Unchanged size of a dilated common bile duct after a fatty meal: results and significance.

Sonographic measurement of common bile duct caliber alone is insufficient to ascertain the presence of obstruction. Fatty meal stimulation significantly improves diagnostic accuracy. An increase in caliber of a normal or slightly dilated common duct after the subject has ingested a fatty meal is a strong indicator of biliary obstruction, while a decrease in caliber indicates normal dynamics and virtually excludes obstruction. This study determines the significance of no change in the caliber of the dilated common bile duct of subjects who have eaten a fatty meal. Further imaging studies and clinical/laboratory follow-up of 31 patients showed that in 84% of the cases no obstruction was present. A dilated common duct that does not decrease in size after a fatty meal is not a specific indicator of obstruction. The use of invasive diagnostic procedures in these patients is not advised unless there is other evidence of biliary obstruction.