False-positive liver scan due to ascites.

Extrahepatic structures (breast, costal margin, kidney, pleural effusion, right lower lobe lung mass) may occasionally result in a false-positive liver scan by causing attenuation of the gamma rays emenating from the liver, thereby simulating an apparent intrahepatic lesion. A false-positive diagnosis of intrahepatic pathology may often be avoided by simple maneuvers such as elevating the breast, obtaining another projection, etc. A case of false-positive liver scan due to loculated ascites is presented in which these maneuvers failed to resolve the problem. Ultrasound or CT examination may be helpful in this circumstance due to the cross-sectional nature of the information they provide.