Functional and provocative tests for gastroduodenal disorders.

Measurements of basal and stimulated gastric acid secretion, serum gastrin, and serum pepsinogen I cannot replace direct radiologic and endoscopic examination of the gastroduodenal mucosa for diagnosis of peptic ulcer disease, or histological examination for classification of gastritis and duodenitis. These tests, however, can provide information about the functional status of the gastric mucosa and sometimes indicate the etiology of gastric acid hypersecretion. The most diagnostic combination of tests comprises markedly increased fasting serum gastrin, positive serum gastrin response to secretin challenge, and increased levels of basal acid secretion and serum pepsinogen I found in patients with gastrinoma. The same combination of results, except for negative response to secretin and marked stimulation of gastrin by food, is found in patients with antral gastrin cell hyperfunction. Increased serum gastrin concentrations often are found in patients with hyposecretion of gastric acid, including those with atrophic gastritis, and in patients with renal failure, or previous vagotomy. Patients with atrophic gastritis have a low serum pepsinogen I level, while an increased level is found with renal failure and a normal level is found after vagotomy. Thus, the concurrent measurement of serum pepsinogen I and creatinine provides a useful initial step in the evaluation of hypergastrinemia.