Complementary role of Tc-99m-diethyl-IDA and ultrasound in large and small duct biliary tract obstruction.

Fifty-one patients underwent both radionuclide and ultrasound studies of the hepatobiliary system. Eleven patients had large bile duct obstruction, six had intrahepatic diffuse small duct obstruction, and 37 had no obstruction. In all 11 patients with large duct obstruction, the radionuclide images were abnormal, but in nine of these studies the level of obstruction could not be determined. Ultrasound was abnormal in nine studies (with correct identification of level), normal in one, and technically inadequate in one, ultrasound scans were also abnormal in six patients without obstruction. In small duct obstruction, the radionuclide scan was abnormal in all six, but in five patients it could not differentiate small from large duct obstruction. In all six patients, ultrasound showed no large duct obstruction, thus allowing identification of the level of obstruction in patients whose radionuclide scans were equivocal. A cost analysis indicated that in suspected large duct obstruction, the best strategy is u...