Surgery versus observation for managing obstructive grade 3 to 4 unilateral hydronephrosis: A report from the society for fetal urology

Purpose: The Society for Fetal Urology has undertaken the first multicenter prospective randomized study of high grade obstructive unilateral hydronephrosis to evaluate the natural history of untreated obstruction and compare it to the benefits of pyeloplasty. Materials and Methods: Since 1991, infants with isolated unilateral Society for Fetal Urology grade 3 hydronephrosis and ipsilateral obstruction with greater than 40% differential renal function on well tempered renography were studied. Patients were randomly assigned to observation or pyeloplasty groups. Renal ultrasound and well tempered renography were performed biannually for 1 year and yearly thereafter. Crossover criteria for surgery included concurrent worsening of isotope washout and increasing grade of hydronephrosis or a greater than 10% point loss in percent differential renal function that was noted between studies. The end point of the study was the 3-year anniversary of randomization. Results: A total of 32 infants from 10 centers were randomized equally to 2 groups. The starting grade of hydronephrosis and percent differential renal function were similar between the 2 groups. At 6 months and 1 year the grade of hydronephrosis was significantly reduced (p < 0.02) and well tempered renography was significantly more likely to demonstrate no obstruction (p < 0.03) in the surgical group compared with the observation group. The mean percent differential renal function remained stable and similar in both groups. Reduced hydronephrosis and resolution of obstruction in the surgery group persisted as a trend at the 2 and 3-year anniversaries. In the observation group 4 patients (25%) showed enough renal deterioration to qualify for crossover to surgery. Conclusions: Infant pyeloplasty significantly improved the grade of hydronephrosis and drainage pattern at 6 months and 1 year postoperatively, when compared with observation. Renal function stabilization was similar for either management approach. However, 25% of the patients satisfied objective criteria of status deterioration requiring pyeloplasty.