Congenital Solitary Kidney in Children: Size matters.

PURPOSE: To assess renal function outcome in children with congenital solitary kidney and evaluate prognostic risk factors. PATIENTS AND METHODS: Retrospective multicenter study on children with congenital solitary kidney, evaluated between January 2009 and October 2012 in 2 pediatric nephrology and 5 pediatric units. Children aged 0-18 years with a congenital solitary kidney confirmed by scintigraphy were enrolled. We examined the clinical charts of 210 children, 146 were suitable for analysis. Median follow-up was 4.6 years. Primary outcome was decreased estimated glomerular filtration rate, secondary outcome was occurence of proteinuria and/or systemic hypertension. A primary outcome free survival analysis was performed, including a multiple regression analysis of significant risk factors. RESULTS: The primary outcome was present in 12% of children at a median age of 2.2 years. The primary outcome free survival analysis revealed an estimated event free survival of 82% (95% CI 74-91%) at 10 years; the estimated survival was significantly lower in children with additional congenital anomalies of the kidney/urinary tract (54 vs 88%) or insufficient renal length versus expected for a normal CSK; the latter was the strongest predictor of lower estimated outcome free survival (49 vs 89%, p<0.001). Secondary outcomes were present in <5% of children. CONCLUSIONS: Some children with congenital solitary kidney show decreased glomerular filtration rate; associated anomalies of the kidney/urinary tract or insufficient renal length appear as significant risk factors. Adequate length of the congenital solitary kidney is a key parameter for maintenance of renal function and should be examined routinely during follow-up.