Evaluation of renal-skeleton ratio of technetium-99m phosphonate in multiple myeloma

The kidneys were evaluated on [99mTc]phosphonate bone scans using 35 studies from 23 individuals with multiple myeloma; these images were compared with those from 50 controls. In each case, the kidneys could be visualized and calculation was made of the renal:skeleton ratio. Two myeloma patients showed an elevated renal:skeleton ratio. One was due to reduced vertebral uptake of [99mTc]phosphonate following therapeutic radiation. In the second case, the elevated ratio was related to renal uptake of the tracer (independent of urinary retention), and was consistent with nephrocalcinosis. No significant correlation between the renal:skeleton ratio and the degree of hypercalcemia, proteinuria, or renal impairment was found. We conclude that bone scintigraphy represents a safe, simple means of demonstrating renal presence and activity in multiple myeloma patients. However, calculation of the renal:skeleton ratio is not directly helpful in clarifying the events of calcium metabolism.