Constipation
Constipation means different things to different people. For many people, it
simply means infrequent stools. For others, however, constipation means
hard stools, difficulty passing stools (straining), or a sense of incomplete
emptying after a bowel movement. The cause of each of these "types" of
constipation probably is different, and the approach to each should be
tailored to the specific type of constipation.
Constipation also can alternate with diarrhea. This pattern commonly
occurs as part of the irritable bowel syndrome (IBS). At the extreme end of
the constipation spectrum is fecal impaction, a condition in which stool
hardens in the rectum and prevents the passage of any stool.
The number of bowel movements generally decreases with age. Ninety-five
percent of adults have bowel movements between three and 21 times per
week, and this would be considered normal. The most common pattern is
one bowel movement a day, but this pattern is seen in less than 50% of
people. Moreover, most people are irregular and do not have bowel
movements every day or the same number of bowel movements each day.
Medically speaking, constipation usually is defined as fewer than three
bowel movements per week. Severe constipation is defined as less than
one bowel movement per week. There is no medical reason to have a
bowel movement every day. Going without a bowel movement for two or
three days does not cause physical discomfort, only mental distress for
some people. Contrary to popular belief, there is no evidence that "toxins"
accumulate when bowel movements are infrequent or that constipation
leads to cancer.
It is important to distinguish acute (recent onset) constipation from chronic
(long duration) constipation. Acute constipation requires urgent
assessment because a serious medical illness may be the underlying
cause (for example, tumors of the colon). Constipation also requires an
immediate assessment if it is accompanied by worrisome symptoms such
as rectal bleeding, abdominal pain and cramps, nausea and vomiting, and
involuntary loss of weight. In contrast, the evaluation of chronic constipation
may not be urgent, particularly if simple measures bring relief.
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Theoretically, constipation can be caused by the slow passage of digesting
food through any part of the intestine. More than 95% of the time, however,
the slowing occurs in the colon.
Medications that cause constipation
A frequently over-looked cause of constipation is medications. The most
common offending medications include:

Narcotic pain medications such as codeine (for example, Tylenol #3),
oxycodone (for example, Percocet), and hydromorphone (Dilaudid);

Antidepressants such as amitriptyline (Elavil) and imipramine (Tofranil)

Anticonvulsants such as phenytoin (Dilantin) and carbamazepine
(Tegretol)

Iron supplements

Calcium channel blocking drugs such as diltiazem (Cardizem) and
nifedipine (Procardia)

Aluminum-containing antacids such as Amphojel and Basaljel
In addition to the medications listed above, there are many others that can
cause constipation. Simple measures (for example, increasing dietary fiber)
for treating the constipation caused by medications are often are effective,
and discontinuing the medication is not necessary. If simple measures
don't work, it may be possible to substitute a less constipating medication.
For example, a nonsteroidal antiinflammatory drug (for example, ibuprofen)
may be substituted for narcotic pain medications. Additionally, one of the
newer and less constipating anti-depressant medications [for example,
fluoxetine (Prozac)] may be substituted for amitriptyline and imipramine.
Other causes of constipation
Habit
Bowel movements are under voluntary control. This means that the normal
urge people feel when they need to have a bowel movement can be
suppressed. Although occasionally it is appropriate to suppress an urge to
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defecate (for example, when a bathroom is not available), doing this too
frequently can lead to a disappearance of urges and result in constipation.
Diet
Fiber is important in maintaining a soft, bulky stool. Diets that are low in
fiber can, therefore, cause constipation. The best natural sources of fiber
are fruits, vegetables, and whole grains.
Laxatives
One suspected cause of severe constipation is the over-use of stimulant
laxatives [for example, senna (Senokot), castor oil, and certain herbs]. An
association has been shown between the chronic use of stimulant laxatives
and damage to the nerves and muscles of the colon, and it is believed by
some that the damage is responsible for the constipation. It is not clear,
however, whether the laxatives have caused the damage or whether the
damage existed prior to the use of laxatives and, indeed, has caused the
laxatives to be used. Nevertheless, because of the possibility that stimulant
laxatives can damage the colon, most experts recommend that stimulant
laxatives be used as a last resort after non-stimulant treatments have
failed.
Hormonal disorders
Hormones can affect bowel movements. For example:

Too little thyroid hormone (hypothyroidism) and too much parathyroid
hormone (by raising the calcium levels in the blood) can cause
constipation.

