In a group of 44 healthy probands, the change in bile-duct size after ingestion of a gastric stimulant in the early stage of the regulation was examined. From an empty diameter of 5.62 mm, a statistically significant reduction to 4.00 mm was found after 5 min, followed by a further slight reduction to 3.86 mm after 10 min and to 3.57 mm after 20 min. The physiological basis is the influence of cholecystokinin on the ductus hepatocholedochus and the sphincter of Oddi. This eliminates the long examination and observation intervals typical of radiological diagnostics and justifies early functional sonographic investigation of the bile duct during abdominal sonography, which does not involve an additional time investment.