A Gastric Emptying Study, or Gastric Emptying Scintigraphy, is a specialized diagnostic test that uses nuclear medicine to evaluate the speed at which food travels from the stomach into the small intestine. This process is known as gastric motility. To perform the test, a small amount of radioactive material, known as a radiotracer, is consumed as part of a meal. A gamma camera then tracks the location and amount of this tracer over several hours. The resulting images allow physicians to precisely measure the rate of stomach emptying.
The Purpose of the Study
Physicians typically order this study when a patient reports persistent upper gastrointestinal symptoms suggesting a problem with the stomach’s muscular function. Common complaints include chronic nausea, unexplained vomiting, bloating, and upper abdominal discomfort. Many patients also experience early satiety, the feeling of being full after consuming only a small amount of food. These symptoms often remain unexplained by routine tests like endoscopy or ultrasound.
The primary goal of the study is to confirm or rule out a diagnosis of gastroparesis, a condition characterized by abnormally delayed stomach emptying. When the muscular contractions that move food forward are weakened or absent, food remains in the stomach for too long. This delay can lead to poor nutrient absorption, weight loss, and difficulty managing blood sugar levels in individuals with diabetes.
The test is also useful in identifying conditions where the stomach empties too quickly, such as dumping syndrome. This rapid transit of food, especially after gastric surgery, can cause symptoms including lightheadedness, fast heart rate, and diarrhea shortly after eating. By quantifying the rate of emptying, the study helps distinguish between these different motility disorders. The objective data provided guides appropriate dietary changes and medication selection.
Preparing for and Undergoing the Test
Proper preparation is mandatory to ensure the accuracy and reliability of the test results, as various factors can alter the rate of gastric emptying. Patients are required to fast for a minimum of four to twelve hours before the scheduled appointment. Certain medications that affect gastric motility must also be temporarily discontinued, typically for 48 to 72 hours before the test.
These restricted medications often include opioid pain relievers, prokinetic agents like metoclopramide, and certain diabetic medications that slow the digestive tract. Patients with insulin-dependent diabetes must consult their physician about adjusting their morning insulin dose, as the test meal contains carbohydrates. They are instructed to bring their insulin and glucose monitor for monitoring throughout the procedure.
The procedure begins when the patient consumes a standardized solid meal, often scrambled egg whites or oatmeal mixed with the radiotracer, Technetium-99m sulfur colloid. The meal also includes items like toast and water, and it must be eaten completely within a ten-minute window to establish a precise starting point for the measurement. Immediately after the meal is finished, the patient is positioned beneath a gamma camera.
The camera detects the gamma rays emitted by the radiotracer and begins taking the first set of images to record the initial amount of food in the stomach. Subsequent scans are taken at timed intervals, typically at one, two, and four hours after the meal’s completion. During the scanning periods, the patient must remain still to prevent blurring of the images. Between the scans, the patient is allowed to leave the imaging room but must remain at the facility for the entire four-hour duration of the test.
Understanding the Results
The results are quantified by calculating the percentage of the radiolabeled meal that remains in the stomach at each timed imaging point. These percentages are compared against established reference ranges to determine if the emptying rate is normal, delayed, or rapid. The most informative measurement is the percentage of food retained in the stomach at the end of the four-hour period.
A stomach emptying normally will retain less than ten percent of the meal at the four-hour mark. If the stomach retains more than ten percent of the meal at four hours, or more than sixty percent at two hours, the result indicates delayed gastric emptying, confirming gastroparesis. Conversely, retaining less than thirty percent of the meal after only one hour suggests rapid gastric emptying, or dumping syndrome.
The report may also include a calculation of the gastric “half-time” (\(T_{1/2}\)), which is the number of minutes it takes for half of the meal to exit the stomach. While this number simplifies reporting, the retention percentages at the two- and four-hour intervals remain the standard for diagnosis. An abnormal result provides the clinical evidence needed to begin treatment, which often involves dietary modifications, changes to existing medications, or the introduction of pro-motility drugs.