Gastroparesis (cont.)
What causes gastroparesis?
Gastroparesis can be caused either by diseases of the
stomach's muscles or the nerves that control the muscles, though often no
specific cause is identified. The most common disease causing gastroparesis is
diabetes mellitus
which damages the nerves controlling the stomach muscles. Gastroparesis also can
also result from damage to the vagus nerve, the nerve
that controls the stomach's muscles, that occurs during surgery on the esophagus and stomach.
Scleroderma is an example of a disease in which gastroparesis is due to damage
to the stomach's muscles. Occasionally, gastroparesis is caused by nervous
reflexes, for example, when the pancreas is inflamed (pancreatitis). In such
cases, neither the nerves nor the muscles are diseased, but messages are sent
through nerves from the pancreas to the stomach which prevents the muscles from
working normally.
Other causes of gastroparesis include imbalances of
minerals in the blood such as potassium, calcium or magnesium, medications (such as
narcotic
pain-relievers), and thyroid disease.
Gastroparesis can occur as an isolated problem or it can
be associated with paralysis of other parts of the intestine, including the
esophagus, small intestine, and colon.
How is gastroparesis diagnosed?
The most common method for diagnosing gastroparesis is a nuclear medicine test
called a gastric emptying study which measures the emptying of food from the
stomach. For this study, a patient eats a meal in which the solid food,
liquid food, or both contain a small amount of radioactive material. A scanner
(acting like a Geiger counter) is placed over the stomach for several hours to
monitor the amount of radioactivity in the stomach. In patients with
gastroparesis, the food takes longer than normal (usually more than several
hours) to empty into the intestine.
The antro-duodenal motility study is a study that can be
considered experimental that is reserved for selected patients. An
antro-duodenal motility study measures the pressure that is generated by the
contractions of the muscles of the stomach and intestine. This study is
conducted by passing a thin tube through the nose, down the esophagus, through
the stomach and into the small intestine. With this tube, the strength of the
contractions of the muscles of the stomach and small intestine can be measured
at rest and following a meal. In most patients with gastroparesis, food (which
normally causes the stomach to contract vigorously) causes either infrequent
contractions (if the nerves are diseased) or only very weak contractions (if the
muscle is diseased). An electrogastrogram, another experimental study that
sometimes is done in patients with suspected gastroparesis, is similar to an
electrocardiogram (EKG) of the heart. The electrogastrogram is a recording of
the electrical signals that travel through the stomach muscles and control the
muscles' contractions. An electrogastrogram is performed by taping several
electrodes onto a patient's abdomen over the stomach area in the same manner as
electrodes are placed on the chest for an EKG. The electrical signals are
recorded at rest and after a meal. In normal individuals, there is a regular
electrical rhythm just as in the heart, and the power (voltage) of the
electrical current increases after the meal. In most patients with
gastroparesis, the rhythm is not normal or there is no increase in electrical
power after the meal. Although the gastric emptying study is the primary test
for diagnosing gastroparesis, there are patients with gastroparesis who have a
normal gastric emptying study but an abnormal electrogastrogram. Therefore, the
electrogastrogram is useful clinically primarily when the suspicion for
gastroparesis is high but the gastric emptying study is normal or borderline
abnormal.
A physical obstruction to the emptying of the stomach,
for example, a tumor that compresses the outlet from the stomach or scarring
from an ulcer, may cause symptoms that are similar to gastroparesis. Therefore,
an upper gastrointestinal (GI) endoscopy test usually is performed to exclude
the possibility of an obstruction as the cause of a patient's symptoms. (Upper
GI endoscopy involves the swallowing of a tube with a camera on the end and can
be used to visually examine the stomach and duodenum and take biopsies.)
Upper GI
endoscopy also may be useful for diagnosing one of the complications of
gastroparesis, a bezoar. Because of the poor emptying of the stomach, hard to
digest components of the diet, usually from vegetables, are retained and
accumulate in the stomach. A ball of undigested, plant-derived material can
accumulate in the stomach and give rise to symptoms of fullness or can further
obstruct the emptying of food from the stomach. Removing the bezoar may improve
symptoms and emptying.
A computerized tomographic (CT) scan
of the abdomen and
upper gastrointestinal x-ray series may also
be necessary to exclude cancer of
the pancreas or other conditions that can obstruct the emptying of the stomach.
Next: How is gastroparesis treated? »
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