Bone scintigraphy hot-spot in projection to rib and kidney: role of single photon emission computer tomography/computer tomography in distinguishing a urine collection in renal calyx from a metastasis to rib.

On planar bone scintigrams, activity enhancement foci in projection to kidney and lower ribs can arise from the kidney, or from bone lesions. A differentiation based only on the exact location and shape of the hot spot can sometimes be misleading, resulting in a false qualification of a rib metastatic lesion as urine collection in the kidney or opposite. The authors illustrate the problem with three cases: In two patients, such a hot spot appeared to be the solitary metastatic focus; in one, highly suggestive for solitary metastatic focus, it was proven to be a urine collection.