A gastric emptying study (GES) is a specialized nuclear medicine test that measures the speed at which food moves from the stomach into the small intestine. This non-invasive procedure evaluates the stomach’s motility to determine if it is functioning within a normal time range. GES is the standard method for diagnosing conditions that affect food processing, most notably gastroparesis, a disorder characterized by delayed gastric emptying. The results provide quantitative data on the rate of stomach clearance, guiding the diagnosis and management of symptoms such as persistent nausea, vomiting, and unexplained fullness after eating.
Preparing for the Study
Accurate test results rely on the patient’s adherence to specific preparation instructions. Patients are required to fast for six to twelve hours prior to their scheduled appointment time, ensuring the stomach is completely empty before the study begins.
Temporary adjustments to medications that influence gut motility are important. Drugs such as opioids, prokinetics, and certain antidepressants may need to be discontinued for up to 48 hours before the test to avoid skewing the emptying rate. Patients with diabetes must coordinate closely with their physician, as blood sugar levels must be monitored and controlled within a specific range, since high blood glucose can slow down gastric emptying.
Patients are also advised to wear comfortable, loose-fitting clothing and remove any metal objects, such as jewelry or belts, that could interfere with the imaging equipment. Smoking is discouraged for several hours before the test and throughout the entire procedure, as nicotine can also affect the stomach’s motility.
Step-by-Step Guide to the Procedure
The gastric emptying study begins with the patient consuming a standardized test meal. This meal typically consists of a solid food, such as scrambled egg whites or oatmeal, mixed with a small, harmless amount of a radioactive tracer, usually Technetium-99m sulfur colloid. The tracer is tasteless and chemically bound to the food, allowing it to be tracked as it moves through the digestive tract.
The patient must consume the entire meal quickly, ideally within ten minutes, to ensure the test starts uniformly. Immediately after the meal is finished, the first image is captured using a specialized gamma camera. This camera is positioned over the abdomen to detect the gamma rays emitted by the tracer, establishing the baseline image.
Following the initial scan, the patient remains at the testing facility for the next several hours as a series of images are taken. Scans are performed at set intervals, typically one hour, two hours, and four hours after the meal ingestion. The patient may move around between scans but must remain relatively still during the actual imaging, which usually takes only a few minutes each time.
The entire procedure usually takes approximately four hours to complete. The purpose of these repeated scans is to measure the progressive reduction in the amount of radioactive tracer remaining in the stomach over time, creating a time-activity curve that represents the rate of gastric emptying.
Interpreting the Study Results
The medical team interprets the study by calculating the percentage of the radioactive tracer that remains in the stomach at each time checkpoint. This quantitative data determines whether the patient’s gastric emptying is normal, delayed, or rapid. The standardized protocol requires a four-hour study to achieve the highest accuracy in diagnosis.
A normal outcome means that less than 10% of the meal’s radioactivity remains in the stomach after four hours. Delayed gastric emptying (gastroparesis) is suggested if more than 60% of the meal is still present at two hours, or if more than 10% remains at the four-hour mark.
Conversely, rapid gastric emptying, often associated with dumping syndrome, is indicated if the stomach empties too quickly, such as less than 70% of the meal remaining after only 30 minutes. The results provide the physician with objective evidence of a motility disorder and its severity, which is then used to formulate a treatment plan.