[en] A 5-wk-old male presented with radiographic findings of a duplicated collecting system. A [/sup 99m/Tc]DMSA scan was requested to evaluate cortical function. Images obtained immediately. postinjection showed activity restricted to the upper poles; in contrast, delayed images at 4 hr showed activity in the bladder and throughout both kidneys. Catheterizing the patient drained the activity from the bladder but had little effect on the refluxed renal activity. The early [/sup 99m/Tc]DMSA images were critical in making the proper interpretation. Technetium-99m DMSA is excreted into the urine and this fact needs to be considered when interpreting scans of patients with possible reflux or obstruction. When DMSA scans are obtained in pediatric patients with possible reflux, catheterization prior to the study and early images prior to the appearance of DMSA in the collecting system are recommended