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Arnold Wald, MD, MACG, Department of Medicine,
University of Pittsburgh Medical Center, Pittsburgh, PA
Constipation is one of the most frequent gastrointestinal
complaints in the USA and Western countries. There are at
least 2.5 million doctor visits for constipation in the USA
each year and hundreds of millions of dollars are spent for
laxatives yearly.
1. How is constipation defined?
Constipation is often thought of as a decrease in frequency
of stools and many people believe they are constipated if
they do not have a bowel movement each day. This is not correct
as many persons have as few as 3 bowel movements each week
and are healthy. For many people, constipation means too much
straining with bowel movements, passage of small hard stools
or a sense that they have not completely emptied their bowels.
Any recent change in bowel habits, if persistent, may be cause
for concern.
2. What causes constipation?
Constipation most commonly occurs when the waste (stool) that
forms after food is digested moves too slowly (slow transit)
as it passes through the digestive tract. Dehydration, changes
in diet and activity, and certain drugs are frequently to blame
to slow transit of stool. When stool moves slowly, too much
water is absorbed from the stool, and it becomes hard and dry.
Gradual enlargement of the rectum and poor coordination of the
pelvic and anal muscles sometimes contribute to or cause constipation.
Sometimes a combination of these processes occurs. Another cause,
bowel obstruction (blockage), is serious but uncommon. 3.
What kind of evaluation should constipated patients undergo?
A doctor usually relies on the person's account of constipation
when making a diagnosis. The doctor also examines the rectum
with a gloved finger and, if stool is present, determines
the amount and consistency. The stool is tested for occult
(hidden) blood. The person's symptoms and an examination are
often all that are needed to confirm a diagnosis of constipation
and to determine the likely cause.
When the cause remains unclear, tests may be done. The doctor
may recommend an examination with a flexible viewing tube,
either of just the lower part of the large intestine (sigmoidoscopy)
or of the entire large intestine (colonoscopy). This examination
is important if the constipation developed suddenly or if
it is worsening noticeably.
Occasionally, other tests are needed to determine the cause.
An abdominal x-ray may show evidence of bowel obstruction
or suggest another cause. Another test involves swallowing
several capsules containing tiny rings that can be seen on
x-rays. An x-ray is taken several days later. Finally, emptying
of the rectum can be tested in the laboratory or with special
x-rays.
4. What are the treatments for constipation?
When stool is impacted, tap water enemas are commonly used.
Usually people are positioned on their left side, with knees
flexed. About 5 to 10 ounces of water at body temperature
are gently instilled into the rectum and sigmoid colon. When
the water is emptied, the impacted stool is passed with it.
Nonprescription prepackaged enemas can be used in place of
tap water. If enemas fail to work, a health care practitioner
may need to remove the stool manually using a gloved finger.
The person is then sometimes asked to drink a solution containing
dissolved salts and polyethylene glycol, which cleanses the
digestive tract.
After the impaction has been removed, the person may be told
to add fiber to the diet or to use laxatives to prevent constipation.
Laxatives may be used every two to three days if a bowel movement
does not occur naturally.
If the stool is not impacted, several options are available
for treating constipation. Increasing the intake of fluids
and fiber is often the first step. Vegetables, fruit (especially
prunes), whole-grain breads, and high-fiber cereals are excellent
sources of fiber. Bran is an alternative source. To work well,
fiber should be consumed with plenty of fluids.
Laxatives and stool softeners are sometimes needed if changes
in diet are insufficient. Most laxatives are safe for long-term
uses, if used appropriately.
Bulking agents, such as psyllium and methylcellulose, are
laxatives that help hold water in the stool and add bulk to
it. The increased bulk stimulates the natural contractions
of the large intestine. Bulkier stools are softer and easier
to pass. Bulking agents act slowly and gently. These agents
generally are taken in small amounts at first. The dose is
increased gradually until regularity is achieved.
Osmotic agents are laxatives that keep large amounts of water
in the large intestine, making the stool soft and loose. These
laxatives consist of salts or sugars that are poorly absorbed.
Some contain magnesium and phosphate, which can be partially
absorbed resulting in harm to people with kidney failure.
Stimulant laxatives contain substances that directly stimulate
the walls of the large intestine (such as senna, cascara,
and bisacodyl), causing them to contract. Taken by mouth,
stimulant laxatives generally cause a bowel movement in six
to eight hours. Some are available as suppositories. When
taken as suppositories, these laxatives often work in 15 to
60 minutes. Stimulant laxatives are best used for brief periods.
If longer use is needed, they should be used no more often
than every third day and under a doctor's supervision.
Occasionally, a problem with coordination of pelvic floor
and anorectal muscles may be identified. This can be treated
with biofeedback or muscle retraining exercises; such treatments
are performed only in centers which specialize in this area
and upon referral by a doctor.
5. Can constipation be prevented?
A combination of an adequate intake of fluids, adequate exercise,
and a high-fiber diet may prevent constipation. Laxatives
are sometimes a helpful addition to these measures. For example,
when a person needs to take a potentially constipating drug,
a stimulant laxative along with increased intake of dietary
fiber and fluids helps prevent constipation.
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