Multilocular cystic nephroma. Preoperative diagnosis with CAT

: We report a case of multilocular cystic nephroma in a 45-year-old female patient who had been referred for urological evaluation on detecting a mass in the left lumbar region. Patient work up included CT evaluation, which proved to be the most useful in making the diagnosis. The literature is reviewed with special reference to the nature of this lesion and the existing controversy on whether it is an embryonary tumor or a congenital malformation.