Gastric function tests

Question 1

Gastrin

Answer 1

Peptide hormone that stimulates secretion of gastric juice (HCl) from the walls of the stomach

Question 2

What secretes gastrin

Answer 2

gastric antrum mucosa (G cells) in response to food in stomach or smell, sight, thoughts e.t.c of food

Question 3

Two ways the body regulates stomach acid secretion

Answer 3

Gastrin (negative feedback loop)
Histamines (most potent method)

Question 4

Components of gastric juice

Answer 4

Water: 97 - 99%
HCL
Organic constituents
Inorganic constituents

Question 5

What are the organic constituents of gastric juice

Answer 5

Rennin, pepsin, intrinsic factor, mucin, gastric lipase, albumin and globulin

Question 6

Inorganic constituents of gastric juice

Answer 6

Sulphate, phosphate, sodium, calcium, potassium, magnesium, chloride

Question 7

Ph of gastric juice

Answer 7

1.0 - 1.5

Question 8

Color of gastric juice

Answer 8

Colourless-grey

Question 9

Normal volume of gastric juice

Answer 9

2 - 4 litres per day

Question 10

Cells of the gastric mucosa

Answer 10

Parietal cells (secretes HCl)
Chief cells (secretes enzymes)
Surface epithelial cells (secretes mucus)

Question 11

Uses of gastric function tests

Answer 11

For creating suitable therapies for different gastro-oesophageal diseases
For drug development and delivery
For disease diagnoses

Question 12

Stimulants of gastric juice production

Answer 12

Oatmeal
Tea and toast
7% alcohol

Histamines
Pentagastrin

Question 13

Four main gastric function tests

Answer 13

Examination of resting content
Fractional gastric analysis using test meals
Examination of content after stimulation
Tubeless gastric analysis

Question 14

Procedure for examination of resting content

Answer 14

After an overnight fast, the contents of the stomach are aspirated using a size 14 Ryle’s tube and a syringe. This is analyzed for different qualities for diagnoses of diseases

Question 15

What qualities are the resting contents analyzed for

Answer 15

Volume
Consistency
Color
Mucus
Bile
Blood
Free and total acidity
Organic acids

Question 16

Resting content- volume

Answer 16

Normal is between 20 - 50 ml
More can be caused by 3 factors- Overproduction of gastric juice, Slow gastric clearance, regurgitation from duodenum

Question 17

Resting content- consistency

Answer 17

Normal is fluid-like with no food particles. May contain small amounts of mucus.

Presence of food particles are indicative of gastric carcinomas

Question 18

Resting contents - colour

Answer 18

Normal is usually colourless. May be slightly green or yellow due to regurgitation of duodenal bile.

Red or brown colour is indicative of bleeding and may be present as a result of trauma, carcinomas or ulcers.

Question 19

Resting content- mucus

Answer 19

Mucus is usually found in small amounts.
Large amounts may be indicative of gastric carcinomas, excess mucus swallowed from saliva and low HCl secretion.

Question 20

Resting content - blood

Answer 20

Blood is not normal and may be present as a result of trauma, carcinomas or ulcers.

Question 21

Resting content - bile

Answer 21

Bile may be present in small amounts due to duodenal regurgitation.
Large amounts are indicative of intestinal obstruction or ileal stasis

Question 22

Resting content - Organic acids

Answer 22

A large amount of organic acids such as lactic and butyric acid are indicative of low gastric juice secretion (Achlorhydria and hypochlorhydria) as it is not sufficient to destroy the micro-organisms present and they end up fermenting the food. This is indicative of carcinomas.

