The stomach acid test is used to measure the quantity and acidity of stomach contents.

How the Test is Performed

After not eating for a period of time, fluid is all that remains in the stomach. This fluid can be removed via a tube inserted through the esophagus (food pipe).

To test the ability of cells in the stomach to secrete acid, gastrin may be injected just under the skin, into a muscle, or into a vein. The stomach contents are then removed and analyzed.

Another test involves insulin-induced hypoglycemia. Enough insulin is given under the skin or through a vein to cause the blood sugar to decrease. This causes the vagus nerve to stimulate the release of gastrin. After a short time, the stomach contents are removed and analyzed.

How to Prepare for the Test

You will be asked not to eat or drink for 4 - 6 hours before the test.

How the Test Will Feel

You may notice some discomfort or a gagging feeling as the tube is passed through your nose or mouth, and down your esophagus.

Why the Test is Performed

This test may be used for a number of reasons:

• To check if anti-ulcer medications are working
• To check if material is coming back up from the small intestine
• To evaluate the cause of malabsorption of nutrients from the intestines
• To test for the cause of ulcers

Normal Results

Normally the volume of the stomach fluid is 20 to 100 mL and the pH is acidic (1.5 to 3.5). In some situations, these numbers are converted to actual acid production in units of milliequivalents per hour.

Note: Normal value ranges may vary slightly among different laboratories. Talk to your doctor about the meaning of your specific test results.

What Abnormal Results Mean

• Decreased levels of stomach acid or gastrin can cause malabsorption.
• Increased levels of gastrin can cause increased secretion of acid and may lead to ulcers (Zollinger-Ellison syndrome).
• Ulcers may be caused by delayed emptying or increased secretion of acid.
• The presence of bile in the stomach indicates material is backing up from the small intestine ( duodenum). This may happen after a partial gastrectomy.

Risks

There is a slight risk of the tube being placed through the windpipe and into the lungs instead of through the esophagus and into the stomach. The health care provider will be sure the tube is correctly placed before continuing with the test.

If the test includes injection of insulin, there is a risk of bringing on symptoms of low blood sugar.

Alternative Names

Gastric acid secretion test