Sonographic measurement of the extrahepatic bile duct before and after retrograde cholangiography.

The maximum diameter of the extrahepatic bile duct visible on cholesonograms was measured immediately before and immediately after endoscopic retrograde cannulation and injection of the biliary and pancreatic ducts (ERCP) in 24 patients. Sonographic bile duct diameter increased by 3 mm or more in nine patients, all of whom had had a previous cholecystectomy. Bile duct diameter was unchanged in the remaining 15 patients, six of whom had had cholecystectomy. The technical performance of ERCP alone will alter bile duct diameter in a significant proportion of patients having endoscopic cannulation of the biliary tree. This is particularly so for patients who have had their gallbladders removed. The true diameter of the extrahepatic bile duct cannot be determined in many patients by simple measurement of images obtained at ERCP, even when corrections are made for radiographic magnification.