If your doctor suspects gastroparesis, the next step is a gastric emptying study. This is the gold standard test for measuring how quickly food leaves your stomach. It is noninvasive, widely available, and provides objective data that symptoms and endoscopy cannot. Yet many patients arrive at this test with no idea what to expect, how to prepare, or how to interpret the results they receive. This guide covers every step, from preparation through interpretation, so you can approach the test informed and know what your results actually mean.
What is a gastric emptying study?
A gastric emptying study, formally called gastric emptying scintigraphy (GES), is a nuclear medicine test. You eat a standardized meal that contains a small amount of radioactive tracer (technetium-99m sulfur colloid mixed into egg whites). A gamma camera then takes images of your abdomen at set intervals, typically at 0, 1, 2, and 4 hours after eating, to measure how much of the meal remains in your stomach over time. The radioactive tracer is safe, with radiation exposure comparable to a standard chest X-ray. The test is performed in a hospital or outpatient nuclear medicine department.
How to prepare for the test
- Stop medications that affect gastric motility. Your doctor will provide specific instructions, but generally: prokinetics (metoclopramide, domperidone, erythromycin) should be stopped 48-72 hours before the test. Opioids should be stopped 48 hours before. GLP-1 receptor agonists (semaglutide, tirzepatide) may need to be held for longer due to their extended half-life. Anticholinergics should be stopped 48 hours before.
- Fast for at least 8 hours before the test, ideally overnight. Do not eat or drink anything (including water in some protocols) after midnight the night before a morning test.
- Check your blood glucose if you have diabetes. Hyperglycemia (blood glucose above 275 mg/dL) slows gastric emptying independently and can produce a falsely abnormal result. Some centers will reschedule if glucose is too high on test day.
- Avoid smoking on the morning of the test. Nicotine can alter gastric motility and affect results.
- Wear comfortable clothing. You will be sitting or standing near a gamma camera for brief imaging sessions over 4 hours.
What happens during the 4-hour study
The test begins when you eat the standardized meal. The American Neurogastroenterology and Motility Society consensus protocol specifies: two egg whites mixed with technetium-99m sulfur colloid (cooked as scrambled eggs or egg substitute), two slices of white bread, 30 grams of strawberry jam, and 120 mL of water. You must eat the entire meal within 10 minutes. This standardization is important because the test was validated against this specific meal, and different foods empty at different rates.
After eating, you will sit or stand in front of the gamma camera for an initial image (time zero). You then return for images at 1 hour, 2 hours, and 4 hours. Each imaging session takes about 1-2 minutes. Between imaging sessions, you wait in the department. You should not eat, drink, or lie down during the test period, as these can alter results. Some facilities allow you to leave between sessions and return, while others ask you to stay. Total time commitment is approximately 4.5-5 hours including meal preparation and imaging.
How to read your results
Results are reported as percentage of the meal retained in the stomach at each time point. The key diagnostic measurement is the 4-hour retention value. Normal gastric emptying: less than 90% retained at 1 hour, less than 60% retained at 2 hours, and less than 10% retained at 4 hours. The 4-hour value is the most clinically important. Greater than 10% retention at 4 hours is the established diagnostic threshold for gastroparesis.
- Normal: less than 10% retention at 4 hours. The stomach is emptying at a normal rate.
- Mild gastroparesis: 10-15% retention at 4 hours. Gastric emptying is delayed but modestly so. Symptoms may be intermittent.
- Moderate gastroparesis: 15-35% retention at 4 hours. Significant delay in emptying that typically produces consistent symptoms.
- Severe gastroparesis: greater than 35% retention at 4 hours. Markedly delayed emptying with high symptom burden and elevated risk of complications including SIBO, bezoar formation, and nutritional deficiency.
âšī¸Ask your doctor for the actual retention percentages at each time point, not just a "normal" or "abnormal" label. A result of 11% retention at 4 hours (borderline delayed) has very different clinical implications than 45% retention (severely delayed), even though both are technically "abnormal."
Why endoscopy does not replace this test
Many patients with suspected gastroparesis undergo upper endoscopy (EGD) first, which is appropriate for ruling out mechanical obstruction, ulcers, and other structural problems. Occasionally, endoscopy reveals retained food in the stomach despite an adequate fasting period, which raises suspicion for gastroparesis. However, endoscopy cannot quantify how fast or slow the stomach empties. A single snapshot of stomach contents does not provide the time-based emptying data that a GES produces. Some patients have food in their stomachs at endoscopy due to anxiety, recent eating, or medication effects without having true gastroparesis. Conversely, a patient with mild gastroparesis may have a clear stomach at endoscopy if they happened to eat lightly the day before. The gastric emptying study is the only test that objectively measures emptying rate over time.
Alternative tests for gastric emptying
While scintigraphy remains the gold standard, two alternatives exist. The wireless motility capsule (SmartPill) is an ingestible capsule that measures pH, pressure, and temperature as it travels through the GI tract. It provides gastric emptying time based on the pH change that occurs when the capsule passes from the acidic stomach to the alkaline duodenum. It also measures small bowel and colonic transit times, making it useful for evaluating whole-gut motility. The 13C-spirulina breath test uses a carbon-13 labeled substrate that is absorbed after leaving the stomach, and the rate of 13C appearance in breath correlates with gastric emptying. This test is less widely available but does not require nuclear medicine facilities.
What to do with your results
If your gastric emptying study confirms gastroparesis, the next steps depend on the severity and suspected cause. For mild gastroparesis, dietary modification (small, frequent, low-fat, low-fiber meals) and prokinetic therapy may be sufficient. For moderate to severe cases, more aggressive prokinetic regimens, antiemetics, and in some cases pyloric interventions (gastric per-oral endoscopic myotomy, or G-POEM) may be considered. Regardless of severity, if you have confirmed gastroparesis and symptoms consistent with SIBO (bloating, diarrhea, brain fog), breath testing for SIBO is the logical next step. Treating SIBO alongside gastroparesis addresses both the cause and the consequence.
â ī¸This article is for educational purposes only and is not a substitute for professional medical advice, diagnosis, or treatment. Always consult a qualified healthcare provider with questions about a medical condition.