Radionuclide imaging of the biliary tract.

Cholescintigraphy with technetium-labeled biliary agents has great value in evaluation of the patient with suspected acute cholecystitis. Visualization of the gall bladder virtually excludes acute cholecystitis and obstruction of the cystic duct. Nonvisualization of the gall bladder, however, is not specific for acute cholecystitis and may also occur in some patients with chronic cholecystitis or pancreatitis. Interpretation of gall bladder nonvisualization, therefore, must be correlated with the clinical presentation. Biliary tract imaging is also useful in evaluation of some focal abnormalities within the liver, neonatal jaundice, detection of bile leaks or bile reflux, and biliary-enteric shunts. The role of technetium-labeled biliary agents in the evaluation of patients with jaundice is less clear. Excretion of tracer into the gut excludes complete biliary tract obstruction, but the test may be nonconclusive at higher serum bilirubin levels. If persistent common bile duct activity is observed with delayed excretion into the gut, the diagnosis of partial obstruction may be made, but this procedure will be inconclusive if the common bile duct is not visualized and/or significant hepatocellular disease is present. Ultrasonography and abdominal CT are the preferred tools for the diagnosis of biliary tract obstruction at present, but newer biliary tract agents which achieve better hepatic extraction and greater bile concentration at high serum bilirubin levels may improve the diagnostic efficacy of cholescintigraphy.