Extraosseous Metastases Masquerading as Urine Contamination on Bone Scans

Abstract

Urine contamination is probably the most common cause of focal soft-tissue activity in the pelvis, thigh or legs as seen on a radionuclide bone scan. We report two cases of focal soft-tissue activity which were initially thought to represent urine contamination but were later proven to be extraosseous metastases. We present these two cases to illustrate that soft-tissue activity which is presumed to be caused by urine contamination must always be verified by washing off the suspected area and then obtaining an additional image to see if the activity has been removed or persists. This is particularly important in patients with primary malignant bone tumors and in tumors which have a propensity to produce calcification.