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Overview :
Analysis
of gastric fluid may be useful in the diagnosis and monitoring of certain
gastrointestinal disorders.
The
reasons for performing gastric analysis include:
(1)
detect gastrin secreting tumors (Zollinger-Ellison syndrome)
(2)
detect recurrent peptic ulcer disease
(3)
evaluating hyperacidity
(4)
evaluating effectiveness of surgery to reduce acid output
(5)
diagnosis of achlorhydria
(6)
detect delayed gastric empyting
(7)
diagnosis of upper GI hemorrhage
Patient
Preparation:
1)
discontinuation of medications affecting gastric secretion for 24 hours prior to
testing
2)
overnight fast
3)
pass a Levin tube and confirm positioning with fluoroscopy or abdominal
X-ray
4)
stimulation with a gastric acid stimulant such as pentagastrin at dose 6 µg/kg
either SC or IM; such stimulation contraindicated in patients with GI hemorrhage
or severe peptic ulcer disease
Gastric
analysis:
1)
basal acid output, based on an overnight 12 hour collection or on a 30 minute
collection (as two 15 minute specimens);
2)
following administration of a gastric acid stimulator such as pentagastrin, with
collections every 15 minutes for 90 minutes (6 collections):
(2a)
peak acid output is the average of the two consecutive fractions with the
highest free acid; their sum is expressed in mmol/hr (after multiplying by
2)
(2b)
maximum acid output is the average
per hour output obtained from the first hour's collections (1st four
collections).
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basal acid output
(BAO) |
peak acid output
(PAO) |
ratio
BAO-to-PAO |
|
reference
population |
< 5 mEq/hour |
5-20 mEq/hour |
0.20 |
|
patients
with gastric ulcer |
< 5 mEq/hour |
5-20 mEq/hour |
0.20 |
|
patients
with duodenal ulcer |
5-15 mEq/hour |
20-60 mEq/hour |
0.4-0.6 |
|
patients
with Zollinger Ellison syndrome |
> 20 mEq/hour |
> 60 mEq/hour |
> 0.6 |
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