GASTRIC FUNCTION TESTS - A Short Power point Presentation

A short insight into GFT, gastric juice contents, functions, secretions, tests accordingly, meals types, evaluation tests

1. Gastric Function Tests -By Dr. N Revanth JR-1, Department of Physiology

2. Introduction: Gastric juice is combined secretion of three different types of cells in the gastric mucosa. Chief cells- Pepsin Parietal cells- HCl Mucus cells- Mucus pH- approx - 1 & specific gravity – 1.007

3. Composition- - 98-99% water - 1-2% solids like inorganic salts, mucin, pepsin, renin & lipase. - HCl is the important constituent of the gastric juice.

4. Functions of stomach: Reservoir of ingested foodstuffs. Mixing with gastric secretion- chyme. Secretes substances that initiate digestion.

5. Indications of gastric function tests : Diagnosis of gastric ulcer. Exclusion of diagnosis in pernicious anaemia Presumptive diagnosis of Zollinger- Ellison syndrome. Determination of completeness of surgical vagatomy .

6. Collection of sample: collection of contents of stomach – after overnight fast & after test meal Types of stomach tubes- Ewald’s tube - Rehfuss tube - Ryles tube Ryles tube marking if single ring reaches lips- Tip at cardiac end. if double ring reaches lips- Tube in stomach body

7. Classification: 1). Examination of resting contents in resting juice 2). Fraction of test meal. 3). Examination of contents after stimulation - alcohol stimulation - caffeine stimulation - histamine stimulation - augmented histamine stimulation - insulin stimulation - pentagastrin stimulation 4). Tubeless gastric analysis.

8. Test meals: Ewalds’s test meal : 2 slices of bread without butter & 250 ml tea without milk and sugar Boas test meal : tablespoon of oat meal + quart of water – boiled until it becomes pint. Alcohol : 50ml of 7% ethyl alcohol- nearly pure gastric juice can be obtained. Caffeine : 500mg caffeine sodium benzoate in 200ml warm water Histamine : subcutaneous inj 0.01mg/kg body weight. These are discarded.

9. Stimulants are used i ) Histamine : 0.04mg/kg body weight (augmented histamine test/ kay’s test) Side effects are common Reduced by giving antihistamine (H1 blocker)half hr before injection of histamine. ii) Betazol (3-aminoethyl pyrazole): synthetic analogue of histamine. Less incidence of side effects. 2mg/kg body wt dosage.

10. iii) Pengastrin : it is most favoured stimulant used nowadays. Potent & produces very few side effects. 6 mic.grm /kg body wt. subcutaneous injection

11. Examination of gastric juice : 1) Qualitative examination: - Appearance- normally clear & watery - Color - pale yellow, red- if blood is present - Odour- normally odourless - Reaction- acidic in reaction. 2) Chemical Examination: - Test for chloride- usually positive - Gunzberg’s test- HCl test, gunzberg reagent- 4grm of phlorglucinol & 2 grm of vanillin are dissolved in and madeupto 100ml in 95% ethyl alcohol.

12. - uffelmann’s test- positive test indicates Lactic acid presence. - iodine test- positive test indicates presence of starch. - Benzidine test- indicates presence of blood. - Test for pepsin- proteolytic action on casein. Test for free acidity & Total acidity: Gastric juice contains- HCl and other organic acids like lactic acid, citric acid, butyric acid Only HCl free acidity, if all- total acidity. Topfer’s indicator- upto pH- 3.6- HCl. Phenolphthalein- upto pH- 8.5- Total acidity.

13. Normal free acidity- 10-40 mEq /L. Combined acidity – 10-15 mEq /L. Achlorhydria: complete absence of HCl found in pernicious anaemia, gastric carcinoma. Histamine fast achlorhydria is diagnostic of pernicious anaemia. Hypochlorhydria: free acidity less than 10 mEq /L- Gastric ulcer, carcinomas Hyperchlorhydria: free acidity above 60mEq/L- duodenal ulcer, Zollinger- elison syndrome. These are based on HCl conc in unit volume of gastric juice- obsolete now

14. Basal output (BAO): Acid secretion during fasting, four 15 mins basal collections Before injecting pentagastrin Avg normal is 2 mEq /hour, range 1-5 mEq / hr Peak Acid Output(PAO): Post-injection 2 highest 15 mins collections within 2 hours of injection Normal range 10-40 mEq / hr

15. Maximal Acid Output(MAO): Max effective dose of pentagastrin. 4 highest 15 mins collections after the injection. Similar to PAO The BAO, PAO, MAO are nil in pernicious anaemia Decreased in gastric carcinoma. Normal in gastric ulcer. Greatly increased in Zollinger- Ellison Syndrome.

16. Determination of Total Chlorides : To differentiate between true and false achlorhydria. Whitehorn- Volhard method a simple titrimetric method is used to estimate the chloride content. Interpretation: Normal range 55- 110 mEq /l Gastric ulcer- normal or slightly subnormal Pernicious Anaemia- Absent Gastric carcinoma- low Duodenal ulcer- high Zollinger- Ellison syndrome- very high

17. In general now-a-days Gastric Function Tests are not employed as there are better visual aids being used now.