Question 23

Resting contents- Free and total acidity

Answer 23

Estimated by titration using NaOH. Methyl orange or phenolphthalein as indicators (yellow to red to signify endpoint)
Free acidity is the amount of HCl present
Total acidity is the free acidity plus the amount of organic acid present
Normal free acidity is 0 - 30mEq/L
Normal total acidity is 10 - 40 mEq/L

Question 24

Procedure for fractional gastric analysis using test meals

Answer 24

Ingestion of test meal and 5-6 ml of gastric content is collected immediately after, using a Ryle’s tube and syringe
Then more 10ml samples are collected at 15 minute intervals.
If the stomach is not cleared after 3 hours, the entire stomach content is aspirated and the volume measured.
Each sample is filtered and the filtrate is analyzed for free and total acidity. The residue is checked for blood, starch, bile and mucus

Question 25

Normal results of fractional gastric analysis

Answer 25

In normal health, free acid is found about 15-45 minutes after test meal ingestion. It then rises steadily to maximum at around 60mins to one and a half hours. At maximum, free acid is around 15 - 45 mEq/L and total acidity is usually 10 units higher. No blood, small amount of bile

Question 26

Clinical significance of results of fractional gastric analysis

Answer 26

Hyperchlorhydria: Free acidity is higher than 45mEq/L. Found in gastric, duodenal, jejunal, gastro-jejunal ulcers and gastric carcinomas

Hypochlorhydria: Low acidity. Found in gastric carcinoma and atonic dyspepsia. Free HCl absent in pernicious anemia.

Achlorhydria: No free Hcl, pepsin is present in gastric secretion

Achylia gastrica: No gastric secretion at all

Question 27

4 tests that fall under gastric stimulation test

Answer 27

Standard histamine stimulation test
Augmented histamine stimulation test
Insulin stimulation test
Pentagastrin stimulation test

Question 28

Standard histamine stimulation test procedure

Answer 28

Stomach contents are aspirated after overnight fast and analyzed
0.01 mg/kg body weight histamine is administered subcutaneously, then 10 ml of stomach contents are aspirated periodically, every 10 minutes for an hour. These samples are analyzed for free and total acidity, peptic activity and presence of blood, bile and mucus

Question 29

Standard histamine stimulation test result interpretation

Answer 29

No free HCl is indicative of achylia gastrica
More juice is secreted in duodenal ulcer

Question 30

Augmented histamine stimulation test procedure

Answer 30

Overnight fast, stomach contents are aspirated at 20 mins intervals for an hour for analysis. At half this time, 4ml anthisan is injected intramuscularly

At the end of this hour, histamine is injected (0.04mg/kg body weight) subcutaneously and the stomach contents are aspirated at 15 mins intervals for an hour for analysis

Question 31

Augmented histamine stimulation test result interpretation

Answer 31

No free acid produced in pernicious anemia
Higher acid seen in duodenal ulcer.

Question 32

Insulin stimulation test procedure

Answer 32

Blood sugar must be below 45mg% to get reliable results
Overnight fast, stomach is emptied.
15 units of soluble insulin is injected intravenously and 10ml of stomach content is collected at 15mins intervals for 2 and a half hours. The contents are analysed for free and total acidity, peptic activity, blood, bile and starch. Starch should not be present.

Question 33

Insulin stimulation test result interpretation

Answer 33

Duodenal ulcer means more acid is produced

Question 34

Pentagastrin stimulation test procedure

Answer 34

Overnight fast, stomach is cleared
Basal secretion is obtained via two 15mins interval samples
Pentagastrin is injected subcutaneously and samples are collected over 15 mins intervals for an hou

Question 35

Pentagastrin stimulation test result interpretation

Answer 35

Normal basal secretion rate is 1 - 2.5 mEq/hour
After pentagastrin injection, 20 - 40 mEq/hour

In duodenal ulcer, increase after pentagastrin is between 15 - 83 mEq/hr

Zollinger-Ellison syndrome presents with higher basal rate and no change with pentagastrin injection.

Question 36

Tubeless gastric analysis

Answer 36

DiagnexBlue is administered. This contains Azur A, an indicator. When acted on by stomach acid, this indicator is released and shows up in the urine. The released amount is then matched with a standard to get the result.
Useful as a screening test only as negative does not signify true achlorhydria.