard stool stretches the sphincter muscle. As a result,
rectal bleeding may occur, appearing as bright red streaks on the
surface of the stool. Treatment for hemorrhoids may include warm tub
baths, ice packs, and application of a special cream to the affected
area. Treatment for anal fissure may include stretching the
sphincter muscle or surgical removal of tissue or skin in the
Sometimes straining causes a small amount of intestinal lining to
push out from the anal opening. This condition, known as rectal
prolapse, may lead to secretion of mucus from the anus. Usually
eliminating the cause of the prolapse, such as straining or
coughing, is the only treatment necessary. Severe or chronic
prolapse requires surgery to strengthen and tighten the anal
sphincter muscle or to repair the prolapsed lining.
Constipation may also cause hard stool to pack the intestine and
rectum so tightly that the normal pushing action of the colon is not
enough to expel the stool. This condition, called fecal impaction,
occurs most often in children and older adults. An impaction can be
softened with mineral oil taken by mouth and by an enema. After
softening the impaction, the doctor may break up and remove part of
the hardened stool by inserting one or two fingers into the
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NIDDK's Division of Digestive Diseases and Nutrition supports
basic and clinical research into gastrointestinal conditions,
including constipation. Among other areas, researchers are studying
the anatomical and physiological characteristics of rectoanal
motility and the use of new medications and behavioral techniques,
such as biofeedback, to treat constipation.
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- Constipation affects almost everyone at one time or another.
- Many people think they are constipated when, in fact, their bowel movements
- The most common causes of constipation are poor diet and lack of exercise.
- Additional causes of constipation include medications, irritable bowel
syndrome, abuse of laxatives, and specific diseases.
- A medical history and physical examination may be the only diagnostic
tests needed before the doctor suggests treatment.
- In most cases, following these simple tips will help relieve symptoms
and prevent recurrence of constipation:
- Eat a well-balanced, high-fiber diet that includes beans, bran, whole
grains, fresh fruits, and vegetables.
- Drink plenty of liquids.
- Exercise regularly.
- Set aside time after breakfast or dinner for undisturbed visits to
- Do not ignore the urge to have a bowel movement.
- Understand that normal bowel habits vary.
- Whenever a significant or prolonged change in bowel habits occurs,
check with a doctor.
- Most people with mild constipation do not need laxatives. However, doctors
may recommend laxatives for a limited time for people with chronic constipation.
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for Functional Gastrointestinal Disorders Inc.
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