gastric function tests
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GASTRIC FUNCTION TESTS
Dr.Rittu ChandelM.D. Biochemistry (second yr)Grant Govt. Medical CollegeMumbai -40000824-09-13
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anatomy
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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
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Oxyntic gland
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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
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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
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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
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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
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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
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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
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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
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7. Mucus8.Organic acidsAbsence of HCl ------micro organisms thrive
and ferment food residues to produce organic acids, lactic acid and butyric acid
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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
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interpretation
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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
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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
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• 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
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•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
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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
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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
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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
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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
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•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
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biblography
•Guyton•Satyanaryan•Ranna shinde
•THANK YOU