In cases attending regular follow-ups, preoperative and postoperative 1st year DMSA results and amount of pelvicaliceal dilatation in the IVU of the unit that underwent surgery were compared statistically (by counting the dots falling on the pelvis and calices using stereologic methods which use transparent acetates with 3-mm inter-grid distances. Inter-IVU image differences between IVUs taken at different centers were resolved by using the value found by counting the dots falling on the 4th lumbar vertebra in both films and proportioning the results with each other as the multiplier. Measurable values were expressed as means + standard deviation.