What is a gastric emptying study?
Abdominal pain can be a symptom of slow gastric emptying.
The most common type of gastric emptying study is a procedure that is done by nuclear medicine
physicians using radioactive chemicals
that measures the speed with which food empties from the stomach and enters the small intestine. Gastric emptying studies are used for
evaluating patients who are having symptoms that may be due to slow and, less commonly, rapid emptying of the stomach. The symptoms of slow emptying are primarily nausea, vomiting,
abdominal pain, and abdominal fullness after eating. The symptoms of rapid emptying are diarrhea, weakness, or light-headedness after eating.
How is a gastric emptying study done?
For a gastric emptying study, a patient eats a meal in which the solid component of the meal (for example, scrambled eggs or oatmeal for vegetarians), the liquid component of the meal (for example, water), or both, are mixed with a small amount of radioactive material. A scanner (acting like a Geiger counter) is placed over the patient's stomach to monitor the amount of radioactivity in the stomach for several hours after the test meal is eaten. As the radioactively-labeled food empties from the stomach, the amount of radioactivity in the stomach decreases. The rate at which the radioactivity leaves the stomach reflects the rate at which food is emptying from the stomach
Some medications such as narcotic pain relievers and anticholinergic medications can cause a delay in emptying of the stomach, while other medications such as metoclopramide (Reglan) and erythromycin can cause rapid emptying of the stomach. Medications that slow emptying of the stomach can give a falsely abnormal test result, while medications that speed up emptying of the stomach can give a falsely normal result. Therefore, medications that affect emptying of the stomach should be withheld for 72 hours before performing emptying studies.
Abnormally high blood glucose (sugar) levels also can slow emptying of the stomach. Therefore, it is important to control blood glucose levels to near normal levels before performing emptying studies in people with diabetes who are prone to develop high blood glucose levels.
When is a gastric emptying study used?
A gastric emptying study often is used when there is a
suspicion that there is an abnormally delayed emptying of food from the stomach,
medically called delayed gastric emptying. Delayed gastric emptying most
commonly gives rise to abdominal discomfort after meals, nausea and vomiting. The two most common
causes of delayed gastric emptying are gastric outlet obstruction and
gastroparesis.
Gastric outlet
obstruction refers to
a condition in which the narrow channel leading from the stomach into the small
intestine through which food passes
(called the pylorus) is physically blocked, and, as a result food enters the
first part of the small intestine (called the duodenum) slowly or not
at all. The most common causes of gastric outlet obstruction are scarring or
inflammation of the pylorus from peptic ulcers,
cancers of the stomach, or,
occasionally, cancers near the pylorus, for example, of the
pancreas or
duodenum. A diagnosis of gastric outlet obstruction is made by tests such as
esophagogastroduodenoscopy (EGD), abdominal computerized tomography (CT scan),
and upper GI series.
Once gastric outlet obstruction has been excluded by
appropriate testing as the cause of delayed gastric emptying, physicians then
may perform a gastric emptying study to diagnose gastroparesis. Gastroparesis is
a condition in which there is delayed gastric emptying, but the delay is not due
to obstruction. Rather, it is due to abnormal function of the muscles of the
stomach. Normal function of the stomach’s muscles is necessary in order to
propel food from the stomach and into the small intestine. If the muscles or the
nerves that control the muscles are not working normally, food remains in the
stomach. Gastroparesis is commonly caused by diseases and medications. The most
common cause of gastroparesis is diabetes mellitus, which affects the function
of the stomach's nerves and muscles. Many cases of gastroparesis have no clear
cause for the dysfunction. These cases are referred to as idiopathic
gastroparesis.
A gastric emptying study also may be used when there is
a suspicion that there is abnormally rapid gastric emptying. Rapid gastric
emptying can cause diarrhea and episodes of weakness or light-headedness
following meals (referred to as the “dumping” syndrome). Common causes of rapid
gastric emptying include surgery of the stomach and diabetes mellitus.
How are the results of a gastric emptying study evaluated?
In patients with gastroparesis, the food and the attached radioactive
material remain in the stomach longer than normal (usually hours) before
emptying into the small intestine. As a result, the scanner continues to show
radioactivity in the area of the stomach for hours after the test meal. If
abnormally slow emptying is demonstrated, medications such as metoclopramide
(Reglan) may be given to speed up the emptying and improve symptoms. If
abnormally rapid emptying of the stomach is found, medications may be given to
slow down emptying.
Are there any side effects of a gastric emptying study?
There are no side effects from a gastric emptying
study. The radioactive material is not absorbed into the body and is eliminated
in the stool. Nevertheless, gastric emptying studies as well as any other studies that
utilize radioactive materials should not be performed in
pregnant women because
the fetus is exposed to some radioactivity.
Are there other tests that can be performed instead of a gastric emptying study?
An upper gastrointestinal (GI) series X-ray demonstrates abnormal emptying of barium in patients with a severe emptying problem, however, it cannot diagnose abnormal emptying of a mild or moderate degree. An antro-duodenal motility study or an electrogastrogram can demonstrate abnormalities in the muscles and nerves of the stomach, but they do not directly evaluate the effects of these abnormalities on emptying of the stomach. Other experimental methods for evaluating emptying of the stomach have been described, for example, ultrasonography, breath tests using fatty acids, and single photon emission computerized tomography (SPECT) but these tests are available in very few centers.
