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Friday, May 09, 2008
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Irritable
Bowel Syndrome
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Irritable
bowel syndrome (IBS) is a common disorder of the intestines
that leads to crampy pain, gassiness, bloating, and changes
in bowel habits. Some people with IBS have constipation
(difficult or infrequent bowel movements); others have diarrhea
(frequent loose stools, often with an urgent need to move
the bowels); and some people experience both. Sometimes
the person with IBS has a crampy urge to move the bowels
but cannot do so.
Through the
years, IBS has been called by many names--colitis, mucous
colitis, spastic colon, spastic bowel, and functional
bowel disease. Most of these terms are inaccurate. Colitis,
for instance, means inflammation of the large intestine
(colon). IBS, however, does not cause inflammation and
should not be confused with another disorder, ulcerative
colitis.
The cause of
IBS is not known, and as yet there is no cure. Doctors
call it a functional disorder because there is no sign
of disease when the colon is examined. IBS causes a great
deal of discomfort and distress, but it does not cause
permanent harm to the intestines and does not lead to
intestinal bleeding of the bowel or to a serious disease
such as cancer. Often IBS is just a mild annoyance, but
for some people it can be disabling. They may be unable
to go to social events, to go out to a job, or to travel
even short distances. Most people with IBS, however, are
able to control their symptoms through medications prescribed
by their physicians, diet, and stress management.
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The
colon, which is about 6 feet long, connects the small intestine
with the rectum and anus. The major function of the colon
is to absorb water and salts from digestive products that
enter from the small intestine. Two quarts of liquid matter
enter the colon from the small intestine each day. This
material may remain there for several days until most of
the fluid and salts are absorbed into the body. The stool
then passes through the colon by a pattern of movements
to the left side of the colon, where it is stored until
a bowel movement occurs.
Colon motility
(contraction of intestinal muscles and movement of its
contents) is controlled by nerves and hormones and by
electrical activity in the colon muscle. The electrical
activity serves as a "pacemaker" similar to the mechanism
that controls heart function.
Movements of
the colon propel the contents slowly back and forth but
mainly toward the rectum. A few times each day strong
muscle contractions move down the colon pushing fecal
material ahead of them. Some of these strong contractions
result in a bowel movement.
Because doctors
have been unable to find an organic cause, IBS often has
been thought to be caused by emotional conflict or stress.
While stress may worsen IBS symptoms, research suggests
that other factors also are important. Researchers have
found that the colon muscle of a person with IBS begins
to spasm after only mild stimulation. The person with
IBS seems to have a colon that is more sensitive and reactive
than usual, so it responds strongly to stimuli that would
not bother most people.
Ordinary events
such as eating and distention from gas or other material
in the colon can cause the colon to overreact in the person
with IBS. Certain medicines and foods may trigger spasms
in some people. Sometimes the spasm delays the passage
of stool, leading to constipation. Chocolate, milk products,
or large amounts of alcohol are frequent offenders. Caffeine
causes loose stools in many people, but it is more likely
to affect those with IBS. Researchers also have found
that women with IBS may have more symptoms during their
menstrual periods, suggesting that reproductive hormones
can increase IBS symptoms.
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If
you are concerned about IBS, it is important to realize
that normal bowel function varies from person to person.
Normal bowel movements range from as many as three stools
a day to as few as three a week. A normal movement is one
that is formed but not hard, contains no blood, and is passed
without cramps or pain.
People with
IBS, on the other hand, usually have crampy abdominal
pain with painful constipation or diarrhea. In some people,
constipation and diarrhea alternate. Sometimes people
with IBS pass mucus with their bowel movements. Bleeding,
fever, weight loss, and persistent severe pain are not
symptoms of IBS but may indicate other problems.
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IBS
usually is diagnosed after doctors exclude the presence
of disease. To get to that point, the doctor will take a
complete medical history that includes a careful description
of symptoms. A physical examination and laboratory tests
will be done. A stool sample will be tested for evidence
of bleeding. The doctor also may do diagnostic procedures
such as x-rays or endoscopy (viewing the colon through a
flexible tube inserted through the anus) to find out if
there is disease.
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The
potential for abnormal function of the colon is always present
in people with IBS, but a trigger also must be present to
cause symptoms. The most likely culprits seem to be diet
and emotional stress. Many people report that their symptoms
occur following a meal or when they are under stress. No
one is sure why this happens, but scientists have some clues.
