Overview of Gastric Emptying Scan
The practice of using nuclear medicine to understand how the stomach moves food through the body started in 1966. This work was done by Dr. Griffith and his team in Cardiff, Wales. They used a breakfast meal that had a radioactive substance – Chromium-51 – which gave them the ability to see how much of the meal was still left in the stomach at different times. By doing this, they were able to understand at what rate the stomach was emptying its content.
Today, we use an updated version of this test, called gastric emptying scintigraphy (GES), very often. The GES helps doctors diagnose patients who have various disorders related to the functioning of their digestive system.
There are a couple of other tests doctors use to measure gastric emptying (how quickly the stomach empties). One is the breath test. For this test, patients eat a standard meal that contains a substance called Spirulina, which has Carbon-13 in it. Once the meal moves from the stomach to the small intestine (duodenum), it gets absorbed and processed by the liver. Then, it’s breathed out by the lungs where we can measure it. This test indirectly measures stomach emptying by checking how quickly the meal moves through the body, assuming other parts like the bowel, liver, and lungs are working normally.
A different test is conducted using a wireless capsule that can measure pH levels. For this test, patients swallow a capsule along with a nutrient bar. The patient wears a belt that tracks the capsule. If the capsule moves from the stomach to the small bowel, the pH level suddenly increases, indicating it’s moved from the acidic stomach to the alkaline small bowel.
Among these tests, scintigraphy is the most popular, due to its non-invasive method and its ability to naturally measure the speed of food movement in the stomach.
Anatomy and Physiology of Gastric Emptying Scan
The stomach, located in the upper left area of your abdomen, consists of four main parts: the fundus, body, antrum, and pylorus. The fundus is the topmost part, situated towards the back left. The antrum is to the front right. The long axis of the stomach leans diagonally from the upper left of your abdomen to the middle upper part of your belly.
Each part of the stomach has a specific job. The fundus, when you eat or drink, loosens up to make space for the incoming food or liquid, a process known as ‘accommodation’. Following that, it contracts to create pressure, pushing the food towards the lower sections of the stomach. The body of the stomach is essentially a storage area for the food you eat, mixing it around, and serves as the rhythm-setter for the stomach’s movements.
The antrum plays an important role in dealing with solid food. It breaks down the food you eat into tiny pieces, around 1 to 2 mm in size, by repeatedly contracting. This process is known as ‘trituration’. Once the food is broken down to this size, the pylorus, which regulates the passage of the digested food out of the stomach, allows it to move into the small intestine, or ‘duodenum’.
Why do People Need Gastric Emptying Scan
A test called Gastric Emptying Scintigraphy (GES) is often used to check for a condition known as gastroparesis. Gastroparesis causes symptoms such as nausea, vomiting, stomach pain, and feeling full very quickly when eating. The GES test can provide helpful information if you’re having problems with acid reflux that doesn’t get better with treatment, or if you have diabetes and are struggling to control your blood sugar levels. The test can identify whether a delay in food leaving the stomach might be contributing to these issues.
Furthermore, GES can also be useful in evaluating individuals with a condition called colonic inertia, who might be considering a type of surgery called a colectomy. Colonic inertia is a type of chronic constipation, and if these patients also have slow stomach emptying, they might not respond as well to the surgery.
More recently, doctors have been using the GES test to check for a condition called rapid gastric emptying where the stomach empties too quickly. This can sometimes occur early on in patients with diabetes, and it can also be seen in cyclic vomiting syndrome. This syndrome is characterized by repeated bouts of nausea, vomiting, and tiredness.
When a Person Should Avoid Gastric Emptying Scan
There are certain situations when the recommended diet should not be followed:
If a person has allergies to the foods in the suggested meal, they should not consume it. They might have a potentially harmful reaction to some ingredients.
If a person has diabetes and their blood sugar levels are too high (above 250 to 275 mg/dL), they should not follow the recommended meal. This might cause their blood sugar to rise even further, which can be dangerous.
Equipment used for Gastric Emptying Scan
The speed at which your stomach empties after eating a meal can be affected by a number of factors. Things like the size of the meal, how easy it is to digest, the number of calories it contains, and its nutritional content all play a role. Solid foods and fatty foods tend to take longer to leave the stomach, while liquids, proteins, and carbohydrates pass through more quickly.
There used to be no standard meal for testing how quickly the stomach empties known as gastric emptying scintigraphy (GES). Different tests used different meals, including things like orange juice, cereal with milk, oatmeal, scrambled eggs, and even chicken liver. Because of these differences, it was difficult for doctors to compare the results of these tests.
To solve this problem, a group of digestive and nuclear medicine experts agreed on standard guidelines for GES in 2007. These guidelines, published in 2008, recommend a specific meal for the test. This meal includes a mixture of radioactive sulfur compound and liquid egg whites, along with two slices of white toast, some strawberry jelly, and a glass of water. Using this specific meal allows doctors to accurately compare the results of the test.
However, these guidelines only consider solid foods. Since liquids and solids leave the stomach at different rates, they might not catch some stomach disorders. Because of this, additional research has been done to include a liquid meal in the tests. Some experts have suggested a simple meal of water labeled with a radioactive sulfur compound or other tracer compounds for this part of the test.
Who is needed to perform Gastric Emptying Scan?
A specialist, known as a nuclear medicine technologist, carries out a test called the GES exam. They do this under the watchful eye of a specific type of doctor known as either a nuclear medicine physician or a nuclear radiologist. These doctors specialize in using radioactive substances in the diagnosis and treatment of diseases.
