Published on March 8, 2014
FREE LECTURE NOTES ON GASTRIC FUNCTION TESTS Dr Vijay Marakala, MBBS. M.D. Senior Lecturer, Department of Biochemistry, International Medical School, MSU firstname.lastname@example.org Introduction Indications Classification Analysis of Resting contents Bile Blood Mucous Free acidity Total acidity Fractional Test Meal Analysis Analysis after Stimulation Alcohol stimulation Caffeine stimulation Histamine stimulation Augmented histamine stimulation Insulin stimulation Pentagastrin stimulation Tubeless Gastric Analysis Please refer following textbook Textbook of Medical Biochemistry By M. N. Chatterjea, Rana Shinde INTRODUCTION Chemical examination of gastric contents has limited but specific value in diagnosis & assessment of disorders of upper GIT. Normal fasting gastric juice per day is about 1L. Stomach of a person taking a normal diet secretes 2L 3L of gastric juice per day. Contents of stomach should be examined During resting period During digestion after meals After stimulation Chief constituents of Gastric juice are:HCl •secreted by PARIETAL CELLS Pepsinogen Intrinsic factor •Secreted by CHIEF CELLS •Required for absorption of Vitamin B12 Alkaline mucous •Which coats the gastric walls act as lubricant INDICATIONS To diagnose Gastric Ulcers To exclude the diagnosis of Pernicious anaemia & Peptic ulcer For presumptive diagnosis of Zollinger Ellison Syndrome To determine the completeness of Surgical Vagotomy. Gastric contents are collected using Ryle’s tube 1
CLASSIFICATION 1. Examination of Resting contents(Gastric Residuum) 2. Fractional Test Meal Analysis 3. Analysis after Stimulation a. Alcohol stimulation b. Caffeine stimulation c. Histamine stimulation d. Augmented Histamine test e. Insulin stimulation f. Pentagastrin test 4. Tubeless Gastric Analysis EXAMINATION OF RESTING CONTENTS: Contents of the stomach collected after overnight fasting. Some of the important physical and chemical characteristics are: NORMAL ABNORMAL Volume 20-50mL >100-120mL Consistency - Fluid Food residues Colour – clearDark red or brown* colourless or slightly Due to blood yellowish or green Bile – occasionally Increased amount Mucus - small amount Organic acid Increased amount Lactic acid , butyric acid present in large amount CAUSES • Hypersecretion of Gastric juice • Retention due to delayed emptying • Regurgitation of duodenal contents • Carcinoma of stomach • Bleeding Gastric ulcer • Carcinoma of stomach • Intestinal Obstruction and ileal stasis. • Gastritis and carcinoma of stomach • Hypochlorhydria, achlorhydria and Ca stomach 2
Free aciditymeasures only HCl. 0-30mEq/L >50mEq/L • Hyperacidity • Total acidity – includes HCl and other organic acids. Normal 10-40mEq/L • Pepsin Decreased levels • Atrophic gastritis, Ca stomach Increased levels • Zollinger-Ellison syndrome • FRACTIONAL TEST MEAL ANALYSIS: Introduction of Ryle’s tube in stomach of fasting patient and removal of residual gastric contents and its analysis. Then ingestion of ‘TEST MEAL’ and removal of gastric contents after meal. There are different types of test meals have been used Ewald test meal (2 pieces toast+250 ml tea) Oatmeal porridge NORMAL RESPONSE Free acid rises steadily from 15 min – ½ hr/45 min and decreases ABNORMAL RESPONSE Hyperchlorhydria: When free acid is > 50mEq / L. Seen in duodenal ulcer, gastric ulcer, gastric carcinoma. Hypochlorhydria: Seen in carcinoma of stomach, atonic dyspepsia Achlorhydria: No HCl but pepsin is present. Seen in Ca stomach, chronic gastritis. 3
Achylia gastrica: Both HCl and pepsin are absent. Seen in later stage of Ca stomach chronic gastritis and pernicious anaemia. ANALYSIS AFTER STIMULATION: ALCOHOL STIMULATION TEST: The residual contents removed after overnight fasting 100ml of 7% ethyl alcohol is given Samples are taken every 15 min Analysed for free, total acidity, pepsin, blood, bile and mucus. CAFFEINE STIMULATION TEST: Stimulus is caffeine sodium benzoate -500 mg in 200 ml water given orally. Samples are taken every 15 min then analysed for free, total acidity, pepsin, blood, bile and mucus. HISTAMINE STIMULATION TEST: Histamine is the powerful stimulant for HCl in normal stomach Acts on receptors of oxyntic cells Done to differentiate between “true” achlorhydria from “false” achlorhydria There are two types of Histamine stimulation test: i. ii. Standard Histamine test Augmented Histamine test Standard Histamine test: Histamine is given subcutaneously 0.01mg/kg body weight Absence of HC indicates “Achylia gastrica (true achlorhydria) Increase in HCl indicates Duodenal Ulcer 4
Augmented Histamine test (Kay’s test): It is more powerful test than standard Histamine test as it provides more reliable proof of an inability to secrete acid. Procedure: After overnight fast, residual contents are analysed and contents are collected every 20 min for an hr. Halfway through this period 4ml of mepyramine maleate (anthisan), given IM, to block H1 receptors. At the end of hr histamine acid phosphate, 0.04mg / kg bwt, SC given and contents removed every 15 min for 1 hr. Normal response: Upto 10 mEq/hr acid is present in pre histamine specimens with 10 -25 mEq/hr in post histamine specimens. In pernicious anaemia: No free HCl secreted In duodenal ulcer: Higher values are obtained sometimes even > 100 mEq/hr INSULIN STIMULATION TEST (HOLLANDER’S TEST) Hypoglycemia produced by administration of Insulin is potent stimulus for gastric acid secretion. Indication: To check the effectiveness of vagotomy in patients with duodenal ulcer Stimulus – 15 unit of soluble insulin iv Results I. Before operation II. After successful vagotomy, there is no response and acid level is very low. 5
PENTAGASTRIN TEST It is a potent stimulator, causing max stimulation after assessing basal secretion rate; hence it is a measure of Total Parietal Mass. • Procedure: after removing the residual contents, the gastric juice secreted for next 1 hr is collected as a single sample, which is called BASAL SECRETION. Then injection of Pentagastrin is given at a dose of 6 microgram/kg bwt, subcutaneously. Collect 4 specimens at 15min intervals for next 1 hour and analysed. • Basal secretion rate1-2.5mEq/hr • After pentagastrin stimulus, it is 2040mEq/hr • 15-83mEq/hr • Mean 43 • >40 indicates duodenal ulcer Normal In Duodenal ulcer • Basal secretion is > 10 mEq / hr in ZollingerEllison syndrome TUBLESS GASTRIC ANALYSIS Swallowing a Ryle’s tube is an unpleasant procedure so tubeless gastric analysis avoids discomfort of naso-gastric tube. • Fasting secretion is stimulated by histalogue, after 1 hr dye bound resin “Diagnex Blue” with “Azure A” is given orally. • In the presence of HCl resin releases dye, which is absorbed & later excreted in urine • The quantity of dye in urine provides indication of presence /absence of HCl. 6
• It is not reliable in patients with renal diseases, urinary retention, malabsorption, pyloric obstruction etc. • Used only as a screening test ****************************************** 7
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