Gastric Emptying Scan - Procedure, Indications ,and Contraindications

Introduction:

A gastric emptying scan (GES) or gastric emptying test (GET) is a nuclear medicine study used to evaluate digestion. Nuclear medicine imaging uses a special dye called radioactive tracers or radiopharmaceuticals to detect normal and abnormal metabolic activity in the body.

Nuclear medicine was first used in the evaluation of gastric motility by Dr. Griffith and colleagues in Cardiff, Wales, in 1966, using breakfast labeled with chromium-51. The radiotracer often used in this procedure is technetium-99m sulfur colloid or DTPA (diethylenetriamine pentaacetate). For the liquid meal, indium-111 DTPA is often used.

What Are the Indications of a Gastric Emptying Scan?

The gastric emptying scan is used to detect:

1) Symptoms of gastroparesis (a condition characterized by slow movement of the muscles of the stomach that affects gastric emptying) -

• Bloating.

• Abdominal pain.

• Nausea (urge to vomit).

• Vomiting.

• Loss of appetite.

• Weight loss.

• Early satiety (feeling full after eating a small amount of food).

• Esophagitis (inflammation of the esophagus).

• Severe dehydration.

• Malnutrition from poor absorption.

2) Diabetics with poor glycemic control do not respond to treatment.

3) Esophageal reflux not responding to treatment.

4) Colonic inertia (a colonel disorder in which the colon fails to modify and move the stool from the cecum).

5) Rapid gastric emptying in cyclic vomiting syndrome.

How Do Patients Prepare for the Gastric Emptying Scan?

• Patients are asked to stop taking prokinetic agents such as Erythromycin, Metoclopramide, Domperidone, and Tegaserod for two days prior to the scan unless the scan is performed to detect the efficacy of those medications.

• Patients are asked to discontinue the medications that delay gastric emptying two days before the study. It includes opiates (Oxycodone, Codeine, and Morphine) and antispasmodic agents (Loperamide, Dicyclomine, Atropine, and Promethazine).

• Patients are instructed not to eat or drink anything four hours before the scan.

• Patients should inform the health provider about their medical conditions and their regular medications.

• Insulin-dependent diabetic patients are instructed to bring glucose monitors and medication with them. Their blood sugar should be less than 200 mg/dL, and they have to monitor their sugar level and adjust the dose of insulin according to the prescribed meal.

• It is better to schedule appointments for premenopausal women on the one to the tenth day of their menstrual cycle to avoid the effects of hormones on gastric emptying.

How Is the Gastric Emptying Scan Taken?

Meal Preparation:

• For this procedure, patients are advised to eat a light meal containing a small amount of radioactive material called radiotracers.

• The meal preparation involves solid or liquid meal preparation.

• To prepare the solid meal, egg whites are mixed with 0.5 to 1 mCi 99Tc sulfur colloid and cooking them in a non-stick pan or microwave. Adding sulfur colloid once after cooking the egg results in poor labeling of the radiotracers and lead to false measurements. The egg and radiotracer mixture is cooked until the consistency of an omelet. Then the toasted bread was spread with jam and made into a sandwich with the prepared egg. The meal should be consumed within ten minutes before the scan is taken.

• For the liquid meal, the radiotracer is mixed with 300 mL of water.

Liquid Meal:

• For the liquid meal, patients are instructed to position semi-upright (45 degrees), and the scanning is performed using a single-head gamma camera along the long axis of the stomach. The imaging should be performed immediately after the ingestion of the liquid meal, and the images are taken for one minute (one minute frame) for about 30 minutes continuously.

Solid Meal:

• Patients are asked to lie flat on the examination table after taking the solid meal. Then the radiologist will take images of the abdomen using the gamma scanner for one minute. The movement of the food labeled with radiotracer can be seen on the monitor.

• Additional images are taken within a few hours to evaluate the time taken for the food to completely empty from the stomach. Additional images are usually taken after one, two, and four hours of the initial imaging. Sometimes, optional imaging at the 30th minute helps determine rapid gastric emptying.

• Images are taken in anterior and posterior views using a dual-head gamma camera that can visualize the entire stomach, the proximal part of the small bowel, and the distal esophagus. However, sequential anterior and posterior images taken with a single-head gamma camera are also acceptable.

How Is a Gastric Emptying Scan Performed in Infants?

• Gastric emptying scan in older childer is similar to that of adults. However, in infants, the meal and the procedure have some variations.

• For infants, radiotracers are mixed with milk or formula milk. This study is known as a milk or liquid study. Parents are asked to bring milk or formula from home.

• Radiotracers used in this study are considered safe in infants. In this scan, the gastric emptying of the infant is continuously monitored for about an hour. During the scan, the child should remain still in the same place. The children can be occupied during the test by toys, music, books, or movies.

What Are the Factors Affecting the Gastric Emptying Scan?

The following factors may have a negative impact on a GES's performance and clinical validity:

• Poor glycemic control.

• Vomiting a portion of the recommended meal.

• Slow meal intake (taking longer than ten minutes).

• Incomplete meal consumption.

What Are the Alternatives to a Gastric Emptying Scan?

• Breath test.

• Ultrasound.

• Smart pill.

• Upper gastrointestinal endoscopy.

• Upper gastrointestinal series.

What Are the Contraindications of a Gastric Emptying Scan?

• Hyperglycemia - Blood glucose level of more than 250 to 275 mg/dL.

• Allergic to meals.

• Pregnancy.

• Trying to conceive.

• Breastfeeding.

Conclusion:

The gastric emptying scan is commonly used to detect the symptoms of gastroparesis and has recently been used to detect rapid gastric emptying. However, solids and liquids have different emptying rates. The liquid does not undergo trituration and shows quick distribution throughout the stomach, whereas solid shows early fundal localization. Ziessman and colleagues at John Hopkins developed a widely accepted method using 0.2 mCi of Tc-99m sulfur colloid or Indium-111 DTPA labeled with 300 mL of water to overcome the differences.