Gastric and pancreatic function tests

Gastric function

test Out Line Chief constituents of

gastric juice Stages of gastric

secretion Inhibition of gastric

secretion Why gastric function test

are important? Tests of gastric function

with interpretation

Chief constituents of gastric juice

• Hydrochloric acid• Pepsinogen• Intrinsic factor• Gastric mucus• Blood group substances• Rennin

Stimulation of gastric secretion

• Cephalic Phase: Site, taste, smell, thought of food, insulin. Stimulation through vagus nerve.

• Gastric Phase:Food in the stomach local reflexes Vagal

activity acetylcholine gastrin from mucosa of pylorus parietal & chief cellshydrochloric acid, pepsinogen, gastric motility.

Inhibition of gastric secretion

• Entry of food into the duodenum.• Secretin, cholecystokinin-pancreozymin• Gastric Inhibitory peptide• Vasoactive Intestinal Peptide

Why gastric function test are important?

• Zolliger-Ellison Syndrome• Evaluate pernicious anemia in adults• Type of surgical procedure required for ulcer

treatment.

Stimulants for gastric secretion

• Ewald one hour meal: toast without butter, tea without milk

• Fractional test meal of Rehffus: Pint of oat meal gruel

• Histamine test: Histamine hydrochloride 0.25mg/kg subcutaneously.

• Augumented histamine test: 0.04mg/kg histamine is given subcutaneously along with antihistamine.

• Histolog.• Pentagastrin• Insulin

Titrimetric analysis of acid output

• Titrate 5ml of gastric contents with 100mmol/L NaOH either to pH 7.4 using glass electrode or to an end point with phenol red.

Acid output in mmol/h =ml of NaOH volume of specimen in ml 6ml of gastric period of collection juice titrated in minutes

Gastric acidity curves

Total acidity

Free acidity

Hypoacidity

Hyperacidity

Combined acidity

The Pentagastrin test

• Maximal stimulation of the stomach after assessment of basal secretion rate.

• Measure of total parietal cell mass.• Technique

12 hour fasting without food & drink

Pass nasogastric tube tube & site it radiologically with tip in the gastric antrum. Place the patient in recumbent position.

Empty the stomach completely with hand syringe by pressure ≤ 50mmHg

Collect two 15min specimens to give basal secretion

Pentagastrin subcutaneous injection 6µg/kg

Collect four accurately timed 15min specimens

Measure the volume, pH, acid content of 6 specimens, inspect fasting contents for blood & bile pigments

Interpretation

• It may suggest appropriate measures in active duodenal ulcer, pernicious anemia & in Zolliger- Ellison Syndrome.

• Normal basal secretion: 1 – 2.5mmol/h• Normal range of maximal secretion: 20 – 40mmol/h• Zolliger- Ellison Syndrome: basal secretion is

>10mmol/h & no further rise after giving pentagastrin.

• Achlorhydria is seen in gastric cancer, pernicious anemia. pH will be above 6.

• acute and chronic gastritis.

Insulin Stimulation test

• Insulin hypogycemia is a potent stimulus of acid secretion.

• When blood sugar is < 50.0mg/dl (2.8mmol/L) vagus is stimulated by hypoglycemia.

• This test is best limited to those patients suspected to have recurrent ulceration after vagotomy which was probably incomplete.

• Technique

12 hour fasting without food & drink

Pass nasogastric tube & site it radiologically with tip in the gastric antrum. Place the patient in recumbent position.

Empty the stomach completely with hand syringe by pressure ≤ 50mmHg

Collect four 15min specimens to give basal secretion, determine venous blood glucose immediately

Insulin intravenous injection 0.2U/kg

Collect eight accurately timed 15min specimens & determine venous blood glucose at 30 & 45 minutes

Measure the volume, pH, acid content of 12 specimens, inspect fasting contents for blood.

Interpretation

• Before operation for vagotomy there is marked & prolonged rise in acid over 100mmol/L. After successful vagotomy there is no response or only fluctuation in the baseline.

• Basal secretion 10mmol/L• Basal secretion > 20mmol/L suggest

incomplete section of vagus.

Plasma Gastrin

• Valuable in diagnosis of Zolliger- Ellison Syndrome.

• Normal plasma concentration: 50 – 150pg/ml.• Zolliger- Ellison Syndrome: 1000 –

400,000pg/ml.• Not increased in simple peptic ulcer.• Increased in pernicious anemia.

Tubeless gastric analysis

• Segal et al 1953 demonstrated direct HCl secretion without intubation by Diagnex blue.

