What Is Gastroparesis?
Gastroparesis is a condition where the stomach takes significantly longer than normal to empty its contents into the small intestine. In a healthy digestive system, the stomach muscles contract in coordinated waves to grind food and push it forward. In gastroparesis, these contractions are weak or uncoordinated, causing food to sit in the stomach for hours longer than it should.
The most common cause of gastroparesis is diabetes, where long-standing high blood sugar levels damage the vagus nerve that controls stomach muscle contractions. Other causes include certain medications (particularly opioids and some antidepressants), previous stomach surgery, neurological conditions, and viral infections. In many cases, no clear cause is found, and the condition is labelled as idiopathic gastroparesis.
Symptoms That Point to Gastroparesis
People with gastroparesis often experience a range of uncomfortable symptoms that significantly affect their quality of life:
Nausea and vomiting are among the most common complaints. Since food stays in the stomach too long, patients may feel sick after eating or vomit undigested food several hours after a meal.
Early satiety means feeling full after eating only a small amount. Because the stomach is not emptying properly, there is less room for new food, leading to a sensation of fullness after just a few bites.
Bloating and upper abdominal pain result from food fermenting in the stomach and gas accumulating. The distension can be quite uncomfortable.
Unintentional weight loss can occur because patients eat less to avoid symptoms, or because nutrients are not being absorbed efficiently.
Erratic blood sugar levels are a particular problem for diabetic patients. When the stomach empties unpredictably, the timing of nutrient absorption becomes unpredictable too, making blood sugar management very difficult.
These symptoms overlap with many other gastrointestinal conditions, which is why objective testing is important for an accurate diagnosis.
How the Gastric Emptying Study Works
The gastric emptying study is the standard nuclear medicine test used to measure how fast your stomach empties. It is a simple, non-invasive procedure that tracks a meal through your stomach over several hours.
The Meal
The study begins with eating a standardized meal. The most widely used protocol involves scrambled eggs (or an egg substitute) mixed with a small amount of radioactive tracer, typically technetium-99m sulfur colloid. The tracer binds to the solid food and allows the gamma camera to track its movement. You will also eat toast, drink water, and sometimes have jam with the meal. The meal is designed to be consistent across all patients so that results can be compared to established normal values.
For patients who cannot eat eggs due to allergies or dietary restrictions, alternative meals are available, though they may use slightly different reference ranges.
The Imaging
After finishing the meal, you stand or sit in front of a gamma camera. Images of your stomach are taken at specific time points: immediately after eating, and then at 1 hour, 2 hours, and 4 hours. Each imaging session takes only a few minutes. Between imaging sessions, you can sit in the waiting area. You should not eat anything else during the study.
The gamma camera detects the radioactive signal coming from the tracer in the food. As the stomach empties, the amount of radioactivity in the stomach decreases. The nuclear medicine team measures the percentage of the meal remaining in the stomach at each time point.
What Happens During the 4 Hours
You will spend most of the study sitting quietly between imaging sessions. It is a good idea to bring a book, phone, or something to pass the time. You should avoid strenuous physical activity during the study as it can affect gastric motility. Your doctor may ask you to stop certain medications before the test, particularly those that speed up or slow down stomach emptying, as they can interfere with the results.
Understanding the Results
The key measurement is the percentage of the meal retained in the stomach at the 4-hour mark. Normal gastric emptying is generally defined as less than 10 percent of the meal remaining at 4 hours. Results are typically categorized as follows:
Normal emptying: Less than 10% retained at 4 hours. This suggests the stomach is emptying at an appropriate rate.
Mild gastroparesis: 10 to 15% retained at 4 hours. Symptoms may be present but often manageable with dietary modifications and medication.
Moderate gastroparesis: 15 to 35% retained at 4 hours. Symptoms are typically more significant, and treatment usually involves a combination of dietary changes and medications that promote stomach motility (prokinetics).
Severe gastroparesis: More than 35% retained at 4 hours. Patients in this category often have significant symptoms that may require more aggressive management, including specialized nutritional support in some cases.
The 1-hour and 2-hour measurements also provide useful information about the pattern of emptying. Some patients may have normal early emptying but delayed late emptying, or vice versa, and this affects treatment decisions.
Why This Test Matters
The gastric emptying study provides objective, measurable data about stomach function. Many conditions can mimic gastroparesis symptoms, including peptic ulcers, functional dyspepsia, and even anxiety-related stomach issues. Without objective testing, there is a risk of misdiagnosis and inappropriate treatment.
The study also helps your gastroenterologist gauge the severity of the problem and track how well treatments are working over time. A repeat study after starting medication can show whether stomach emptying has improved.
Speak with Your Gastroenterologist
If you are experiencing persistent nausea, vomiting, bloating, or early fullness after meals, and your doctor suspects a motility problem, a gastric emptying study may be recommended. The test is safe, involves very low radiation, and provides information that helps guide treatment decisions. Your gastroenterologist and nuclear medicine physician will work together to interpret the results and plan the appropriate next steps for your care.