In 43 patients with various hepatobiliary disorders, we compared retrospectively the sensitivity and specificity of hepatobiliary scintigraphy and ultrasonography in diagnosing extrahepatic biliary obstruction. Hepatic uptake of radioactivity from the circulation was assessed by early scintiscan at 2 min, and the clearance ratio was combined with transit time in the interpretation of hepatobiliary scintiscans. The transit time was defined as the time taken by detectable radioactivity to appear in the extrahepatic biliary tree or small intestine, whichever occurred sooner. The sensitivity and specificity were 92% and 97%, respectively. However, the specificity dropped to 74% when biliary-bowel transit time, i.e., time taken for detectable radioactivity to appear in small intestine only, was used instead of transit time in the interpretation of the scintiscans. The sensitivity and specificity of ultrasonography were 55% and 94%, respectively. We conclude that hepatobiliary scintiscan is more sensitive than ultrasonography and is reliable for diagnosing extrahepatic biliary obstruction when it is done and interpreted by the method described here.
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