Ectopic kidneys as a source of misinterpretation on bone scintigraphy.

Ectopic kidneys are reported to occur in 1 in 500 to 1 in 1200 of the general population and can be found anywhere from the pelvis to the thorax. Tc-99m methylene diphosphonate (MDP) is a widely used radiopharmaceutical for skeletal scintigraphy and is excreted through the kidneys. The authors present 3 situations in which uptake of Tc-99m MDP in kidneys located at ectopic sites (subsequently confirmed by Tc-99m DMSA scintigraphy) may cause misinterpretation of the bone scan.