Gastric function test

Gastric function test,it analysis and clinical significance

1. GASTRIC FUNCTION TEST Dr. Achla jain Guest lecturer SOS in Life sciences Pt. Ravishankar shukla University, Raipur

2. GFT - Introduction The chief constituents of gastric juice are: • HCl secreted by the parietal cells, • Pepsinogen: Secreted by zymogen cells or “chief” cells. • Rennin: Not found in adult gastric juice. Only found in infants/babies. • Intrinsic factor: Required for absorption of vitamin B12, and other cells produce an alkaline mucus.

3. The gastric mucosa has different types of cell mucous secreting surface epithelial cell oxyntic or parietal cells chief or peptic cell. Daily volume of gastric secretion is about 2000ml

4. GFT - INDICATIONS

5. GFT – CLASSIFICATIONS

6. CLASSIFICATION Tests commonly employed for assessing gastric function are: A. Examination of resting contents in resting juice (gastric residuum). B. Fractional gastric analysis using a test ‘meal’. C. Examination of the contents after stimulation: “Alcohol” stimulation. Caffeine stimulation. Histamine stimulation. Augmented histamine test. Insulin stimulation. Pentagastrin test. D. Tubless gastric analysis.

7. Collection of Contents of Stomach 1. The stomach contents are collected after introducing a stomach tube by nasogastric route into the stomach and removing the contents by aspiration. The resting gastric contents are completely removed for examination. 2. Gastric contents are removed after a “test meal” to see the response of stomach. In this, small samples 5 to 6 ml of the gastric contents are removed after every 15 minutes and the samples are collected in small sterile clean penicillin bottles.

8. Analysis of resting contents NORMAL ABNORMAL CAUSES Volume 20-50mL >100-120mL Hypersecretion of Gastric juice Retention due to delayed emptying Regurgitation of duodenal contents Consistency - Fluid Food residues Carcinoma of stomach Colour – clear- colourless or slightly yellowish or green Dark red or brown Due to blood Bleeding Gastric ulcer Carcinoma of stomach Bile – occasionally Increased amount Intestinal Obstruction and ileal stasis. Mucus - small amount Increased amount Gastritis and carcinoma of stomach

9. Analysis of resting contents NORMAL ABNORMAL CAUSES Organic acid Lactic acid , butyric acid present in large amount Hypochlorhydria, achlorhydria and Ca stomach Free acidity-measures only HCl. 0-30mEq/L >50mEq/L Hyperacidity Total acidity – includes HCl and other organic acids. Normal 10-40mEq/L Pepsin Decreased levels Increased levels Atrophic gastritis, Ca stomach Zollinger-Ellison syndrome

10. Fasting condition gastric juice is aspirated using Ryle’s tube. Gastric juice secreted for one hour is collected as– Basal Secretion

11. Fractional gastric analysis: using test meals Fractional Gastric analysis: Also called Fractional Test Meal (FTM) It consists of the following steps: 1.Introduction of Ryle’s tube in stomach of a fasting patient (overnight). 2. Removal of residual gastric contents and its analysis. 3. Ingestion of “test meal” 4. Removal of 5 to 6 ml of gastric contents after meal by aspiration using a syringe and analysis of the samples.

12. Fractional test meal or FTM Fasting stomach content aspirated (Ryle’s tube). Stimulation : Two pieces toast and tea or Oat meal porridge . Gastric Juice is collected in intervals. Total and Free Acidity of each are measured. Free acid more than 50 mmol /L: Duodenal/gastric ulcer, ZES. Pyloric stenosis , Cholecystitis

13. Collection of samples: At intervals of exactly 15 minutes, about 10 ml of gastric contents are removed by means of syringe attached to the tube. Analysis of the samples: Each sample is strained through a fine mesh cheese cloth. The residue on the cloth is examined for mucus , bile , blood and starch. The strained samples are analyzed for free and total acidity.

14. Results and Interpretation of the Tests A. Normal Response In normal health: After taking the meal, free acid is again found after 15 to 45 minutes. The free acid then rises steadily to reach a maximum at about 15 mts to ½ hour, after which the concentration of free acid begins to decrease. Free acid ranges from 15 to 45 mEq/ litre at the maximum with total acid at about 10 units higher. About 80 per cent of normal people fall within these limits. Blood should not be present and there should not be any appreciable amount of bile.

15. B. Abnormal Responses Three types of abnormal responses: 1. Hyperacidity (hyperchlorhydria): In which free acid reaches a higher concentration than in normal persons. 2. Hypoacidity (hypochlorhydria): In which though free acid is present, it is present in a concentration below the normal range. 3. Achlorhydria: In which there is no secretion of free acid at all.

16. 2.FRACTIONAL TEST MEAL ANALYSIS

17. STIMULATION TESTS Alcohol Stimulation 7% ethanol in 100ml Overnight fast, residual contents removed Sample every 15 min for 1 hour Check Total and Free acidity Pros: Rapid, Fast emptying, easy to administer than oat meal Cons: Non-physiological, more free acid.

