Ultrasound diagnosis of multicystic dysplastic kidney: is a confirmatory nuclear medicine scan necessary?

OBJECTIVE: It is critical to differentiate between a multicystic dysplastic kidney (MCDK) and a kidney with severe hydronephrosis as the treatment varies significantly. We designed a study to compare renal ultrasound (RUS) to nuclear medicine (NM) scan in the diagnosis of MCDK, in order to determine if RUS can be used for the definitive diagnosis of MCKD without use of NM scan.

MATERIALS AND METHODS: We performed a retrospective review of children with MCDK, who underwent both a RUS and Tc-99m MAG3 or DMSA scan. We planned to calculate the positive predictive value of an RUS diagnosis of MCDK, using NM scan diagnosis of a nonfunctioning kidney as the gold standard.

RESULTS: The diagnosis of MCDK was made by RUS in 91 patients, 84 of whom had a normal bladder US. NM confirmed the diagnosis of MCDK in all 84 of these patients (100%).

CONCLUSION: We have demonstrated a high predictive value for RUS in the diagnosis of MCDK. Our data support that in healthy infants with RUS diagnosis of unilateral MCDK and normal bladder US, NM scan may be unnecessary to confirm the diagnosis.