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Transcript gastric-function
D-GASTRIC FUNCTION
TESTS
In
some diseases of Stomach & Duodenum
alterations in gastric secretion occurs,
thereby
chemical examination of gastric contents
has limited but specific value in diagnosis &
assessment of disorders of upper GIT.
Hence
to get complete data of gastric fn, the
contents of stomach should be examined
During resting period
During digestion after meals
After stimulation
Gastric juice secreted in 24 hrs is
about 1500 ml to 2000ml.
N
Chief constituents of Gastric juice
HCl………Parietal cells / oxyntic cells
- it activates the zymogen pepsinogen to pepsin by partial
proteolysis, also helps in absorption of iron and calcium.
Pepsinogen..........Chief cells
- Pepsins act on proteins and polypeptides & cleave peptide
bonds adjacent to aromatic amino acids
Gastrin: hormone secreted by G cells,
stimulates secretion of HCl.
Intrinsic Factor: Parietal cells, is a
glycoprotein required for absorption of
Vit B 12
Gastric
lipase: Chief cells. Act on
Triglycerides, convert to Fatty acids and
glycerol
Rennin
: is seen in infants but not in adults.
Alkaline
Mucus
Indications of Gastric Function Tests
To
diagnose Gastric Ulcers
To exclude the diagnosis of Pernicious
Anaemia & Peptic ulcer in Pt with GU.
For presumptive diagnosis of Zollinger
Ellison Syndrome
To determine the completeness of Surgical
Vagotomy.
CLASSIFICATION OF GFTs
Analysis
of Resting contents(Gastric
Residuum)
Fractional Test Meal Analysis
Analysis after Stimulation
# Alcohol stimulation
# Caffeine stimulation
# Histamine stimulation
CONTD……
# Augmented Histamine test
# Insulin stimulation
# Pentagastrin test
Tubeless Gastric Analysis
Other
relevant tests are estimation of Sr.Gastrin, Sr.Pepsinogen levels, Tests for Occult
blood and Tests for H.Pylori
Analysis
1)Volume
of resting contents:
: N20-50ml after a night fast
> 100-120 ml….is abnormal
Volume..
- Hypersecretion of Gastric juice
- Retention due to delayed emptying
- Regurgitation of duodenal contents.
2) Consistency : N Fluid, should not contain
food residues.
3) Colour: N Clear/ Colourless/ slight
yellow/green..
Bright red / dark red / brown…abnormal
dark brown seen in bleeding gastric ulcer,
coffee ground appearance seen in Ca
stomach.
4) Bile: Small amounts are insignificant, but
increased in Intestinal Obstruction / Ileal
Stasis.
5) Mucus: N in small amounts, increased
in gastritis , Ca Stomach.
6) Free & Total Acidity: determined by
titrating a portion of the sample with a
standard solution of NaOH.
Free
acidity measures only HCl, Topfer’s
reagent is used as indicator.
Total
acidity includes HCl and other organic
acids , Phenolphthalein is used as indicator
Normal
values
- Free Acid : 0-30 mEq / L
> 50 mEq / L indicates Hyperacidity
- Total Acid : 10-40 mEq / L
7) Organic Acids: like lactic acid & butyric
acid in large amounts indicate
achlorhydria/hypochlorhydria.
Fractional
Test Meal Analysis
Diff. meals used are
-Ewald test meal (2 pieces toast+250
ml tea)
-Oatmeal porridge
-Riegel meal..not used normally
Procedure:
After removing residual contents,
meal is given. With intervals of 15 minutes
contents of stomach are removed ,strained &
analysed.
Normally
free acid rises steadily from 15
min – ½ hr/45 min, and decreases.
Abnormal
responses are:
1) Hyperchlorhydria / Hyperacidity: when
free acid is > 50mEq / L
Seen in - Duodenal ulcer,
Gastric ulcer,
Gastric cell hyperplasia,
After Gastroenterostomy,
Contd…..
Gastric Neurosis,
Hyperirritability,
Pylorospasm ,
Pyloric Stenosis ,
Chr. Cholecystitis,
Zollinger Ellison Syndrome.
2) Hypochlorhydria / Hypoacidity:
Seen in Ca Stomach , Atonic Dyspepsia
3) Achlorhydria: No HCl is seen but pepsin is
present. Seen in Ca Stomach, Chr.Gastritis,
Partial Gastrectomy, Pernicious Anaemia,
Hyper thyroidism, Myxoedema.
Fractional Test Meal
ACHYLIA
GASTRICA : is a condition
where both enzymes and acids are absent
Seen in – Advanced Ca Stomach
-- Advanced cases of Gastritis
-- Pernicious Anaemia
-- Subacute combined
degeneration of spinal cord.
Analysis after Stimulation :
1)Alcohol
Stimulation :
-stimulant used is 7% ethyl alcohol.
