Gastric function test

Dr. Prasanth Ariyannur

Department of Biochemistry

What are the components and functions of stomach?

The gastric mucosa has different types of cell

MUCOUS SECRETING surface epithelial cellOXYNTIC OR PARIETAL CELLS

CHIEF OR PEPTIC CELL

Daily volume of gastric secretion is about 2000ml

Regulation of Acid secretion

Gastrin ,the gastro –intestinal peptide hormone (G cell) stimulate secretion of HCl.

Gastrin secretion is controlled by feed back regulation.

The vagal stimulation increases secretion of both gastric enzymes and HCl.

The most potent stimulus is histamine.

It act through specific histamine H2 receptor on the gastric mucosa

TESTS FOR GASTRIC FUNCTION

Different Measure

ment Types of Gastric

Acid Output

BASAL ACID OUTPUT (BAO) is the hourly acid output (in millimol/hour) in absence of intentional and avoidable stimulation; 0-10 millimol/hour

MAXIMAL ACID OUTPUT (MAO) is the hourly acid output (in millimol/hour) after stimulation. Sum of the acid output of the four 15 min samples. Usually 7-45 mmol/hr

PEAK ACID OUTPUT (PAO) is the hourly acid output (in millimol/hour), sum of the acid output of 2 consecutive 15 min samples of highest acid content, multiplied by 2 to get the value for one hour. Usually 12-60 mmol/hr

•Zollinger Ellison syndrome: gastrin secreting tumour . BAO is more than 15 mmol/hour . BAO/PAO is 0.6 or

higher.

•In chronic duodenal ulcer BAO,MAO,PAO are elevated.

•To check completeness of vagotomy.

•Evaluation of patient after surgery for peptic ulcer.

Indication for gastric juice analysis

Condition BAO MAO %BAO/MAO

Normal 1-5 3-40 <30

Atrophic Fundal Gastritis Achlorhydria

Atrophic Antral Gastritis 1-5 1-20 <30

Gastric Peptic Ulcer 5-10 20-40 30-40

Duodenal Peptic Ulcer 10-45 40-60 40-60

Zollinger-Ellison Syndrome >15 >60 >60

Fasting condition gastric juice is aspirated using Ryle’s tube.

Gastric juice secreted for one hour is collected as– Basal Secretion.

•Fasting stomach content aspirated (Ryle’s tube).

•Stimulation: Two pieces toast and tea or Oat meal porridge.

•Gastric Juice is collected in intervals

•Total and Free Acidity of each are measured.

•Free acid more than 50 mmol/L: Duodenal/gastric ulcer, ZES. Pyloric stenosis, Cholecystitis

Fractional test meal or FTM

•The gastric secretion is stimulated by Pentagastrin.

•A synthetic penta-peptide with terminal 4 AA same as gastrin

•Dose: 6mg/kg body weight

•Gastric secretion: collected for 1 hour in 15 minutes interval.

•Volume and pH of the samples are measured.

Pentagastrin stimulation test

•7% ethanol in 100ml

•Overnight fast, residual contents removed

•Sample every 15 min for 1 hour

•Check Total and Free acidity

Pros: Rapid, Fast emptying, easy to administer than oat meal

Cons: Non-physiological, more free acid

Alcohol Stimulation Test

•Insulin stimulates HCl acid secretion

•0.1 -0.2 units/ kg body weight of soluble insulin IV

•Hypoglycemia occur in 30 minutes

•Vagatomy : No rise in acidity over BAO is noticed during hypoglycemia

Insulin test meal (Hollander's test)

•Histamine is a potent stimulus of gastric secretion

•In this test 0.4mg/kg of histamine is given s.c, followed by collection of gastric content

Augmented Histamine Test

NO: If hypoacidity does not respond to histamine , it is true hypo acidity or histamine fast achlorhydria (due to Pernicious anemia)

YES: Hypoacidity improves to histamine it is said to be false hypoacidity

•Fasting secretion is stimulated by histamine analogue (3- amino ethyl pyrazole or “Histalog”) 10-50mg.

