Ultrasound has been reported to detect metastatic liver tumor in approximately 85%-90% of patients (literature range, 63%-96%, with some of the lower figures being earlier ones). Computerized tomography (CT) has a sensitivity of 90%-95%. Radionuclide scans detect a few more patients with diffuse liver abnormality than CT or ultrasound. However, CT and ultrasound can differentiate cysts from solid lesions in the liver, which both look the same on radionuclide scanning. CT can also detect abnormalities outside the liver as incidental findings to a liver study. Ribs may interfere with ultrasound examination of the liver dome area, and gas in the hepatic flexure of the colon can interfere in the lower area of the liver. Magnetic resonance imaging (MRI) has about the same detection rate as CT but is much more expensive and at times has some problems with liver motion due to relatively slow scan speed.

CT and ultrasound are important aids in differentiating extrahepatic from intrahepatic biliary tract obstruction through visualization of the diameter of the intrahepatic and common bile ducts. In complete extrahepatic obstruction, after a few days the common bile duct becomes dilated; in most cases the intrahepatic ducts eventually also become dilated. In intrahepatic obstruction the common bile duct is not dilated. Ultrasound has asensitivity of about 93% (literature range, 77%-100%), and CT is reported to have a sensitivity of about 94% (literature range, 85%-98%). There have also been considerable advances in the ability of ultrasound and CT to demonstrate the approximate location of obstruction in the biliary system as well as making an overall diagnosis of obstruction. Gas in the intestine may interfere with ultrasound in a few cases.

In general, most investigators believe that ultrasound is the procedure of choice in possible biliary tract obstruction; those few cases that are equivocal or technically inadequate with ultrasound can be studied by CT or some other technique such as percutaneous transhepatic cholangiography.