Preparing for Gastric Emptying Scan
Before having a gastric emptying scan (GES), which checks how your stomach is processing food, it’s very important to prepare correctly. This would mean making some changes to your medications and diet.
1. Certain medications, called prokinetic agents, need to be stopped for 2 days before the scan. These drugs, which include metoclopramide, erythromycin, tegaserod, and domperidone, are used to improve the movement of food through the stomach.
2. Other drugs that slow down the emptying of the stomach, like painkillers (morphine, codeine, and oxycodone) and antispasmodic agents such as atropine, dicyclomine, loperamide, and promethazine, also need to be stopped 2 days prior to the scan.
3. You’re advised to not eat or drink anything for at least 4 hours before the scan. You might be asked to stop taking anything by mouth starting from midnight before the scan, which is typically done in the morning.
If you are a diabetic and take insulin, you should bring your insulin and glucose monitor with you. Ideally, your blood sugar should be less than 200 mg/dL. You should monitor your glucose level and adjust your morning dose of insulin as needed for the meal that will be provided.
Also, for women who have a menstrual cycle, the best time to have the scans is between the 1st and 10th day of your cycle. This is because the hormones that change during the cycle can affect how your stomach empties, as some studies have suggested.
How is Gastric Emptying Scan performed
To prepare the specially marked meal, liquid egg whites are mixed with a small amount of 99Tc sulfur colloid, a substance that gives off harmless radiation that can be tracked in the body. This mixture is then cooked to resemble an omelet. Toast with jelly is prepared and combined with the cooked egg mixture to form a sandwich. The meal should be eaten within 10 minutes, and afterwards, the imaging process begins.
According to guidelines from 2008, the process of scanning and interpreting the images is consistent. This method for tracking solid foods, developed by Tougas and colleagues in 2000, involves taking images at four key points: immediately after the meal is eaten, and at 1, 2, and 4 hours later. An additional optional image can be taken 30 minutes after eating to check how quickly the stomach is emptying.
The images are then analyzed by monitoring the entire stomach area, including the lower end of the esophagus and the beginning of the small bowel. This can be achieved with a dual headed gamma camera, or with a single head camera by using both front and back images. By highlighting the images of the stomach, and comparing this with the baseline, the amount of food remaining in the stomach at each point can be calculated and compared with normal values.
Here are the published normal values:
* 30 minutes after eating: 70% or more of the meal should still be in the stomach.
* 1 hour: between 30% and 90% of the meal should be in the stomach.
* 2 hours: 60% or less of the meal should be in the stomach.
* 4 hours: 10% or less of the meal should be in the stomach.
If more than 60% of the meal is still present in the stomach 2 hours after eating, or if more than 10% of the meal is still present 4 hours after eating, this indicates slow gastric emptying. Conversely, less than 70% of the meal in the stomach 30 minutes after eating, or less than 30% of the meal in the stomach 1 hour after eating, indicates rapid gastric emptying.
In the case of a liquid meal, the radiopharmaceutical is simply mixed with water. The semi-upright patient is then imaged with a single-head gamma camera along the long axis of the stomach, every minute for 30 minutes after drinking the marked water. The remaining liquid in the stomach is then tracked by highlighting the stomach area. The speed at which the liquid is passing through the stomach is then calculated for each time point, and the time it takes to reach 50% emptying (T-1/2) is determined. According to the protocol, a T-1/2 of fewer than 22 minutes is considered normal.
Possible Complications of Gastric Emptying Scan
There are certain factors that can impact the results of a Gastric Emptying Study (GES), a test that measures how fast food leaves the stomach. These factors can make the test results less accurate and reliable. They include:
- Not finishing the whole meal provided during the test
- Taking a prolonged time to eat the meal (more than 10 minutes)
- Throwing up some of the meal
- Having uncontrolled blood sugar levels
If any of these issues happen during the test, they should be noted in the final report. The report should also mention how these issues might affect the accuracy of the test results.
What Else Should I Know About Gastric Emptying Scan?
Gastroparesis and rapid gastric emptying are conditions that affect how quickly your stomach can digest food. In these cases, food moves too slowly or too quickly through the stomach, but there’s no physical blockage causing this issue.
Previously, gastroparesis, a condition where your stomach takes too long to complete digestion, was commonly associated with stomach surgery or long-term diabetes. However, recent studies show that in most cases (32%), the cause cannot be identified and is known as ‘idiopathic’. Diabetes is the second most common cause (29%), and stomach surgery is the third (13%). It’s interesting to note that women are affected four times as much as men. Since symptoms like nausea, pain, and bloating can also occur in many other diseases, it’s hard to know exactly how many people have delayed gastric emptying. However, it’s estimated that two-thirds of the US population with diabetes, which is about 23 million people, suffer from gastroparesis. Plus, nearly half of the adults experiencing indigestion also have issues with stomach motility.
The condition of rapid gastric emptying, where your stomach empties food into your small intestine too quickly, is more common than previously thought. It’s seen in around 60% of patients with a condition called cyclic vomiting syndrome and many people with autonomic dysfunction, a disorder that affects the nerves controlling your bodily functions.
Given this high prevalence and its significant impact on public health, it’s crucial that people suffering from these conditions are accurately diagnosed. This will help guide the right treatment and manage the conditions effectively. Gastric emptying scintigraphy, a type of nuclear medicine study that measures the speed of food leaving your stomach, is key to this. Research has shown that by following the recommended guidelines of this test, we can significantly increase its accuracy in diagnosing these conditions. This will hopefully lead to further improvements in treatments and patient care.