•Dye coupled resin (“Azure-A”) is given orally

•Based on the pH of the surrounding, resin release the dye

•The dye is excreted through urine, and the quantity excreted provides indication of presence or absence of HCl

Tubeless gastric analysis :

•Serum Gastrin: by RIA, normally the level is <10 picomol/L and never above 50 picomol/L

•OCCULT blood in gastric juice indicate gastric carcinoma,gastric or duodenal ulcer

•Presence of bile indicate regurgitation of bile

•Gastric ulcer is perpetuated by the infection of HELICOBACTER PYLORI

Other relevant clinical laboratory tests

Guaiac Slide Tests:

• Gastroccult Test: Rapid and Simple

• Determines pH and Hb concentration >300 g/dL

• For initial screening

• Hemaoccult test may vary according to acid content

Orthotoluidene Based Test (Hematest reagent tablets

and Bili-Labstix)

• Highly sensitive and specific

• Confirmatory test

Tests for Occult Blood in Gastric Juice

•Fasting content is withdrawn

•Test meal is given

•Gastric juice is withdrawn at ½ an hour interval for next 2 hours

•Free acidity measures only HCl,it is measured by titration with N/10 NaOHusing Topfer's reagent as indicator

•Total acidity include HCl and other organic acids(titration with NaOH by phenophthalein indicator)

Estimation of free acidity and total acidity

TESTS FOR MALABSORPTION

•Two orally administered doses of radio-active B12

•Measuring radioactivity in Urine specimen collected for five hours

•First test dose: B12 alone

•Second test dose: B12 with Intrinsic factor

Schilling Test

Condition 1st Stage 2nd Stage

Normal Absorption Absorption

Dietary Deficiency Absorption Absorption

Intestinal Disease Malabsorption Malabsorption

Pernicious Anemia Malabsorption Absorption

Schilling Test

•24 hr prior : Avoid eating fruits, jams, jellies and pastries (high pentose sugar foods)

•Do not eat/drink anything except plain water for prior 8 hours. (4 hours for children)

•Give 25g oral dose of D-Xylose solution drink

•Collect Blood sample after 2 hour and 5 hours (in adults). For children: 1 hour after drink.

•Collect all of urine sample in 5 hours.

•Blood level Peak in 2 hours and Completely eliminated in urine by 5 hours

D-Xylose Absorption Test

D-Xylose Absorption test (Cont’d)

Infants (5 g dose) More than 15 mg/dL (or >1 mmol/L)

Children (5 g dose) More than 20 mg/dL (or >1.3 mmol/L

Adults (5 g dose) More than 20 mg/dL in 2 hours (or > 1.3 mmol/L

Adults (25 g dose) More than 25 mg/dL in 2 hours (or > 1.6 mmol/L)

NORMAL VALUES: BLOOD

NORMAL VALUES: URINE (5 hour sample)

Children 16%-33% of the D-xylose dose is found in the sample.

Adults More than 16% of the D-xylose dose or >4 g is found in the sample.

Adults (>65 years) More than 14% of the D-xylose dose or >3.5 g is found in the sample.

D-Xylose Absorption test (Cont’d)

Malabsorption Syndromes: Auto-immune Conditions (Celiac Disease), Bacterial Infections (Whipple’s disease) or Combined (Crohn’s disease)

Inflammation of lining of gastro-intestinal epithelium

Short-bowel syndrome

Parasite infection (Giardiasis, Hookworm)

Infections causing excessive vomiting (food poisoning, gastro-enteritis)

Test is mostly replaced by antibody based tests for diagnosis

•In Duodenum, dietary fat is digested using pancreatic lipase enzyme into smaller molecules (DAG and FFA) and absorbed in Jejunum

•Normally: very less fat content

•Decreased in c/c pancreatitis, cystic fibrosis, celiac disease, SBS etc.

•Microscopy test: Random sample stained using Sudan III or Sudan IV dye

•Quantitative test: Fat extracted using organic solvents from 24 hour sample and estimated using couple saponification (alkali hydrolysis) process.

Fecal Fat Test