• Principle: Orally administered quinimum resin indicator forms quinine in the stomach at pH <3 and quinine hydrochloride is generated. This is then absorbed in the small intestine, excreted in the urine. Quninine was extracted from the urine and determined florimetrically.

• Procedure

12 hour fasting

After voiding administer orally caffeine Na benzoate with water

After 1 h urine is collected as control sample

administer orally Diagnex blue with water

After 2 h urine is collected as test sample

2 samples are compared in a colour comparator with 0.3mg & 0.6mg Azur-A standards

Acidify the urine

Interpretation

Observation (Colour intensity)

Inference

<0.3mg std Achlorhydria

0.3mg to 0.6mg std Hypochlorhydria

Limitations

• It is only a screening test to assesss gastric acid secretion.

• Test is not reliable in patient suffering from pyloric obstruction, malabsorption, renal disease, urinary retention, liver disease, subtotal gastrectomy, gastroenterostomy, pyloroplasty.

• Vitamin preparation should be avoided on the day preceeding the test or medicaments given which might contain substances decolorised by ascorbic acid.

Test for Occult blood in the feces

• Definition: Tests to detect blood in feces in amounts or forms not observable on inspection are referred as occult blood test.

• Normal blood loss in the feces 2.5ml/day by radiochrome studies. Blood may be introduced from mouth, around teeth, minor abrasion in the GI tract by roughage of food, hemoglobin, myoglobin, their breakdown products, peroxidases of plant & bacterial origin.

• Benzedine test was commonly used, now prevented because of its carcinogenecity. O-toluidine is used with three different concentrations: 4%, 1.2% & 0.4% in glacial acetic acid.

• Principle:

hemoglobin & its derivatives

H2O2 H2O O2+O-Toluidine

Coloured product(Measured colorimetrically)

Test procedure

• A small portion of feces mixed in 10ml DW & boil for a minute to destroy peroxidases. Mix fecal suspension + reagent (O-toluidine & H2O2)

• Blue colour --- Positive test.• If a single concentration was used 1.2%

recommended.• If all three used 1st 4% used, positive samples tried

with 1.2%, still positive samples tried with 0.4%.

Reporting

Negative -ve with 4%

Weakly positive +ve only with 4%

Strongly positive +ve with 4%, 1.2%, 0.4%

Interpretation

• Test is mainly used in the diagnosis & treament of ulcers, cancer of stomach, gastritis, perpura, lesion in duodenum, small & large intestine.

• In case of humorrhoids blood can be seen as streeks of fresh blood on the surface of feces confirmed by misroscopic examinations.

• It is also useful practice to do the test on three successive days when the patient is on meat free diet.

• Oxyhaemoglobin released from bleeding converted to hematin & porphyrin by gastric HCl. Only hematin gives the positive test.

• In case bleeding lower down the alimentary tract, Oxyhaemoglobin released can be recognised by spectroscopic examination of supernatant fluid from a centrifuged fecal suspension.

• Does not afford any information about bleeding from mouth, nose, throught & the type of lesion present.

Out LineExocrine secretions of

PancreaseTests in Pancreatic Diseases

with interpretationDetermination of [HCO3

-]Amylase (AMS)Essay of AMS activityMacroamylasemia Isoenzymes of AMSRenal clearance of AMSLipase (LPS)Assay of LPS activity

Exocrine secretions of Pancrease

Inorganic OrganicNaHCO3(127mmol/L) α - amylaseNa+ (135-145mmol/L) LipaseK+ (3.4-5.0mmol/L) TrypsinMg+, Ca+2, Zn+(less) ChymotripsinCl- (155mmol/L) Carboxipeptidase A & B

RibonucleasesDeoxyribonucleasesCholesterolesterasesPhospholipases

Tests in Pancreatic DiseasesIntroduction

• Measurement of total volume.

• Concentration of HCO3-

• Chemical & cytological examinations performed support suspicion of malignant neoplasm, but exact localization may be unknown.

• Secretin/ CCK-PZ test: Technique

12 hour fasting without food & drink

Pass the double lumen tube & site it radiologically with tip of inner tube in the 3rd part of duodenum.

Clear bile stained juice (two 10min samples) from the deuodenal tube & juice free from bile from gastric tube were collected as basal secretion.

2-3U/kg Secretin/CCK-PZ administred intravenously over 2 min.

Pancreatic secretions are collected for 30, 60, 80 minutes.

pH, secretory rate, [HCO3-] are measured.

Determination of [HCO3-]

• To 5ml duodenal juice add 10ml of 100mmol/l HCl in a small beaker, boil to expel CO2, cool & titrate with 100mmol/l NaOH to pH 7.0 by a glass electrode or to an end point with phenolphthalein indictor.

