Skeletal nonvisualization in a bone scan secondary to intravenous etidronate therapy.

Etidronate disodium (EHDP) therapy is often instituted emergently for treatment of hypercalcemia associated with malignancy, and a staging bone scan is part of the evaluation of the patient with extensive metastatic disease. In these patients in whom high dose EHDP therapy has been instituted, uptake of the bone scan agent is markedly diminished. The case presented illustrates this finding: a breast cancer patient who had received two 500-mg intravenous doses of EHDP prior to bone scan staging. No skeletal visualization was present at 3 hr after 99mTc-MDP injection. Blood-pool activity and uptake in large metastatic sites were observed.