CLINICAL HISTORY.—A girl, 4 months of age, was admitted to the Los Angeles Childrens Hospital because of a left flank mass. The latter was first noted by the mother three days before while bathing the infant. On the evening of admission, the child had a generalized seizure with a temperature of 104 F (40 C). The child's past history had not been remarkable, and she had progressed normally in her physical and motor landmarks.
On admission to the hospital the infant was alert and robust. A large firm mass was palpable in the left flank. No other abnormalities were detected in the physical examination. Numerous WBC with some RBC were present in the urine. No significant abnormalities were found in the hemogram, cerebral spinal fluid tests, or skull radiographs. An intravenous urogram was performed on the day of admission (Fig 1). No calcifications were present on the preliminary film of