• [HCO3-] in mmol/l =

(Vol. of HCl – Vol. of NaOH)20

Interpretation

• Normal [HCO3-] = 127mmol/L

• Secretory rate:• Men: 15mmol/h• Women: 12mmol/hRate found in pancreatic obstruction with enzyme

concentration.[HCO3

-] and enzymes associated with cystic fibrosis, chronic pancreatitis, pancreatic cysts, calcification & edema of the pancreas.

Amylase (AMS)

• Tissue source: acinar cells of pancreas & salivary glands. Lesser concentration in skeletal muscle, small intestine, fallopian tube.

• This is the smallest enzyme readily filtered through the renal glomerulus & appears in the urine.

Essay of AMS activity

• Amyloclastic method.• Saccharogenic method.• Chromogenic method.• Continuous monitering method.

Amyloclastic method

Starch + iodine =

AMS Isomaltose, maltose,glucose

blue coloured complex

blue coloured complex

Measure colour intensity colorimetrically

Saccharogenic method

Starch Isomaltose & maltoseAMS

(reducing sugars)

Reducing sugar is then measured with high alkalinity copper reagent.

The values are expressed in somogyi units. Somogyi units are an expression of the number

of mg of glucose released in 30 min under specific assay condition.

Chromogenic method

Starch with chromognic dye

AMS Starch broken down to release chromognic dye

(insoluble dye) (soluble dye)

Measure colour intensity colorimetrically

Continuous monitoring• Coupled enzyme system: change in the

absorbance of NAD+ at 340nm is measured.

Maltopentose Maltotriose + Maltose

Maltotriose + Maltose 5 glucose

5 glucose + 5 ATP 5 glucose-6-P + 5 ADP

5 glucose-6-P + 5, 6-phophogluconolactone +5 NAD+ 5 NADH

AMS

α-glucosidase

Hexokinase

G6PDH

Interpretation• Reference ranges of AMS:

• Serum: 25 – 130U/L.• Urine: 1 – 15U/L.• Approximate conversion factor between somogyi units &

international units is 1.85

• In acute pancreatitis AMS begin to rise 2 – 12 h after the onset of attack, peak at 24h & return to normal within 3 – 5 days. Values generally varies between 250 – 1000 somogyi units/dl.

• In salivary gland lesion, mumps, parotitis, perforated peptic ulcer, intestinal obstruction, cholecystitis, ruptured ectopic pregnancy, mesenteric infarction, acute appendicitis, renal insufficiency, diabetic ketoacedosis.

• Serum AMS other than acute pancreatitis are usually less than 500 somogyi units/dl.

Macroamylasemia (asymptomatic)

• Diagnostic significance: Differentiate macroamylasemia from hyperamylasemia.

ImmunoglobulinAMS + Big complex(Can not be filtered through glomerular membrane)

Isoenzymes of AMS

• P-type: pancreatic• S- type: salivary, fallopian tube, lung• Isoenzymes of salivary origin migrate most quickly

(S1, S2, S3), where as pancreatic origin move slower (P1, P2, P3).

• AMS migrate in the regions corresponding to β to α-globulin regions of the protein.

• P-type activity, specifically P3 in acute pancreatitis

Renal clearance of AMS• Useful in detecting minor or intermittent in serum

concentration.

• Normal Values: < 3.1%• Acute pancreatitis: 8% - 9%• Also in burns, sepsis, diabetic ketoacedosis.

% AMS clearanceCreatinine clearance= 100

UA SCSA UC

× ×

Lipase (LPS)Assay by titrimetric method:

• Tissue source: primarily in pancreas, little in stomach & small intestine.

• Classical Cherry-Crandall method used an olive oil substrate & measured the liberated FA by tritration after 24h incubation. Trioline is one of the substance now used as a more pure form of TAG.

triglyceride+ 2H2OLPS

pH 8.6-92-monoglyceride+2-fatty acid

Turbidimetric method

Fats in solution

(cloudy emulsion)

LPS Hydrolysed fat in solution

(Fat particles disperse)

Rate of clearing of the fat in the solution is measured.

Interpretation

• Reference range: 0 – 1.0U/ml• This is exclusive for the diagnosis of acute

pancreatitis.• Both AMS & LPS levels rise quickly, but LPS

elevation persist for 5 days, whereas AMS only for 2 – 3 days.

• Elevated also in penetrating duodenal ulcer, intestinal obstruction, acute cholecystitis.

• In contrast to AMS levels, LPS levels are normal in conditions of salivary gland involvement.

• Of the three LPS isoenzymes, L2 is thought to be most clinically specific & sensitive.