Magnetic resonance urography: a new gold standard for the evaluation of solitary kidneys and renal buds?

PURPOSE We evaluated the diagnostic potential of magnetic resonance urography (MRU) in pediatric patients with a solitary kidney and/or dysplastic orthotopic or ectopic renal buds. We present our evolving experience with this imaging procedure. MATERIALS AND METHODS A total of 30 patients with a mean age of 43.8 months with a known or suspected solitary kidney with or without clinical symptoms underwent ultrasound of the urinary tract as well as voiding cystourethrogram, renal static dimercapto-succinic acid (DMSA) scintigraphy and MRU. The results of these diagnostic imaging studies were then compared with each other and set against the results of the final diagnosis established at surgery and by histology, if available. RESULTS Dysplastic orthotopic or dystopic renal buds suspected on ultrasound in 11 of the 30 patients were confirmed in all 11 by MRU. While accompanying ectopic ureteral insertions were shown in only 3 patients by ultrasound, they were visualized in all 4 by MRU. The other 7 patients with dysplastic renal buds had orthotopic ureteral orifices. DMSA scintigraphy failed to detect 10 renal buds. CONCLUSIONS The diagnostic value of MRU appears to be superior to that of other imaging tests, even to that of DMSA scintigraphy, which with voiding cystourethrography is currently considered the gold standard for evaluating sonographically suspected solitary kidneys with contralateral orthotopic or ectopic renal buds and ectopic ureteral insertion.