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Updated: 12/20/06 02:10 PM |
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E. Measurement of Gastric Acid Secretion
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1. Basal Acid Output (BAO)
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After an overnight fast a tube is positioned in the dependent portion of the stomach under fluoroscopic control. The stomach is then emptied, and four continuous fifteen-minute aspirations are obtained. The basal acid output is the acid secreted without any known stimulation. BAO varies between individuals and there are significant circadian changes
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2. Maximal Acid Output (MAO)
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Induced by SQ pentagastrin.
H+ secretory rates are very variable: 1-2 meq/h basally 20-30 meq/h post-pentagastrin Zollinger-Ellison syndrome: 10-15 meq/h basally plus ↑ serum gastrin. |
After the basal secretory rate has been measured, pentagastrin is given subcutaneously. Gastric juice is continuously collected for the subsequent 1 1/2 to 2 hours.
Both basal and maximal stimulated tests have a wide range in normal people. Normally a man secretes 1-2 meq of H+ per hour basally and 20-30 meq per hour after pentagastrin (MAO is higher in men than in women and higher in smokers than nonsmokers). Although the mean stimulated secretory rate of duodenal ulcer patients is higher than that of controls, there is an area of overlap which includes about half of normal individuals and half of the patients with duodenal ulcer. Male patients with gastrin-secreting tumors (Zollinger-Ellison syndrome) usually have basal secretory rates over 15 meq per hour, and females over 10 meq per hour; serum gastrin (by immunoassay) is abnormally high in these patients. Patients with pernicious anemia, whose fundal glands have atrophied, do not secrete acid even after pentagastrin. |
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Next Section (F & G): The Role of the Stomach in Satiety and Weight Loss & Gastric Digestion » |
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