Eating causes
contractions of the colon. Normally, this response may
cause an urge to have a bowel movement within 30 to 60
minutes after a meal. In people with IBS, the urge may
come sooner with cramps and diarrhea.
The strength
of the response is often related to the number of calories
in a meal and especially the amount of fat in a meal.
Fat in any form (animal or vegetable) is a strong stimulus
of colonic contractions after a meal. Many foods contain
fat, especially meats of all kinds, poultry skin, whole
milk, cream, cheese, butter, vegetable oil, margarine,
shortening, avocados, and whipped toppings.
Stress also
stimulates colonic spasm in people with IBS. This process
is not completely understood, but scientists point out
that the colon is controlled partly by the nervous system.
Stress reduction (relaxation) training or counseling and
support help relieve IBS symptoms in some people. However,
doctors are quick to note that this does not mean IBS
is the result of a personality disorder. IBS is at least
partly a disorder of colon motility.
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For
many people, eating a proper diet lessens IBS symptoms.
Before changing your diet, it is a good idea to keep a journal
noting which foods seem to cause distress. Discuss your
findings with your doctor. You also may want to consult
a registered dietitian, who can help you make changes in
your diet. For instance, if dairy products cause your symptoms
to flare up, you can try eating less of those foods. Yogurt
might be tolerated better because it contains organisms
that supply lactase, the enzyme needed to digest lactose,
the sugar found in milk products. Because dairy products
are an important source of calcium and other nutrients that
your body needs, be sure to get adequate nutrients in the
foods that you substitute.
Dietary fiber
may lessen IBS symptoms in many cases. Whole grain breads
and cereals, beans, fruits, and vegetables are good sources
of fiber. Consult your doctor before using an over-the-counter
fiber supplement. High-fiber diets keep the colon mildly
distended, which may help to prevent spasms from developing.
Some forms of fiber also keep water in the stools, thereby
preventing hard stools that are difficult to pass. Doctors
usually recommend that you eat just enough fiber so that
you have soft, easily passed, and painless bowel movements.
High-fiber diets may cause gas and bloating, but within
a few weeks, these symptoms often go away as your body
adjusts to the diet.
Large meals
can cause cramping and diarrhea in people with IBS. Symptoms
may be eased if you eat smaller meals more often or just
eat smaller portions. This should help, especially if
your meals are low in fat and high in carbohydrates such
as pasta, rice, whole-grain breads and cereals, fruits,
and vegetables.
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There
is no standard way of treating IBS. Your doctor may prescribe
fiber supplements or occasional laxatives if you are constipated.
Some doctors prescribe drugs that control colon muscle spasms,
drugs that slow the movement of food through the digestive
system, or tranquilizers, all of which may relieve symptoms.
Antidepressant drugs also are used sometimes in patients
who are depressed.
It is important
to follow the physician's instructions when taking IBS
medications--particularly laxatives, which can be habit
forming if not used carefully.
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IBS
has not been shown to lead to any serious, organic diseases.
No link has been established between IBS and inflammatory
bowel diseases such as Crohn's disease or ulcerative colitis.
IBS does not lead to cancer. Some patients have a more severe
form of IBS, and the pain and diarrhea may cause them to
withdraw from normal activities. These patients need to
work with their physicians to find the best combination
of medicine, diet, counseling, and support to control their
symptoms.
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- Scanlon,
D, Becnel, B. Wellness Book of IBS. New York:
St. Martin's Press, 1989. Practical patient's guide
to coping with IBS written by a registered dietitian.
Available in libraries and bookstores.
- Shimberg,
E. Relief From IBS. New York: M. Evans and Company,
1988. Practical book for patients offers information
about IBS symptoms, diet, treatment, and self-care.
Available in libraries and bookstores.
- Steinhart,
MJ. Irritable bowel syndrome: How to relieve symptoms
enough to improve daily function. Postgraduate Medicine
1992; 91(6): 315-321. Article for primary care physicians
includes information about relief of IBS symptoms. Available
in medical and university libraries.
- Thompson,
WG. Gut reactions: Understanding symptoms of the
digestive tract. New York: Plenum Publishing Corp.,
1989. Clear, concise book by a digestive diseases specialist
gives advice about diagnosis, diet, and treatment of
IBS. Available in libraries and bookstores.
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National Digestive Diseases Information Clearinghouse
2 Information Way
Bethesda, MD 20892-3570
E-mail: mailto:nddic@info.niddk.nih.gov
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NIH Publication No. 97-693
October 1992
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