The day of contamination.

OBJECTIVE We present 3 cases of suspected radioisotope urinary contamination that occurred on a single day. Because net clearance is via the kidneys, the injected dose is excreted in patients' urine. It is important to recognize the patterns of urinary contamination to avoid reporting false-positive abnormalities. MATERIALS AND METHODS (99m)Tc-Medronate was administered intravenously and whole-body bone scans and spot views were obtained 2-3 h later. RESULTS Two cases of urinary contamination were confirmed, and the third case was false-positive with a urinary collection leg bag seen in an orthogonal view. CONCLUSION We believe that urinary contamination is probably the most common type of contamination. There are distinct urinary contamination patterns among male and female patients. It is unusual to find so many cases of contamination on a single day in our institution. Few statistics are widely available on the number or percentages of contamination for specific radiopharmaceuticals.