Patterns of intrahepatic bile duct dilatation at CT: correlation with obstructive disease processes

The authors performed a blinded, retrospective analysis of 100 computed tomographic (CT) scans of patients with proved extrahepatic bile duct obstruction, including primary sclerosing cholangitis (PSC), to determine whether certain patterns of intrahepatic bile duct dilatation are suggestive of specific disease processes. Among 30 patients with benign obstructive disease, CT showed pruning of the intrahepatic ducts in four patients (13%), beading in four (13%), and skip dilatations in one (3%). Among 54 patients with malignant obstructive disease, CT illustrated pruning in eight (15%) patients, beading in 11 (20%), and skip dilatations in two (4%). Among 16 patients with PSC, CT demonstrated pruning in four (25%), beading in two (13%), and skip dilatations in five (31%). The majority of patients with malignant or benign obstructive disease or PSC had intrahepatic duct dilatation in both lobes of the liver. It extended into the periphery in 46 of 54 patients (85%) with malignant obstructive disease, in 20 of 30 (67%) with benign obstructive disease, and in 10 of 16 (63%) with PSC. The CT finding of skip dilatations is strongly suggestive of PSC. The CT findings of pruning and beading are nonspecific and may be observed at CT in patients with bile duct obstruction due to a wide variety of causes. The distribution and extent of intrahepatic duct dilatation at CT do not differ among biliary disease processes.