Irritable Bowel Syndrome (cont.)
What are IBS symptoms?
The primary purpose of the gastrointestinal tract is to digest (break down)
and absorb (take into the blood stream) food. In order to fulfill this purpose,
food must be ground, mixed, and transported through the intestines, where it is
digested and absorbed. In addition, undigested and unabsorbed portions of the
food must be eliminated from the body.
In functional diseases of the gastrointestinal tract, the grinding, mixing,
digestion, and absorption functions are disturbed to only a minor degree. These
functions are essentially maintained, perhaps because of a built-in
over-capacity of the gastrointestinal tract to perform these functions. The most
commonly affected function in these diseases is transportation. In the stomach
and small intestine, the symptoms of slowed transportation are nausea, vomiting,
abdominal bloating (the sensation of abdominal fullness), and abdominal
distention (enlargement). The symptom of rapid transportation usually is
diarrhea. The interpretation
of symptoms, however, may be more complicated than this. For example, let's say
that a person has abnormally rapid emptying of the stomach. The sensing of this
rapid emptying by the intestinal sensory nerves normally brings about a motor
nerve response to slow emptying of the stomach and transportation through the
small intestine. Thus, rapid emptying of the stomach may give rise to symptoms
of slowed transportation.
In the colon, abnormally slowed or rapid transportation results in
constipation or
diarrhea, respectively. In addition, there may be increased amounts of mucus
coating the stool or a sense of incomplete evacuation after a bowel movement.
As discussed previously, normal sensations may be abnormally processed and
perceived. Such an abnormality could result in abdominal bloating and pain.
Abnormally processed sensations from the gastrointestinal organs also might lead
to motor responses that cause symptoms of slowed or rapid transportation.
Slowed transportation of digesting food through the small intestine may be
complicated, for example, by bacterial overgrowth. In bacterial overgrowth,
gas-producing bacteria that are normally restricted to the colon move up into
the small intestine. There, they are exposed to greater amounts of undigested
food than in the colon, which they turn into gas. This formation of gas can
aggravate bloating and/or abdominal distention and result in increased amounts
of flatus (passing gas, or
flatulence) and diarrhea.
The gastrointestinal tract has only a few ways of responding to diseases.
Therefore, the symptoms often are similar regardless of whether the diseases are
functional or non-functional. Thus, the symptoms of both functional and
non-functional gastrointestinal diseases are nausea, vomiting, bloating,
abdominal distention, diarrhea, constipation, and pain. For this reason, when
functional disease is being considered as a cause of symptoms, it is important
that the presence of non-functional diseases be excluded (ruled out). In fact,
the exclusion of non-functional diseases usually is more important in evaluating
patients who are suspected of having functional disease. This is so, in large
part, because the tests for diagnosing functional disease are complex, not
readily available, and often not very reliable. In contrast, the tests for
diagnosing non-functional diseases are widely available and sensitive (able to
diagnose most cases).
Next: What are the complications of IBS? »
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