18. B. Caffeine Stimulation Caffeine can be used as a stimulus instead of alcohol. Procedure 1. Ryle’s tube is introduced after an overnight’s fast and the resting gastric contents are removed and analyzed. 2. Caffeine sodium benzoate, 500 mg dissolved in 200 ml of water is given to the patient orally. 3. Samples of stomach contents are removed every 15 minutes and analyzed for free and total acidity, peptic activity, blood, bile and mucus. Advantages of caffeine stimulation is similar to alcohol stimulation.

19. C. Histamine Stimulation Test Histamine is a powerful stimulant for the secretion of HCl in the normal stomach. It acts on receptors on the oxyntic cells, increasing the cyclic AMP level, which causes secretion of an increased volume of highly acidic gastric juice with low pepsin content.

20. Procedure 1. After an overnight’s fast, Ryle’s tube is passed into the stomach and stomach contents are removed for analysis. 2. Patient is given a subcutaneous injection of histamine, 0.01 mg/kg body wt. 3. After the injection, 10 ml of stomach contents are removed every 10 minutes for one hour. The samples are analyzed for free and total acidity, peptic activity, and for presence of blood, bile and mucus. Types of histamine test: I. Standard histamine test and II. Augmented histamine test.

21. Clinical significance • Absence of free HCl in the secretions after histamine indicate “achylia gastrica” (“true” achlorhydria). • In duodenal ulcer: More juice may be secreted and a higher concentration of acid may be found in the specimen obtained after histamine administration than in normal cases. I. Standard Histamine Test

22. II. Augmented Histamine Test (Kay) Histamine is a potent stimulus of gastric secretion . In this test 0.4mg/kg of histamine is given s.c , followed by collection of gastric content Disadvantage: Larger doses of histamine used in this test causes untoward severe reactions and hence an antihistaminic will have to be given side by side to prevent any such reactions.

23. Clinical significance • In normal persons: Up to 10 mEq/hour acid is present in the prehistamine specimen, with 10 to 25 mEq in the combined post-histamine ones. • In pernicious anemia: No free HCl is secreted after augmented histamine stimulation (achylia gastrica), but in other forms of achlorhydria (false achlorhydria), some amount of free HCl is secreted after histamine stimulation. • In duodenal ulcers: Higher values are obtained sometimes reaching even exceeding 100 mEq.

24. D. Insulin Stimulation Test (Hollander’s Test) Insulin stimulates HCl acid secretion 0.1 -0.2 units/ kg body weight of soluble insulin IV Hypoglycemia occur in 30 minutes Vagatomy: No rise in acidity over BAO (basal acid output) is noticed during hypoglycemia

25. Procedure 1. After an overnight fast, pass a Ryle’s tube and empty the stomach. 2. Then give 15 units of soluble Insulin intravenously(IV). 3. After injecting the insulin, withdraw approximately 10 ml samples of gastric contents every 15 minutes for 2½ hours. 4. Samples to be analyzed for free and total acidity, peptic activity and presence of blood, bile and starch. No starch should be present.

26. Clinical significance • In patients suffering from duodenal ulcer, before operation, there is a marked and prolonged output of acid in response to insulin. The concentration of free acid may rise well over 100 mEq/litre. • After a successful vagotomy there is no response to Insulin and the gastric acidity remains at a low level of 15 to 20 mEq/L, before and after insulin injection .

27. E. Pentagastrin stimulation test The gastric secretion is stimulated by Pentagastrin. A synthetic penta-peptide with terminal 4 AA same as gastrin Dose: 6mg/kg body weight Gastric secretion: collected for 1 hour in 15 minutes interval. Volume and pH of the samples are measured.

28. Clinical significance • Normal basal secretion rate is 1 to 2.5 mEq/hour. After pentagastrin stimulus, maximal secretion in normal persons roughly varies from 20 to 40 mEq/hr. • In duodenal ulcer: The range was 15 to 83 mEq/hour with a mean of 43. Values above 40 mEq/hour has been kept which is suggestive of duodenal ulcer. • Zollinger-Ellison syndrome: It is characterised by a high basal secretion usually above 10 mEq/hr; if, it is maximal then, there will be no further rise after giving pentagastrin, otherwise only a small to moderate increase is seen. • In gastric ulcer: The test is of little value.

29. Serum pepsinogen Pepsinogen determination has been used to investigate the gastric secretion of this enzyme . A convenient method using the digestion of dried serum has been used. Interpretations • Normal value: Ranges from 30 to 160 units/ml. • Pernicious anaemia: Serum pepsinogen is absent or very low. • Duodenal ulcer : An increase is often found upto and above twice the upper limit of normal. If the serum pepsinogen is less than < 80 units/ml; it is considered that an ulcer is not present.

30. Tubeless gastric analysis : Fasting secretion is stimulated by histamine analogue ( 3- β amino ethyl pyrazole or “Histalog”) 10-50mg. Dye coupled resin (“Azure-A”) is given orally Based on the pH of the surrounding, resin release the dye The dye is excreted through urine, and the quantity excreted provides indication of presence or absence of HCl