[Dynamic test in the echographic evaluation of the common bile duct].

Common bile duct (CBD) diameter was measured with ultrasonography in 396 patients (131 had previous cholecystectomy) before and 40 minutes after the ingestion of a fatty meal. CBD diameter reduced in 177 cases, remained unchanged in 175, increased in 44. The increasing of CBD diameter always means obstructive choledochal pathology, caused by stones or other pathologic conditions. Caliber reduction or other pathologic conditions. Caliber reduction is physiologic. When CBD remains unchanged, in 10% of the cases there are stones in the duct.