The healthy functioning of our digestive system is very important for the body. Our stomach is a reservoir of ingested food, and it is through digestion that food breaks down and becomes a source of nourishment. One of the tests which are done to get evaluate how well the digestive system is functioning is the gastric function test. The test is done to assess the acid secretory potential of the stomach by evaluating gastric juices the body produces. The tests help to diagnose chronic problems such as diarrhea, constipation, bloating, and other gastrointestinal disorders. Gastric juices are nothing but a variable mixture of water, hydrochloric acid, electrolytes, and mucus. They are clear, pale yellow, odorless fluids with acidic pH of around 1 and a gravity of approximately 1.007. The test is done through qualitative measures such as checking color, odor, and appearance and quantitative measures which implies estimating free and total acidity levels and chlorides.
Also Read: Gastroscopy: Procedure, Risks, And Results
Gastric fluids have various functions to perform. While these secretions contribute to protein digestion, gastric acidity improves the absorption of iron besides facilitating the dissociation of iron salts from the consumed food. Gastric acid also allows the formation of complexes with ascorbate and sugars which helps to enhance iron absorption by converting the gastric contents to a semi-liquid pulpy fluid (also called chyme). These juices get the food ready for further digestion which happens in the duodenum which is a part of the small intestine.
Why Does Gastric Secretion Occur?
Gastric secretion is stimulated by the act of eating also called the cephalic phase and by the arrival of food in the stomach or the gastric phase. The arrival of the food in the intestine also controls gastric secretion, termed an intestinal phase. The following factors also contribute to the process of gastric secretion:
- The gastrin hormone
- Factors such as sight, taste, and smell
- In response to vagal stimulation
- Histamine is a stimulant found in some of the body's cells
- Alcohol stimulation
Types Of Gastric Function Tests
Fractional Test Meal
The test involves the collection of stomach contents with Ryle's tube. It is a long thin rubber tube 4 mm in diameter. It has a lead piece at the tip of the tube and perforations at a short distance away from the tip. The tube is passed into the stomach, and gastric juice is collected periodically. After the samples are thus collected, they are examined for free and total acidity.
Pentagastrin Stimulation Test
Pentagastrin is an artificial peptide that can stimulate gastric secretion. In this test, the contents of the stomach are aspirated with the Ryle’s tube, collected at 15-minute intervals, and further analyzed for the next hour.
Augment Histamine Test Meal
One of the most powerful stimulants for gastric secretion, this is also aspirated at 15-minute intervals and collected for a detailed analysis. Through the test samples, the levels of acid content are measured.
Insulin Test Meal
It is mainly done to assess the results of vagotomy. Vagotomy is the process of cutting a branch of the vagus nerve to reduce stomach acid secretion. This test involves delivering electrical impulses to the vagus nerve in the brain. This is also known as Hollander's test and in this test, insulin is intravenously administered to the patient.
Tubeless Gastric Analysis
The test is helpful to ascertain the levels of gastric acidity without the use of complicated or cumbersome chemical procedures and intubation. This gastric acidity analysis is helpful to diagnose problems such as duodenal ulcers, achlorhydria, and pernicious anemia.
Test Preparation
There is no special preparation for the test besides fasting. The patient will have to fast for 12 hours overnight through the next morning till the test is completed. In most of the above types of testing, the patient is asked to swallow the bulbous end of the Ryle tube into the throat. When the first mark is at the level of the incisor teeth, the tip is at the esophagus. When the second mark is at the level of the incisor teeth, the tip has reached the stomach’s pyloric region. When the third mark is at the level of the incisor teeth, the tip is at the duodenum.
Precautions And Side Effects
Though the test is an effective way to prevent an underdiagnosis of many problems such as atrophic gastritis and other gastrointestinal issues, the test can be an unpleasant experience for most patients. It can cause complications such as nausea, vomiting, and abdominal anomalies. There can be chances of pain following the removal of the gastric tube besides a potential risk of esophageal perforation.
