William C. Shiel Jr., MD, FACP, FACR
William C. Shiel Jr., MD, FACP, FACR
Dr. Shiel received a Bachelor of Science degree with honors from the University of Notre Dame. There he was involved in research in radiation biology and received the Huisking Scholarship. After graduating from St. Louis University School of Medicine, he completed his Internal Medicine residency and Rheumatology fellowship at the University of California, Irvine. He is board-certified in Internal Medicine and Rheumatology.
In this Article
Specific tests of gastrointestinal function
Esophageal motility study
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Functional disorders of the esophagus can be identified with esophageal motility studies (manometry). For these studies, a pressure-sensing tube is swallowed and positioned within the esophagus. Contractions of the esophageal muscle normally cause increases in pressure within the esophagus that can be monitored by the catheter during and between swallows of water. Among the abnormalities that can be seen are abnormally high or abnormally low pressures during swallow-associated contractions and/or during spontaneous contractions unassociated with swallows.
Gastric emptying study and electrogastrogram
Slow emptying of the stomach is a common functional abnormality that can lead to bloating, nausea, and vomiting. Rapid emptying of the stomach is relatively uncommon and can lead to abdominal pain and diarrhea. Both of these abnormalities--slow and rapid emptying--can be identified by a gastric emptying study.
The most common type of emptying study is a nuclear medicine study. In this test, patients drink or eat food labeled with radioactive material. A Geiger counter-like device then is placed over the abdomen and the speed with which the radioactive drink or food empties from the stomach is monitored.
The electrogastrogram (EGG) is like the electrocardiogram (ECG) for the heart. Electrodes that are taped to the upper abdomen monitor the electrical activity generated by the muscle of the stomach. Abnormalities of the electrical rhythm of the stomach frequently are associated with dyspeptic symptoms, particularly nausea and vomiting. EGGs are not commonly available and are considered a research tool.
A barostat is an instrument that is used to measure pressure and determine the compliance (flexibility) of a gastrointestinal organ. Compliance is a term that describes the effect that internal stretching has on the organ. The greater the compliance of an organ, the less there is tension (pressure) generated when the organ is stretched from within.
Compliance is important to the normal function of gastrointestinal organs. For example, as food fills the stomach during a meal, the muscles of the stomach must relax (comply) to accommodate the increasing volume of food. If the stomach does not relax properly, the pressure in the stomach increases abnormally. It is believed that abnormally high pressures within the stomach (due to reduced compliance) can lead to symptoms such as early satiety (the feeling of abdominal fullness or pain after only a small amount of food has been ingested).
The barostat includes a balloon that is placed within a gastrointestinal organ through the mouth or anus. As the balloon is progressively blown up and stretches the organ, the pressure within the organ is measured by the barostat. In this way, abnormal compliance can be identified. Barostats can be placed in the esophagus, stomach, small intestine or colon. Barostatic studies, however, probably should be considered experimental. In fact, barostats and expertise in their use are available in only a limited number of centers.
Small intestinal transit study
Small intestinal transit studies measure the speed with which food travels through the small intestine. In the most common type of transit study, a test meal that has been labeled with a radioactive material is ingested. A Geiger-counter-like device is placed over the abdomen and is used to follow the radioactive material through the small intestine and into the colon. Rapid transit is associated with abdominal pain and diarrhea. Slow transit also may be associated with abdominal pain. Although transit studies are not difficult to conduct, they are not frequently used because experience with their use is not wide-spread. They probably should be considered experimental.
Antro-duodenal motility study
Antro-duodenal motility studies measure the pressures that are generated by the contractions of the muscles of the antrum (outlet) of the stomach and the duodenum. For these studies, a pressure-sensing tube is swallowed or passed through the nose and positioned in the distal (outlet) part of the stomach (the antrum) and the first part of the small intestine (the duodenum). Pressures are measured with the stomach empty and after a test meal. Abnormally high or low pressures as well as uncoordinated contractions can be identified. These abnormalities are believed to be associated with symptoms of dyspepsia. Antro-duodenal motility studies and expertise in their use are not widely available.
Gallbladder emptying studies
Gallbladder emptying studies determine how well the gallbladder empties. Between meals, the gallbladder stores bile that is produced by the liver. After meals, the muscles of the gallbladder contract and squeeze out (empty) most of the bile into the intestine. In the intestine, the bile assists with the digestion of food.
For a gallbladder emptying study, a radioactive material is injected intravenously. The radioactive material is removed from the blood by the liver and accumulates with the bile in the gallbladder. The gallbladder then is stimulated to contract with either a meal or an intravenous injection of a hormone, called cholecystokinin. A Geiger-counter-like device is placed over the abdomen and the speed with which the radioactivity leaves the gallbladder and enters the intestine is monitored. Emptying studies of the gallbladder are widely available since this technology is used for several purposes other than measurement of gallbladder emptying.
It has been suggested that abnormally slow emptying of the gallbladder may be associated with abdominal pain. Unfortunately, however, the studies that support the association between slow gallbladder emptying and symptoms are weak. Moreover, many people have abnormally slow emptying of the gallbladder but no symptoms. For these reasons, abnormal emptying studies of the gallbladder have not been widely accepted for diagnosing functional disorders of the gallbladder. The lack of a clear association between dyspepsia and abnormalities of gallbladder emptying is important since it means that patients with abnormal emptying may not be improved by removal of their gallbladders.
Reviewed by William C. Shiel Jr., MD, FACP, FACR on 4/18/2012
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