Diarrhea is
an increase in the frequency of bowel movements
or a decrease in the form of stool
(greater looseness of stool).
Although changes in frequency of bowel movements
and looseness of stools can vary independently of each other,
changes often occur in both.
Diarrhea needs to be distinguished from four other conditions.
Although these conditions may accompany diarrhea,
they often have different causes and different treatments than diarrhea.
These other conditions are:
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incontinence of stool,
which is the inability to control (delay) bowel movements
until an appropriate time,
for example, until one can get to the toilet
rectal urgency,
which is a sudden urge to have a bowel movement
that is so strong that if a toilet is not immediately available
there will be incontinence
incomplete evacuation,
which is a sensation
that another bowel movement is necessary
soon after a bowel movement,
yet there is difficulty passing further stool the second time
bowel movements immediately after eating a meal
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Diarrhea is caused by
increased water in the stool.
During normal digestion,
food is kept liquid
by the secretion of large amounts of water by the stomach,
upper small intestine, pancreas, and gallbladder.
Food that is not digested
reaches the lower small intestine and colon in liquid form.
Increased amounts of water in stool
can occur if the stomach and/or small intestine secretes too much fluid,
the distal small intestine and colon do not absorb enough water,
or the undigested,
liquid food passes too quickly
through the small intestine and colon
for enough water to be removed.
Of course,
more than one of these abnormal processes
may occur at the same time.
For example,
some viruses, bacteria and parasites
cause increased secretion of fluid,
either by invading and inflaming
the lining of the small intestine
(inflammation stimulates the lining to secrete fluid)
or by producing toxins (chemicals)
that also stimulate the lining to secrete fluid
but without causing inflammation.
Inflammation of the small intestine
and/or colon from bacteria or from ileitis/colitis
can increase the rapidity with which food passes through the intestines,
reducing the time that is available for absorbing water.
Conditions of the colon such as
collagenous colitis
can block the ability of the colon to absorb water.
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Most episodes of diarrhea are mild and of short duration
and do not need to be brought to the attention of a doctor.
The doctor should be consulted when there is:
-High fever (temperature greater than 101 F)
-Moderate or severe abdominal pain or tenderness
-Bloody diarrhea that suggests severe intestinal inflammation
-Diarrhea in persons with serious underlying illness
for whom dehydration may have more serious consequences,
for example, persons with diabetes, heart disease, and AIDS
-Severe diarrhea that shows no improvement after 48 hours.
-Moderate or severe dehydration
-Prolonged vomiting that prevents intake of fluids orally
-Acute diarrhea in pregnant women
because of concern for the health of the fetus
-Diarrhea that occurs during or immediately
after completing a course of antibiotics
because the diarrhea may represent antibiotic-associated infection
with C. difficile that requires treatment
-Diarrhea after returning from developing countries
or from camping in the mountains
because there may be infection
with Giardia (for which there is treatment)
-Diarrhea that develops in patients
with chronic intestinal diseases
such as colitis, or Crohn's disease
because the diarrhea may represent worsening of the underlying disease
or a complication of the disease, both requiring treatment
-Acute diarrhea in an infant or young child
in order to ensure the appropriate use of oral liquids
(type, amount, and rate),
to prevent or treat dehydration,
and to prevent complications of inappropriate use of liquids
such as seizures and abnormal blood electrolytes
-Chronic diarrhea
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Why am I telling you all this?
It is because I have diarrhea right now
and I'm bored.