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Nuclear Scans

By Walter W. Chan, MD, MPH, Assistant Professor of Medicine, Harvard Medical School; Director, Center for Gastrointestinal Motility, Division of Gastroenterology, Hepatology, and Endoscopy, Brigham and Women's Hospital

Nuclear scans are tests that involve the use of harmless radioactive materials (see Radionuclide Scanning). The radioactive materials are ingested as part of a meal or in a drink or are given by vein (intravenously). The small amount of radiation produced by these materials is used to produce images of internal structures. After the materials are in the body, doctors use a special radiation-sensing scanner or camera, called a gamma camera, to show where the materials are in the body. Different types of scans with different nuclear materials are used depending on the purpose of the test and which part of the body needs to be imaged.

A gastric emptying scan is done to determine how quickly the stomach empties. People whose stomach empties poorly or slowly have a disorder called gastroparesis, which may cause symptoms such as nausea, vomiting, or a feeling of fullness after eating a small meal. For this scan, people drink a beverage or eat a meal that contains a small amount of radioactive material. Doctors then use a gamma camera to observe how quickly the material passes out of the stomach. The camera can show whether people have gastroparesis or a blockage. Because this test cannot show the difference between a blockage and gastroparesis, further tests are done if stomach emptying is delayed. This scan can also help doctors monitor how well people are responding to promotility drugs. These drugs, such as metoclopramide and erythromycin, stimulate the movement of contents through the stomach and intestines.

A bleeding scan is sometimes done to determine the location of bleeding in the digestive tract. For this scan, radioactive material is attached to red blood cells or other material that is injected into the bloodstream. The gamma camera can show the part of the abdomen where the radioactive-labeled cells are leaking out of the intestine, suggesting the location of the bleeding. This scan is useful mainly for people who have brisk bleeding in the digestive tract and who are not good candidates for endoscopy.

A Meckel scan is done to identify problems in the small intestine, such as a Meckel diverticulum (see Meckel Diverticulum). For this test, radioactive material is injected into a vein. The substance is picked up by cells in the wall of the Meckel diverticulum, which can then be seen using a gamma camera.