FALSE-POSITIVE WHOLE-BODY I-131 SCAN DUE TO INTRAHEPATIC DUCT DILATATION

Focal retention of radioactivity in the liver on whole-body I-131 scan was interpreted as a metastatic lesion in a patient with well-differe ntiated thyroid cancer. Intrahepatic duct dilatation, usually resultin g from biliary tract obstruction by bile stone, is a common disorder a nd may cause bile stasis. A patient with papillary thyroid cancer and a previous history of biliary tract stones had focal retention of radi oactivity in the liver on whole-body I-131 scan. Abdominal CT, endosco pic retrograde cholagiopancreatography, radionuclide cholangiography a nd sequential I-131 scans demonstrated that this focal retention of ra dioactivity was caused by intrahepatic duct dilatation. Focal retentio n of radioactivity is visualized on delayed images but not on early im ages. The radioactivity initially increases and then decreases on foll owing days.