Unexpected regeneration of a congenital unilateral hypoplastic-dysplastic kidney after contralateral tumornephrectomy

The congenital hypoplastic-dysplastic kidney is characterized by a signific ant reduction of renal mass, an abnormal parenchymal differentiation and is associated with anomalies of the whole urinary tract. Not much is known ab out the ability for regeneration in such a kidney. We report on a 2 year 11 months old boy with an anaplastic Wilms tumor of t he left kidney, in whom after tumor-nephrectomy an unexpected functional an d sonographically documented morphological regeneration of the contralatera l hypoplastic-dysplastic kidney occurred. The regeneration of this kidney i s especially notable, because it occurred during nephrotoxic chemotherapy a nd radiotherapy.