GASTRIC FUNCTION TESTS

Dr.Rittu ChandelM.D. Biochemistry (second yr)Grant Govt. Medical CollegeMumbai -40000824-09-13

anatomy

functions

1. Reservoir of ingested foodstuffs2. Mixing of food with gastric secretion

until it forms a semifluid mixture called chyme

3. Secretes substances which are responsible for initiation of digestion

Oxyntic gland

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

Indications of gastric function tests1. Diagnosis of gastric ulcer2. Exclusion of diagnosis in pernicious

anemia3. Presumptive diagnosis of Zollinger –

Ellison syndrome4. Determination of completeness of

surgical vagotomy

classification1.Examination of resting contents in resting juice2.Fractional test meal3.Examination of contents after stimulation alcohol stimulation caffeine stimulation histamine stimulation augmented histamine test insulin stimulation test pentagastrin test4.Tubeless gastric analysis

Collection of sample

•Collection of contents of stomachAfter overnight fast After test meal• Types of stomach tubesRehfuss tubeRyles tube• Markings on tube

Single ring reaches lips

Tip reaches cardiac end

Double ring reaches lips Tube in body of stomach

Examination of resting contents1.Volume Normal ----20 – 50 mlAbnormal -----greater than 100 – 120 ml

2.ConsistencyNormal -----fluidAbnormal ----food residues

Hypersecretion of gastric juice

Retention of gastric contents due to delayed emptying

Due to regurgitation of duodenal contents

3.ColourNormal -----clear or colourlessAbnormal ------bright red/dark red/brown

colour4.Bile5.Blood6.Free and total acidityDetermined by titrating a portion of the

filtered specimen with standard solution of NaOH

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

7. Mucus8.Organic acidsAbsence of HCl ------micro organisms thrive

and ferment food residues to produce organic acids, lactic acid and butyric acid

Fractional gastric analysis/fractional test meal

Introduction of ryles tube in stomach of fasting patientRemoval of residual gastric contents and its analysis

Ingestion of test meal

Analysis of samples

interpretation

Abnormal responsesHyperacidity/hyperchlorhydria

Max free acidity exceeds 45 mEq/L

Duodenal ulcerGastric ulcerGastric carcinomahyperirritability

hypoacidity Free acid below the normal range

Pernicious anemia

achlorhydria No secretion of HCl but enzyme pepsin is present

Carcinoma stomachPartial gastrectomyPernicious anemiaHyperthyroidismmyxedema

Achylia gastrica – both enzymes and acids are absent indicating complete absence of gastric secretionsAdvanced gastric cancerTypically seen in pernicious anemia and subacute combined degeneration of spinal cord

Stimulation tests – alcohol stimulation test•Alcohol stimulation test

Overnight fast, ryles tube passed – resting contents removed for analysis

100 ml of 7% ethyl alcohol is administered

Samples removed after every 15 mins and analysed for free and total acidity, presence of bile, blood and mucus

• Caffeine stimulationStimulus ----caffeine sodium benzoate (500 mg

in 200 ml water) given orally• Histamine stimulation testPowerful stimulant for HCl in normal stomachActs 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

•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 ( 3β –aminoethylpyrazole) is used in place of histamine

Insulin stimulation test (hollander’s test)•Potent stimulus for gastric acid secretion

– hypoglycemia•IndicationTo check the effectiveness of vagotomy in

patients with duodenal ulcerStimulus – 15 unit of soluble insulin iv

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

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

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

•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

biblography

•Guyton•Satyanaryan•Ranna shinde

•THANK YOU