Constipation (cont.)
What causes constipation?
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
A frequently over-looked cause of constipation is medications.
The most common offending medications include:
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 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.
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
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:
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
A few 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.
Next: How is constipation evaluated? »
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