Indigestion (Dyspepsia, Upset Stomach)
Medical Author:
Jay W. Marks, MD
Medical Editor:
William C. Shiel, Jr., MD, FACP, FACR
What is dyspepsia (indigestion)?
Dyspepsia is one of the most common ailments of the bowel (intestines),
affecting an estimated 20% of persons in the United States. Perhaps only 10% of those
affected actually seek medical attention for their dyspepsia. Dyspepsia is not a
particularly good term for the ailment since it implies that there is "dyspepsia"
or abnormal digestion of food, and this most probably is not the case. In fact,
another common name for dyspepsia is indigestion, which, for the same reason, is
no better than the term dyspepsia! Doctors frequently refer to the condition as
non-ulcer dyspepsia.
Dyspepsia (indigestion) is best described as a functional disease. (Sometimes, it is called
functional dyspepsia.) The concept of functional disease is particularly useful
when discussing diseases of the gastrointestinal tract. The concept applies to
the muscular organs of the gastrointestinal tract-esophagus, stomach, small
intestine, gallbladder, and colon. What is meant by the term, functional, is
that either the muscles of the organs or the nerves that control the organs are
not working normally, and, as a result, the organs do not function normally. The
nerves that control the organs include not only the nerves that lie within the
muscles of the organs but also the nerves of the spinal cord and brain.
Some gastrointestinal diseases can be seen and diagnosed with the naked eye,
such as ulcers of the stomach. Thus, ulcers can be seen at surgery, on x-rays,
and and by endoscopy. Other diseases cannot be seen with the naked eye but can be
seen and diagnosed under the microscope. For example,
gastritis (inflammation
of the stomach) is diagnosed by microscopic examination of biopsies of the
stomach. In contrast, gastrointestinal functional diseases cannot be seen with the
naked eye or with the microscope. In some instances, the abnormal function can
be demonstrated by tests (for example, gastric emptying studies or antro-duodenal
motility studies). However, the tests often are complex, are not widely available, and
do not reliably detect the functional abnormalities. Accordingly, and by
default, functional gastrointestinal diseases are those that involve abnormal
function of gastrointestinal organs in which the abnormalities cannot be seen in
the organs with either the naked eye or the microscope.
Occasionally, diseases that are thought to be functional are ultimately found
to be associated with abnormalities that can be seen. Then, the disease moves
out of the functional category. An example of this would be
Helicobacter pylori (H.
pylori) infection of the stomach. Some patients with mild upper gastrointestinal
symptoms who were thought to have abnormal function of the stomach or intestines
have been found to have stomachs infected with H. pylori. This
infection can be diagnosed under the microscope by identifying the bacterium.
When patients are treated with antibiotics, the H. pylori and symptoms
disappear. Thus, recognition of infections with Helicobacter pylori has removed
some patients' systems from the functional disease category.
The distinction between functional disease and non-functional disease may, in
fact, be blurry. Thus, even functional diseases probably have associated
biochemical or molecular abnormalities that ultimately will be able to be
measured. For example, functional diseases of the stomach and intestines may be
shown ultimately to be associated with reduced or increased levels of normal
chemicals within the gastrointestinal organs, the spinal cord, or the brain.
Should a disease that is demonstrated to be due to a reduced or increased
chemical still be considered a functional disease? I think not. In this
theoretical situation, we can't see the abnormality with the naked eye or the
microscope, but we can measure it. If we can measure an associated or causative
abnormality, the disease probably should no longer be considered functional.
Despite the shortcomings of the term, functional, the concept of a functional
abnormality is useful for approaching many of the symptoms originating from the
muscular organs of the gastrointestinal tract. To repeat, this concept applies
to those symptoms for which there are no associated abnormalities that can be
seen with the naked eye or the microscope.
While dyspepsia is a major functional disease(s), it is important to mention
several other functional diseases. A second major functional disease is the
irritable bowel syndrome, or IBS. The symptoms of IBS are thought to originate
primarily from the small intestine and/or colon. The symptoms of IBS include
abdominal pain that is accompanied by alterations in bowel movements
(defecation), primarily constipation or diarrhea. In fact,
dyspepsia and IBS may be overlapping diseases since up to half of patients with
IBS also have symptoms of dyspepsia. A third distinct functional
disorder is non-cardiac chest pain. This pain may mimic heart pain (angina), but
it is unassociated with heart disease. In fact, non-cardiac chest pain is
thought to result from a functional abnormality of the esophagus.
Functional disorders of the gastrointestinal tract often are
categorized by the organ of involvement. Thus, there are functional disorders of
the esophagus, stomach, small intestine, colon, and gallbladder. The amount of
research that has been done with functional disorders is greatest in the
esophagus and stomach (for example, non-cardiac chest pain, dyspepsia), perhaps because
these organs are easiest to reach and study. Research into functional disorders
affecting the small intestine and colon (IBS) is more difficult to conduct and
there is less agreement among the research studies. This probably is a
reflection of the complexity of the activities of the small intestine and colon
and the difficulty in studying these activities. Functional diseases of the
gallbladder (referred to as biliary dyskinesia), like those of the small
intestine and colon, also are more difficult to study, and at present they are
less well-defined. Each of the functional diseases is associated with its own
set of characteristic symptoms.
Next: What are the symptoms of dyspepsia
(indigestion)? »
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