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FREE LECTURE NOTES ON GASTRIC FUNCTION TESTS

Dr Vijay Marakala, MBBS. M.D. Senior Lecturer,

Department of Biochemistry, International Medical School,

MSU vkunder637@gmail.com

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

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

INTRODUCTION

Chief constituents of Gastric juice are:-

HCl

•secreted by PARIETAL CELLS

Pepsinogen

•Secreted by CHIEF CELLS

Intrinsic factor

•Required for absorption of Vitamin B12

Alkaline mucous

•Which coats the gastric walls act as lubricant

Please refer following textbook

Textbook of Medical

Biochemistry

By M. N. Chatterjea, Rana

Shinde

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

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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 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

Organic acid

Lactic acid , butyric acid present in large amount

• Hypochlorhydria, achlorhydria and Ca stomach

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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 •

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

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.

Free acid rises steadily from 15 min – ½ hr/45 min

and decreases

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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. Standard Histamine test

ii. 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

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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.

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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.

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.

•Basal secretion rate1-2.5mEq/hr

•After pentagastrin stimulus, it is 20-40mEq/hr

Normal

•15-83mEq/hr

•Mean 43

•>40 indicates duodenal ulcer

In Duodenal ulcer

•Basal secretion is > 10 mEq / hr

in Zollinger-Ellison syndrome

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• It is not reliable in patients with renal diseases, urinary retention,

malabsorption, pyloric obstruction etc.

• Used only as a screening test

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