Gastric function tests

1. GASTRIC FUNCTION TESTS Dr.Rittu Chandel M.D. Biochemistry (second yr) Grant Govt. Medical College Mumbai -400008 24-09-13

2. anatomy

3. functions Reservoir of ingested foodstuffs Mixing of food with gastric secretion until it forms a semifluid mixture called chyme Secretes substances which are responsible for initiation of digestion

4. Oxyntic gland

5. Secretion of gastric HCl Parietal cells ---------- HCl pH in gastric lumen ------- 0.8 (very low as compared to blood pH ---- 7.4) Hence protons are transported against concentration gradient by active process

6. Indications of gastric function tests Diagnosis of gastric ulcer Exclusion of diagnosis in pernicious anemia Presumptive diagnosis of Z ollinger – Ellison syndrome Determination of completeness of surgical vagotomy

7. classification 1.Examination of resting contents in resting juice 2.Fractional test meal 3.Examination of contents after stimulation alcohol stimulation caffeine stimulation histamine stimulation augmented histamine test insulin stimulation test pentagastrin test 4.Tubeless gastric analysis

8. Collection of sample Collection of contents of stomach After overnight fast After test meal Types of stomach tubes Rehfuss tube Ryles tube Markings on tube Single ring reaches lips Tip reaches cardiac end Double ring reaches lips Tube in body of stomach

9. Examination of resting contents 1.Volume Normal ----20 – 50 ml Abnormal -----greater than 100 – 120 ml 2.Consistency Normal -----fluid Abnormal ----food residues Hypersecretion of gastric juice Retention of gastric contents due to delayed emptying Due to regurgitation of duodenal contents

10. 3.Colour Normal -----clear or colourless Abnormal ------bright red/dark red/brown colour 4.Bile 5.Blood 6.Free and total acidity Determined by titrating a portion of the filtered specimen with standard solution of NaOH

11. Two indicators are used in succesion inferences indicators Measures pH Methyl orange 2.9 to 4.4 (red ------yellow) phenolphthalein 8.3 to 10 (yellow ----- red ) Free acidity First titration 0 – 30 mEq /L Total acidity Complete titration 10 – 40 mEq /L Combined acid Difference between two titrations

12. 7. Mucus 8.Organic acids Absence of HCl ------micro organisms thrive and ferment food residues to produce organic acids, lactic acid and butyric acid

13. Fractional gastri c analysis/fractional test meal

14. interpretation

15. Abnormal responses Hyperacidity/ hyperchlorhydria Max free acidity exceeds 45 mEq /L Duodenal ulcer Gastric ulcer Gastric carcinoma hyperirritability hypoacidity Free acid below the normal range Pernicious anemia achlorhydria No secretion of HCl but enzyme pepsin is present Carcinoma stomach Partial gastrectomy Pernicious anemia Hyperthyroidism myxedema Achylia gastrica – both enzymes and acids are absent indicating complete absence of gastric secretions Advanced gastric cancer Typically seen in pernicious anemia and subacute combined degeneration of spinal cord

16. Stimulation tests – alcohol stimulation test Alcohol stimulation test

17. Caffeine stimulation Stimulus ----caffeine sodium benzoate (500 mg in 200 ml water) given orally Histamine stimulation test Powerful stimulant for HCl in normal stomach Acts on receptors of oxyntic cells, increasing cAMP , which causes secretion of increased volume of high acidic gastric juice with low pepsin content Best to differentiate between true achlorhydria from false achlohydria

18. Augmented histamine test Normal persons Upto 10 mEq /hr acid is present in pre histamine specimen , with 10 -25 mEq in post histamine specimens Pernicious anemia No free HCl secreted Duodenal ulcer > 100 meq Now histalog ( 3 β – aminoethylpyrazole ) is used in place of histamine

19. Insulin stimulation test ( hollander’s test) Potent stimulus for gastric acid secretion – hypoglycemia Indication To check the effectiveness of vagotomy in patients with duodenal ulcer Stimulus – 15 unit of soluble insulin iv

20. Pentagastrin test Synthetic peptide N terminal ---- butyloxycarbonyl – β alanine C terminal ---- Trp – Met – Asp – Phe Measure of total parietal mass Stimulus – 6 micg /kg body wt given sc

21. condition Basal secretion Maximal scretion normal 1 – 2.5 mEq /hr 20 – 40 mEq /hr Duodenal ulcer Gastric cancer Pernicious anemia Above 40 mEq /hr True achlorhydria True achlorhydria

22. Tubeless gastric analysis Quininium resin given orally in stomach quinine ions liberted at pH < 3 Quinine liberated forms quinine HCl which is excreted in urine Quinine is extracted and determined fluorimetrically Thus it gives indirect measure for acid secretion

23. Only a screening test Positive result – acid being secreted Negative result - unreliable indicator of true achlorhydria Test not reliable in patients suffering from renal diseases, urinary retention, malabsorption

24. biblography Guyton Satyanaryan Ranna shinde THANK YOU