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 emptying

(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). 




basal acid output (BAO)

peak acid output (PAO)

ratio BAO-to-PAO

reference population

< 5 mEq/hour

5-20 mEq/hour


patients with gastric ulcer

< 5 mEq/hour

5-20 mEq/hour


patients with duodenal ulcer

5-15 mEq/hour

20-60 mEq/hour


patients with Zollinger Ellison syndrome

> 20 mEq/hour

> 60 mEq/hour

> 0.6


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