Secretin administration induces a dilatation of main pancreatic duct

In this study we evaluated the effect of secretin administration on the caliber of the Wirsung duct visualized by real-time ultrasonography. A maximal dose [75 clinical units (CU)] of secretin was intravenously injected in 1 min into 18 normal subjects. The duct was continuously monitored from the beginning of injection for a period of 20 min and measured at the level of the body using a calibrated optical lens. The mean caliber of the duct (basal value +/- SD = 1.2 +/- 0.4 mm) markedly increased after secretin stimulation (mean value +/- SD at 3 min = 2.9 +/- 0.8 mm). No dilatation was observed in five of these subjects after administration of 2 ml of saline. In a further four subjects a dose of 0.25 CU/kg/hr of secretin caused a much less marked dilatation of the main pancreatic duct. During dilatation a longer segment of duct is more clearly visualized; furthermore the pancreatic juice within the duodenum improves ultrasonographic imaging of the head of the pancreas.