Synonym/Acronym
gastrin and Secretin Stimulation Test
Rationale
To evaluate gastric production to assist in diagnosis of gastric disease such as Zollinger-Ellison syndrome and gastric cancer.
Patient Preparation
There are no fluid or activity restrictions unless by medical direction. Instruct the patient to fast for 12 hr before the test. Instruct the patient to refrain from the use of chewing gum or tobacco products for at least 4 hr prior to and for the duration of the test. Instruct the patient to withhold caffeine and alcohol for 12 to 24 hr, as ordered by the health-care provider (HCP); proton pump inhibitors and other medications that interfere with GI motility should be discontinued, by medical direction, for at least 2 wk prior to the test. Protocols may vary among facilities.
Normal Findings
Method: Immunoassay.
| Age | | Gastrin Conventional Units | | Gastrin SI Units (Conventional Units × 0.481) |
|---|
| Child | | Less than 125 pg/mL | | Less than 60.1 pmol/L |
| Adult | | Less than 100 pg/mL | | Less than 48.1 pmol/L |
Values represent fasting levels.
| Stimulation Tests | | |
|---|
| Gastrin stimulation test with secretin; 0.4 mcg/kg by IV | | No response or slight increase over baseline; increase of greater than 200 pg/mL (SI units: 96 pmol/L) above baseline is considered abnormal |
Calcium may also be used as a stimulant.
(Study type: Blood collected in a red- or red/gray-top tube; related body system: Digestive system.)
Gastrin is a peptide hormone produced by the G cells of the duodenum and pyloric antrum of the stomach. Gastrin is released into the blood in response to certain stimuli, including vagal stimulation from the sight, smell, or taste of food; the presence of proteins and amino acids from partially digested food; alcohol; stomach distention; and hypercalcemia (as the main site of dietary calcium absorption is the duodenum). As blood levels of gastrin rise, gastrin is returned to the stomach to stimulate the parietal cells to secrete hydrochloric acid (gastric acid) for further digestion of food. At this point in the digestive process, gastrin also stimulates the chief cells of the stomach to secrete pepsinogen, increases antral muscle mobility, and promotes stomach contractions to stimulate gastric emptying. Gastrin also induces pancreatic secretions, gallbladder emptying, and release of intrinsic factor. Gastrin release is inhibited by the presence of acid in the stomach, somatostatin, glucagon, and calcitonin. When enough gastric acid has been produced by the stomach, gastrin levels in the blood decrease. Gastrin stimulation tests can be performed after a test meal or IV infusion of calcium or secretin.
Before the Study: Planning and Implementation
Teaching the Patient What to Expect
- Review the procedure with the patient.
- Explain that a blood sample is needed for the test.
- Discuss how this test can assist in diagnosing stomach disease.
- Inform the patient that multiple specimens will be collected if the secretin stimulation test is performed. Pretest samples will be collected at 10 min and 1 min before administration of the stimulant. Poststimulation samples will be collected at 2, 5, 10, 15, 20, and 30 min.
Potential Nursing Actions
Make sure a written and informed consent has been signed prior to the procedure and before administering any medications.
- Administer gastrin stimulators as appropriate.
After the Study: Implementation & Evaluation Potential Nursing Actions
Treatment Considerations
- Resume the usual diet and medications, as directed by the HCP.
- Instruct the patient in the use of any ordered medications and potential significant adverse effects, and encourage a literature review provided by a pharmacist.
Nutritional Considerations
- Nutritional support with calcium, iron, and vitamin B12 supplementation may be ordered, as appropriate.
- Dietary modifications may include encouraging liquids and low-residue foods, eating multiple small meals throughout the day, and avoiding foods that slow digestion, such as foods high in fat and fiber.
- Severe cases of gastroparesis may require temporary treatments that include total parenteral nutrition or use of jejunostomy tubes.
Clinical Judgement
- Consider which pain management strategy will give the best relief from gastric distress.
Follow-Up Evaluation and Desired Outcomes
- Acknowledges that depending on the results of this procedure, additional testing and HCP referral may be needed to evaluate or monitor progression of the disease process and determine the need for a change in therapy.