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07, Sep, 2017
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LABORATORY TESTS FOR GASTRIC ANALYSIS

Written by  on Thursday, 07 September 2017 23:53
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  1. Hollander’s test (Insulin hypoglycemia test): In the past, this test was used for confirmation of completeness of vagotomy (done for duodenal ulcer).

    Hypoglycemia is a potent stimulus for gastric acid secretion and is mediated by vagus nerve. This response is abolished by vagotomy.

    In this test, after determining BAO, insulin is administered intravenously (0.15-0.2 units/kg) and acid output is estimated every 15 minutes for 2 hours (8 post-stimulation samples). Vagotomy is considered as complete if, after insulin-induced hypoglycemia (blood glucose < 45 mg/dl), no acid output is observed within 45 minutres.

    The test gives reliable results only if blood glucose level falls below 50 mg/dl at some time following insulin injection. It is best carried out after 3-6 months of vagotomy.

    The test is no longer recommended because of the risk associated with hypoglycemia. Myocardial infarction, shock, and death have also been reported.

  2. Fractional test meal: In the past, test meals (e.g. oat meal gruel, alcohol) were administered orally to stimulate gastric secretion and determine MAO or PAO. Currently, parenteral pentagastrin is the gastric stimulant of choice.

  3. Tubeless gastric analysis: This is an indirect and rapid method for determining output of free hydrochloric acid in gastric juice. In this test, a cationexchange resin tagged to a dye (azure A) is orally administered. In the stomach, the dye is displaced from the resin by the free hydrogen ions of the hydrochloric acid. The displaced azure A is absorbed in the small intestine, enters the bloodstream, and is excreted in urine. Urinary concentration of the dye is measured photometrically or by visual comparison with known color standards. The quantity of the dye excreted is proportional to the gastric acid output. However, if kidney or liver function is impaired, false results may be obtained. The test is no longer in use.

  4. Spot check of gastric pH: According to some investigators, spot determination of pH of fasting gastric juice (obtained by nasogastric intubation) can detect the presence of hypochlorhydria (if pH>5.0 in men or >7.0 in women).

  5. Congo red test during esophagogastroduodenoscopy: This test is done to determine the completeness of vagotomy. Congo red dye is sprayed into the stomach during esophagogastroduodenoscopy; if it turns red, it indicates presence of functional parietal cells in stomach with capacity of producing acid.
 
REFERENCE RANGES
 
  • Volume of gastric juice: 20-100 ml
  • Appearance: Clear
  • pH: 1.5 to 3.5
  • Basal acid output: Up to 5 mEq/hour
  • Peak acid output: 1 to 20 mEq/hour
  • Ratio of basal acid output to peak acid output: <0.20 or < 20%
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Additional Info

  • Reference(s):
    • Burtis CA, Ashwood ER (Eds). Tietz Fundamentals of Clinical Chemistry, 4th ed. Philadelphia: WB Saunders Co, 1996.
    • Drossman DA, Shaheen NJ, Grimm IS (Eds). Handbook of Gastroenterologic Procedures (4th Ed). Philadelphia: Lippincott Williams and Wilkins, 2005.
    • Rosenfeld L. Gastric tubes, meals, acid, and analysisrise and decline. Clin Chem 1997;43:837-42.
    • Wallach J. Interpretation of Diagnostic tests (7th Ed). Philadelphia. Lippincott: Williams and Wilkins, 2000.
    • Wolfe MM, Soll AH. The physiology of gastric acid secretion. N Engl J Med 1988;319:1707-14.
Last modified on Friday, 08 September 2017 00:30
Dayyal Dg.

Clinical laboratory professional specialized to external quality assessment (proficiency testing) schemes for Laboratory medicine and clinical pathology. Author/Writer/Blogger

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