Secretin-induced plasma bicarbonate decrease as a simple indicator of exocrine pancreatic function

During a secretin-cerulein test for exocrine pancreatic function, venous acid-base analysis was performed before and 30 and 45 min after the intravenous injection of secretin (1 clinical unit/kg body weight). A decrease in plasma bicarbonate was observed in persons with normal exocrine pancreatic function as defined by normal bicarbonate and enzyme secretion in the secretin-cerulein test (n = 39). Bicarbonate values were 94.8 +/- 3.6% (mean +/- SD) of the initial concentration after 30 min and 92.9 +/- 3.9% after 45 min. In contrast, there was no statistically significant decrease in plasma bicarbonate in patients with global pancreatic exocrine deficiency (n = 15). In normal exocrine pancreatic function, the maximal plasma bicarbonate decrease was 2.17 +/- 1.12 mM (mean +/- SD; n = 39). In patients with global exocrine deficiency, however, a maximal plasma bicarbonate decrease of 0.54 +/- 0.68 mM (n = 15) was obtained. The difference was highly significant (p0.001). In patients with partial exocrine deficiency (isolated decrease in bicarbonate secretion or reduced excretion of a single enzyme), values were also significantly lower (1.44 +/- 1.40 mM; n = 14; p0.05). The maximal plasma bicarbonate decrease correlated with the bicarbonate secretion into the duodenal juice (r = 0.62, p0.001). If a maximal plasma bicarbonate decreaseor = 0.9 mM was considered normal, determination of plasma bicarbonate following secretin administration allowed us to detect the presence of global exocrine deficiency with a sensitivity of 87% and a specificity of 87%. The secretin-induced plasma bicarbonate decrease may therefore be used as a new simple tubeless test to evaluate exocrine pancreatic function.