At the time of a woman's menstrual periods, estrogen and progesterone
levels are high and may cause constipation. However, this is rarely a
prolonged problem.

High levels of estrogen and progesterone during pregnancy also can
cause constipation.
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Diseases that affect the colon
There are many diseases that can affect the function of the muscles and/or
nerves of the colon. These include diabetes, scleroderma, intestinal
pseudo-obstruction, Hirschsprung's disease, and Chagas disease. Cancer
or narrowing (stricture) of the colon that blocks the colon likewise can
cause a decrease in the flow of stool.
Central nervous system diseases
Some diseases of the brain and spinal cord may cause constipation,
including Parkinson's disease, multiple sclerosis, and spinal cord injuries.
Colonic inertia
Colonic inertia is a condition in which the nerves and/or muscles of the
colon do not work normally. As a result, the contents of the colon are not
propelled through the colon normally. The cause of colonic inertia is
unclear. In some cases, the muscles or nerves of the colon are diseased.
Colonic inertia also may be the result of the chronic use of stimulant
laxatives as described above. In most cases, however, there is no clear
cause for the constipation.
Pelvic floor dysfunction
Pelvic floor dysfunction (also known as outlet obstruction or outlet delay)
refers to a condition in which the muscles of the lower pelvis that surround
the rectum (the pelvic floor muscles) do not work normally. These muscles
are critical for defecation (bowel movement). It is not known why these
muscles fail to work properly in some people, but they can make the
passage of stools difficult even when everything else is normal.
What treatments are available for constipation?
There are many treatments for constipation, and the best approach relies
on a clear understanding of the underlying cause.
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Dietary fiber (bulk-forming laxatives)
The best way of adding fiber to the diet is increasing the quantity of fruits
and vegetables that are eaten. This means a minimum of five servings of
fruits or vegetables every day. For many people, however, the amount of
fruits and vegetables that are necessary may be inconveniently large or
may not provide adequate relief from constipation. In this case, fiber
supplements can be useful.
Fiber is defined as material made by plants that is not digested by the
human gastrointestinal tract. Fiber is one of the mainstays in the treatment
of constipation. Many types of fiber within the intestine bind to water and
keep the water within the intestine. The fiber adds bulk (volume) to the
stool and the water softens the stool.
There are different sources of fiber and the type of fiber varies from source
to source. Types of fiber can be categorized in several ways, for example,
by their source.
The most common sources of fiber include:

