Observation of infants with SFU Grades 3–4 hydronephrosis: Worsening drainage with serial diuresis renography indicates surgical intervention and helps prevent loss of renal function

PurposeEarly pyeloplasty is indicated for ureteropelvic junction obstruction (UPJ) obstructions with reduced differential renal function (DRF) and/or no drainage on diuretic renography (DR). Optimal management of Society of Fetal Urology (SFU) Grades 3 and 4hydronephrosis with preservation of DRF and indeterminate drainage is less straightforward. We review our experience using serial DR to guide the management of kidneys with high-grade hydronephrosis, emphasizing preservation of DRF.MethodsAfter IRB approval we reviewed the charts of 1398 patients <1-year-old referred for prenatal hydronephrosis. Only patients with SFU Grades 3 and 4 hydronephrosis without ureterectasis were included in the study. Initial evaluation included a baseline DR. Follow-up included DR or ultrasound (US).Results115 patients (125 kidneys) were eligible for study inclusion. 27 kidneys underwent early surgery (median 64 days) due to reduced DRF and/or severely impaired drainage. 98 kidneys were initially observed. Of these, 21 underwent delayed surgery (median 487 days) due to worsening drainage. Only 2 patients had an irreversible decrease in DRF of >5%. 77 kidneys demonstrated improved drainage and stable DRF. Comparison of observation (n = 77) and surgery groups (n = 48) revealed more kidneys with SFU Grade 3 hydronephrosis in the observation group (p = 0.0001).ConclusionInfants with Grades 3 and 4 hydronephrosis and preserved DRF may be safely followed with serial DR. Patients with SFU Grade 4 hydronephosis are more likely to require surgery. Worsening drainage on serial DR is a useful indicator for surgical intervention which limits the number of pyeloplasties while preserving DRF.