A Gastric Emptying Study (GES), also known as gastric emptying scintigraphy, measures the speed at which food leaves the stomach and moves into the small intestine. This procedure is the standard method for evaluating the stomach’s motility, or coordinated muscle movement. Tracking this movement helps physicians determine if the stomach is emptying too slowly (gastroparesis) or too quickly (dumping syndrome). The test is performed when a patient experiences symptoms like persistent nausea, vomiting, early satiety, or unexplained abdominal bloating. Abnormal motility can interfere with nutrient absorption and disrupt blood sugar levels, especially in patients with diabetes.
Preparing for the Study
Accurate results depend heavily on the patient following specific preparatory instructions. Patients must fast (not eat or drink anything) for a minimum of four to six hours prior to the scan. The procedure is often scheduled in the morning to allow for an overnight fast, ensuring the stomach is completely empty before the test meal. Patients must also avoid smoking, as nicotine affects gastric emptying speed.
A comprehensive medication review with the ordering physician is necessary, as many common drugs interfere with stomach motility and skew results. Medications that speed up motility (prokinetics like metoclopramide) or slow it down (opioids and certain antidepressants) often need to be stopped several days prior. GLP-1 receptor agonists, used for diabetes and weight loss, significantly delay gastric emptying and may need discontinuation for several weeks before the test, depending on the specific drug.
Diabetic patients require careful management of their blood sugar levels throughout preparation and on the day of the test. They are instructed to bring glucose monitoring supplies and may take a modified dose of insulin or oral medication before the test meal. Since the patient spends up to four hours at the facility, wearing comfortable clothes is recommended. Metal objects should be minimized in the clothing worn for the scan.
The Step-by-Step Testing Procedure
The study begins with the patient consuming a standardized meal tagged with a small, safe amount of a radioactive material called a radiotracer. The most common study measures solid food emptying, using a meal of scrambled egg whites mixed with the radiotracer, served with toast, jam, and water. This meal is standardized in fat, protein, and caloric content to ensure consistent testing conditions. Technetium-99m sulfur colloid is the most common radiotracer used, and it does not change the food’s taste.
The patient must eat the entire meal quickly, usually within ten minutes, to establish an accurate starting time. Immediately after finishing, the patient is positioned under a gamma camera, a specialized piece of nuclear medicine equipment. This first image, the Time 0 scan, establishes the initial location of the radiotracer-labeled meal. The camera detects the gamma rays emitted by the radiotracer, converting them into a digital image to track food movement.
Following the initial scan, the patient can move around the facility but must avoid eating, drinking, or strenuous activity. The procedure requires intermittent imaging over the next several hours to monitor the emptying rate. Scans are taken at pre-determined intervals, typically at one, two, and four hours after the meal. The patient must lie or stand still under the camera for a few minutes during each session.
The entire test takes four hours to complete. The final image at the four-hour mark is the most important for diagnosing delayed emptying. The gamma camera often takes images from both the front and back of the abdomen to accurately account for the stomach’s three-dimensional shape. This sequential imaging generates the data necessary to calculate how much of the meal remains in the stomach over time.
Understanding the Results
A computer program analyzes the images collected throughout the four-hour procedure. It calculates the percentage of the radiotracer meal remaining in the stomach at each interval, providing a quantitative measure of emptying function. Results are expressed as gastric retention percentages at the one, two, and four-hour time points.
A normal result indicates the stomach is emptying at a healthy rate. Normal emptying standards require less than 60% of the meal remaining at two hours and less than 10% remaining at the four-hour mark. Emptying slower than these thresholds indicates delayed gastric emptying.
Significantly delayed emptying, defined as more than 10% of the meal remaining after four hours, strongly indicates gastroparesis. This condition is often associated with long-standing diabetes, which damages nerves controlling stomach muscle function, or it may be idiopathic (cause unknown). Conversely, the study can reveal abnormally rapid emptying, or dumping syndrome, if a high percentage (e.g., more than 70%) empties within the first hour.
The specific data generated guides the physician in creating a treatment plan. For delayed emptying, treatment may involve dietary changes or medications to stimulate stomach contractions. The definitive data helps tailor therapeutic strategies to the severity of the motility issue.