fruits and vegetables,

wheat or oat bran,

psyllium seed (for example, Metamucil, Konsyl),

synthetic methyl cellulose (for example, Citrucel), and

polycarbophil (for example, Equilactin, Konsyl Fiber).
Polycarbophil often is combined with calcium (for example, Fibercon).
However, in some studies, the calcium-containing polycarbophil was not as
effective as the polycarbophil without calcium.
A lesser known source of fiber is an extract of malt (for example,
Maltsupex); however, this extract may soften stools in ways other than
increasing fiber.
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Increased gas (flatulence) is a common side effect of high-fiber diets. The
gas occurs because the bacteria normally present within the colon are
capable of digesting fiber to a small extent. The bacteria produce gas as a
byproduct of their digestion of fiber. All fibers, no matter what their source,
can cause flatulence. However, since bacteria vary in their ability to digest
the various types of fiber, the different sources of fiber may produce
different amounts of gas. To complicate the situation, the ability of bacteria
to digest one type of fiber can vary from individual to individual. This
variability makes the selection of the best type of fiber for each person (for
example, a fiber that improves the quality of the stool without causing
flatulence) more difficult. Thus, finding the proper fiber for an individual
becomes a matter of trial and error.
The different sources of fiber should be tried one by one. The fiber should
be started at a low dose and increased every one to two weeks until either
the desired effect on the stool is achieved or troublesome flatulence
interferes. (Fiber does not work overnight.) If flatulence occurs, the dose of
fiber can be reduced for a few weeks and the higher dose can then be tried
again. (It generally is said that the amount of gas that is produced by fiber
decreases when the fiber is ingested for a prolonged period of time;
however, this has never been studied.) If flatulence remains a problem and
prevents the dose of fiber from being raised to a level that affects the stool
satisfactorily, it is time to move on to a different source of fiber.
When increasing amounts of fiber are used, it is recommended that greater
amounts of water be consumed (for example, a full glass with each dose).
In theory, the water prevents "hardening" of the fiber and blockage
(obstruction) of the intestine. This seems like simple and reasonable
advice. However, ingesting larger amounts of water has never been shown
to have a beneficial effect on constipation, with or without the addition of
fiber. (There is already a lot of water in the intestine and extra water that is
digested is absorbed and excreted in the urine.) It is reasonable to drink
enough fluids to prevent dehydration because with dehydration there may
be reduced intestinal water.
Because of concern about obstruction, persons with narrowings (strictures)
or adhesions (scar tissue from previous surgery) of their intestines should
not use fiber unless it has been discussed with their physician. Some fiber
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laxatives contain sugar, and patients with diabetes may need to select
sugar-free products.
Lubricant laxatives
Lubricant laxatives contain mineral oil as either the plain oil or an emulsion
(combination with water) of the oil. The oil stays within the intestine, coats
the particles of stool, and presumably prevents the removal of water from
the stool. This retention of water in the stool results in softer stool. Mineral
oil generally is used only for the short-term treatment of constipation since
its long-term use has several potential disadvantages.
The oil can absorb fat-soluble vitamins from the intestine and, if used for
prolonged periods, may lead to deficiencies of these vitamins. This is of
particular concern in pregnancy during which an adequate supply of
vitamins is important for the fetus. In the very young or very elderly in
whom the swallowing mechanism is not strong or is impaired by strokes,
small amounts of the swallowed oil may enter the lungs and cause a type
of pneumonia called lipid pneumonia. Mineral oil also may decrease the
absorption of some drugs such as warfarin (Coumadin) and oral
contraceptives, thereby decreasing their effectiveness. Despite these
potential disadvantages, mineral oil can be effective when short-term
treatment is necessary.
Emollient laxatives (stool softeners)
Emollient laxatives are generally known as stool softeners. They contain a
compound called docusate (for example, Colace). Docusate is a wetting
agent that improves the ability of water within the colon to penetrate and
mix with stool. This increased water within the stool softens the stool.
Although studies have not shown docusate to be consistently effective in
relieving constipation. Stool softeners often are used in the long-term
treatment of constipation. It may take a week or more for docusate to be
effective. The dose should be increased after one to two weeks if no effect
is seen.
Although docusate generally is safe, it may increase the absorption of
mineral oil and some medications from the intestine. Absorbed mineral oil
collects in tissues of the body, for example, the lymph nodes and the liver,
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where it causes inflammation. It is not clear if this inflammation has any
important consequences, but it generally is felt that prolonged absorption of
mineral oil should not be allowed. The use of emollient laxatives is not
recommended together with mineral oil or with certain prescription
medications. Emollient laxatives are commonly used when there is a need
to soften the stool temporarily and make defecation easier (for example,
after surgery, childbirth, or heart attacks). They are also used for individuals
with hemorrhoids or anal fissures.
Hyperosmolar laxatives
