Analysis of duodenal drainage fluid after cholecystokinin (CCK) stimulation in healthy volunteers

Introduction and Aims: Hormonal stimulatory agents are used to assess pancreatic function. Biologically derived secretin, the most widely used pancreatic secretagogue, is no longer available in the United States. Existing secretory tests using cholecystokinin alone are cumbersome, requiring a unique dual tube (gastric and duodenal) collection system and constant perfusion of a nonabsorbable marker to calculate enzyme output (in international units [IU]). A simpler, quantitative cholecystokinin stimulation test that measures enzyme concentrations (in international units per liter [IU/L]) instead of total output would obviate need for marker perfusion/collection. The aim of our experiment was to study the secretory patterns of pancreatic enzyme concentration in duodenal fluid after cholecystokinin stimulation in healthy volunteers. Methodology: Healthy subjects had a Dreiling tube inserted endoscopically into the ligament of Treitz. Gastric and duodenal aspiration ports were connected to low intermittent suction. A 20-minute baseline was obtained to clear the gastric and duodenal lumina of residual fluid. Cholecystokinin was infused at a constant rate of 40 ng/kg per hour. Duodenal fluid was collected on ice for 80 minutes in four 20-minute aliquots. Aspirated fluid was analyzed for enzyme concentration with an automated chemistry analyzer in the hospital biochemistry laboratory. Results: Nineteen healthy volunteers were studied. The mean volume (±SEM) of duodenal fluid collected was 85 ± 4.4 mL (range, 48 to 118 mL). Fluid analysis revealed a significant rise in mean lipase concentration (±SEM) from a baseline of 595,680 ± 11,930 IU/L to a peak of 1,778,847 ± 171,204 IU/L (mean difference = 1,183,167 IU/L; 95% CI= 664,459 IU/L to 1,701,875 IU/L; p < 0.001, Student t test). Increases in amylase concentrations were markedly less pronounced and did not reach statistical significance. Mean peak lipase concentration occurred within 50 minutes of acinar cell stimulation. All patients tolerated tube placement, and there were no episodes of acute pancreatitis or abdominal pain. Conclusions: Pancreatic lipase concentrations in duodenal fluid increase nearly threefold after cholecystokinin stimulation in healthy volunteers. This magnitude of enzyme secretory response may be a marker of pancreatic function and could potentially lead to a more clinically useful and simpler pancreatic function test. This physiologic study serves as the basis for our further investigations of cholecystokinin-stimulated lipase concentrations as a new test in the assessment of pancreatic insufficiency.