Population-specific serum creatinine centiles in neonates with posterior urethral valves already predict long-term renal outcome

Introduction: The lowest serum creatinine (nadir Scr, cut-off 1mg/dl) during infancy predicts subsequent renal outcome in posterior urethral valve (PUV) infants, but early, neonatal values may be useful to guide care. We aimed to explore correlations between neonatal Scr values and long-term renal outcome. Methods: Retrospective evaluation of records of 39 PUV patients, treated in the University Hospitals Leuven (2001-2011). Scr measurements were collected and associations (Mann-Whitney U, Spearman) to predict unfavorable renal outcome [GFR <60ml/min/1.73m at 2 years] were explored. Results: Unfavorable renal outcome at the last follow-up was observed in 7/36 patients (19%). Besides the nadir Scr at a median age of 5 months, also the peak Scr and Scr between days 9 and 42 correlated significantly with renal outcome. By introducing "centiles" for neonatal Scr values in this PUV cohort, the 75th Scr percentile in this PUV cohort was highly predictive for unfavorable renal outcome. Conclusions: Besides the nadir Scr, early neonatal Scr values (peak, days 9-42, PUV cohort-specific 75th centile) also predicted unfavorable renal outcome. The introduction of PUV disease specific reference Scr centiles may be helpful to facilitate earlier prediction and guide counseling, but necessitates external validation.