- the residual contents removed after
overnight fasting, 100ml alcohol is given,
samples are taken every 15 min &
analysed for free, total acidity,peptic
activity,blood, bile,mucus.
Advantages
:
- more easy to administer
- consumed better than porridge
- gastric response is rapid
- emptying of stomach is more rapid than
porridge.
Disadvantages:
- stimulus with alcohol is not so strictly
physiological as with oatmeal.
- stimulus is more vigorous compared to
oatmeal
- rather high levels of free acidity seen.
2)
Caffeine Stimulation :
- Caffeine Sodium Benzoate,500mg dissolved in
200ml of water is given.
- Advantages are similar to that of alcohol
stimulation.
3) Histamine Stimulation Test:
- it is a powerful stimulant for secretion of HCl, acts
on oxyntic cells(specific H2receptors )
Indications
: To differentiate “ True “
Achlorhydria from “ False “ Achlorhydria
Types
of Histamine test
- Standard Histamine test
- Augmented histamine test (Kays test).
Standard
Histamine test: SC injection of Histamine 0.01mg/kg
bwt , is given.
# Results
- Absence of HCl…true achlorhydria, seen in pernicious
anemia.
- Increase in HCl…Duodenal Ulcer
Augmented Histamine test (Kays) :
larger dose, 0.04mg/kg b wt of histamine acid phosphate, SC.
Indications:
-to show inability to secrete
acid as in pernicious anemia & subacute
combined degeneration of cord.
- to assess max possible acid secretion in
diagnosis & Surg.Rx of Duodenal ulcer.
Disadv : larger dose causes severe allergic
reactions,hence another antihistaminic
given to prevent.
Procedure: After
overnight fast, residual
contents are analysed and contents are
collected every 20 min for an hr.
Halfway through this period 4ml of
mepyramine maleate (anthisan), given IM,
to block H1 receptors.
At the end of hr histamine acid
phosphate,0.04mg / kg bwt, SC given.and
contents removed every 15 min for 1 hr.
Recently,
histamine analogue,called
“Histalog”(3 beta-amino ethyl pyrazole) is
used instead of histamine
recommended dose –10-50mg
No
side effects seen hence no need to use
an antihistamine to block H1 receptors.
Insulin Stimulation test (Hollander’s
test): Hypoglycemia produced by insulin is
a potent stimulus of gastric acid secretion.
Indications: to see the effectiveness of
vagotomy in pts with duodenal ulcer.
15units of soluble insulin given IV
Disadv: Hypoglycemia
4)
Results: in pts with DU
, before operation
there is marked &
prolonged output of
acid in response to
insulin. After
successful vagotomy,
there is no response
and acid level is very
low.
5)
Pentagastrin test: Pentagastrin, synthetic
peptide, having biologically active sequence
of gastrin.It is “Butyl oxy carbonyl- beta
alanine Trp-Met-Asp-Phe CONH2”
Dose— 6 microgram/kg bwt. SC
It
is a potent stimulator, causing max
stimulation after assessing basal secretion
rate, hence it is a measure of Total Parietal
Mass.
Procedure: after removing the residual
contents , the gastric juice secreted for
next 1 hr is collected as a single sample,
which is called BASAL SECRETION.
Then
pentagastrin is given & 4 samples
are collected with 15 min intervals.
Basal Acid Output (BAO) is output in mmol
/ hr, in basal secretion.
Maximal Acid Output(MAO) is output in
mmol/hr, given by sum of the 15 min acid
output after stimulation.
Peak Acid output (PAO) is output of 2
Consecutive 15 min samples having highest acid
content and the value is multiplied by 2.
Result:
N basal
secretion rate is 1-2.5mEq/hr,
after pentagastrin stimulus..it is 20-40mEq/hr.
- in DU…. 15-83mEq/hr
- in ZE syndrome..basal secretion is > 10 mEq / hr
Tube
Less Gastric Analysis :
it avoids discomfort of naso gastric tube
Used only as a screening test.
Fasting secretion is stimulated by
histalogue , after 1 hr dye bound resin
“Diagnex Blue” with “ Azure A” is given
orally.
In
the presence of HCl resin releases
dye,which is absorbed & later excreted in
urine
The quantity of dye in urine provides
indication of presence /absence of HCl.
It is not reliable in pts with renal diseases,
urinary retention,malabsorption,pyloric
obstruction etc.
OTHER TESTS:
Serum
Gastrin : is estimated by Radio Immuno
Assay.
level
is
<
10
pico
moles/L,
N
in Zollinger Ellison Syndrome it is > 100
pmol/L.
Serum Pepsinogen :
level is 30-160units/ml
- in pernicious anaemia…very
low/absent
N
- in DU…> 200 units/ml
CONCLUSION
Gastric
Function tests are of limited
but specific value in diagnosing and
assessing some disorders of Upper
GIT.