Focal areas of increased renal tracer uptake on bone scans can mimic metastases in the lower ribs.

Focal renal concentration of radioactivity can simulate metastatic deposits in the lower ribs on bone scintigrams. 400 consecutive bone scintigrams were reviewed for focal areas of increased tracer activity in the kidneys. 62 patients (15.5%) had at least one renal hot spot. In 42 of these 62 patients (67.7%) there was an increased focal uptake in the left kidney (18 upper pole, 18 middle pole and six lower pole). 50 out of 62 bone scans (80.7%) showed increased activity in the right kidney (14 upper pole, 32 middle pole and four lower pole). With the incidence of focal areas of activity in the upper poles of the kidneys being 8%, the interpretation of a single focal abnormality projected over the lower ribs should be made with particular care, especially in cancer patients.