Hyperosmolar laxatives are undigestible, unabsorbable compounds that
remain within the colon and retain the water that already is in the colon.
The result is softening of the stool. The most common hyperosmolar
laxatives are lactulose (for example, Kristalose), sorbitol, and polyethylene
glycol (for example, MiraLax). and are available by prescription only. These
laxatives are safe for long-term use and are associated with few side
effects.
Hyperosmolar laxatives may be digested by colonic bacteria and turned
into gas, which may result in unwanted abdominal bloating and flatulence.
This effect is dose-related and less with polyethylene glycol. Therefore, gas
can be reduced by reducing the dose of the laxative. In some cases, the
gas will decrease over time.
Saline laxatives
Saline laxatives contain non-absorbable ions such as magnesium, sulfate,
phosphate, and citrate [for example, magnesium citrate (Citroma),
magnesium hydroxide, sodium phosphate). These ions remain in the colon
and cause water to be drawn into the colon. Again, the effect is softening of
the stool.
Magnesium also may have mild stimulatory effects on the colonic muscles.
The magnesium in magnesium-containing laxatives is partially absorbed
from the intestine and into the body. Magnesium is eliminated from the
body by the kidneys. Therefore, individuals with impaired kidney function
may develop toxic levels of magnesium from chronic (long duration) use of
magnesium-containing laxatives.
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Saline laxatives act within a few hours. In general, potent saline laxatives
should not be used on a regular basis. If major diarrhea develops with the
use of saline laxatives and the lost fluid is not replaced by the consumption
of liquids, dehydration may result. For constipation, the most frequentlyused and mildest of the saline laxatives is milk of magnesia. Epsom Salt is
a more potent saline laxative that contains magnesium sulfate.
Stimulant laxatives
Stimulant laxatives cause the muscles of the small intestine and colon to
propel their contents more rapidly. They also increase the amount of water
in the stool, either by reducing the absorption of the water in the colon or by
causing active secretion of water in the small intestine.
The most commonly-used stimulant laxatives contain cascara (castor oil),
senna (for example, Ex-Lax, Senokot), and aloe. Stimulant laxatives are
very effective, but they can cause severe diarrhea with resulting
dehydration and loss of electrolytes (especially potassium). They also are
more likely than other types of laxatives to cause intestinal cramping. There
is concern that chronic use of stimulant laxatives may damage the colon
and worsen constipation, as previously discussed. Bisacodyl (for example,
Dulcolax, Correctol) is a stimulant laxative that affects the nerves of the
colon which, in turn, stimulate the muscles of the colon to propel its
contents. Prunes also contain a mild colonic stimulant.
Enemas
There are many different types of enemas. By distending the rectum, all
enemas (even the simplest type, the tap water enema) stimulate the colon
to contract and eliminate stool. Other types of enemas have additional
mechanisms of action. For example, saline enemas cause water to be
drawn into the colon. Phosphate enemas (for example, Fleet phosphosoda)
stimulate the muscles of the colon. Mineral oil enemas lubricate and soften
hard stool. Emollient enemas (for example, Colace Microenema) contain
agents that soften the stool.
Enemas are particularly useful when there is impaction, which is hardening
of stool in the rectum. In order to be effective, the instructions that come
with the enema must be followed. This requires full application of the
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enema, appropriate positioning after the enema is instilled, and retention of
the enema until cramps are felt. Defecation usually occurs between a few
minutes and one hour after the enema is inserted.
Enemas are meant for occasional rather than regular use. The frequent use
of enemas can cause disturbances of the fluids and electrolytes in the
body. This is especially true of tap water enemas. Soapsuds enemas are
not recommended because they can seriously damage the rectum.
Suppositories
As is the case with enemas, different types of suppositories have different
mechanisms of action. There are stimulant suppositories containing
bisacodyl (for example, Dulcolax). Glycerin suppositories are believed to
have their effect by irritating the rectum. The insertion of the finger into the
rectum when the suppository is placed may itself stimulate a bowel
movement.
Combination products
There are many products that combine different laxatives. For example,
there are oral products that combine senna and psyllium (Perdiem), senna
and docusate (Senokot-S), and senna and glycerin (Fletcher's Castoria).
One product even combines three laxatives, senna-like casanthranol,
docusate, and glycerin (Sof-lax Overnight). These products may be
convenient and effective, but they also contain stimulant laxatives.
Therefore, there is concern about permanent colonic damage with the use
of these products, and they probably should not be used for long-term
treatment unless non-stimulant treatment fails.
Miscellaneous drugs
Several prescribed drugs that are used to treat medical diseases
consistently cause (as a side effect) loose stools, even diarrhea. There
actually are several small studies that have examined these drugs for the
treatment of constipation.
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Exercise
People who lead sedentary lives are more frequently constipated than
people who are active. Nevertheless, limited studies of exercise on bowel
habit have shown that exercise has minimal or no effect on the frequency
of bowel movements. Thus, exercise can be recommended for its many
other health benefits, but not for its effect on constipation.
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