Materials and MethodsSonography was performed on 203 children with a real-time mechanical sector scanner, either a Diasonics Wide-vue using a 3.5, 5, or 7.5 MHz transducer or a Diasonics Neonatal Unit using a 6 MHz transducer. Indications for study included: urinary tract infection (77 patients), "screening" (77 patients with abnormal urinalysis, enuresis, anindia, scoliosis, undescended testicle, or other problems), spinal abnormality (1 8), abdominal pain (13), question of sepsis (six), question of mass (four), gastrointestinal abnormality (four), and hypertension (four). Patients were excluded from consideration if they had a history of malignancy, use of steroids, upper urinary tract abnormality, vesicoureteric reflux (greater than grade 1), or urologic surgery, or if the sonography of the kidneys was considered abnormal (e.g., hydronephrosis, dysplastic kidney, solitary kidney). Recognized duplex kidneys were also excluded.The ultrasonic transducer was positioned to image the kidney in its longest dimension ( fig. 1), and the renal lengths reported here were measured with mechanical calipers from the hard-copy transparencies exposed at the time of study. The patients' ages were recorded to the closest month for those older than 1 year and to the closest week for those younger than 1 year. Weight, height, and body surface area were not recorded for all patients and could not be used for statistical analysis. The 203 patIents ranged in age from several hours to 1 9 years; figure 2 shows
