Pyelocaliceal diverticulum is a rare abnormality that is usually found accidentally, as in this case, where a bone scan was performed as part of the evaluation for metastic disease. As Tc-99m MDP is excreted by the kidneys, tracer will accumulate in renal collecting system abnormalities, such as pyelocaliceal diverticulum. It is important that tracer accumulation in this lesion not be mistaken for more significant pathology. A case is presented in which focal accumulation of Tc-99m MDP within a pyelocaliceal diverticulum mimicked a rib lesion.
