Serendipitous gallbladder uptake in a bone scan.

Ectopic or serendipitous uptake of radiotracer can be a source of diagnostic confusion. A case is presented in which a bone scan showed accumulation of Tc-99m MDP in the gallbladder that initially was interpreted as the right kidney. The exact cause of gallbladder excretion of derivatives of Tc-99m MDP is not known. Our experience suggests that this is a rare finding and is not the result of the quality of radiopharmaceutical injected because none of the other patients injected with the same batch of Tc-99m or MDP kit showed gallbladder or abnormal intestinal excretion.