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Summary Introduction The diagnosis of renal function impairment and deterioration in congenital urinary tract obstruction (UTO) continues to be extremely challenging. The use of new renal biomarkers in this setting may favor early renal injury detection, allowing for a reliable choice of optimal therapeutic options and the prevention or minimization of definitive renal damage. Objective The aim of the study was to investigate a selection of promising biomarkers of renal injury with the intention of evaluating and comparing their profile with clinically based decisions for surgical intervention of infants with congenital obstructive uropathies. Study design The first-year profile of renal biomarkers, serum creatinine (sCr), serum and urine cystatin C (CyC), neutrophil gelatinase–associated lipocalin (NGAL), kidney injury molecule-1 (KIM-1), transforming growth factor beta-1 (TGF-β1), retinol-binding protein (RBP), and microalbuminuria (μALB), was analyzed in a cohort of 37 infants with congenital UTO, divided into three subgroups, 14 cases with grade III unilateral hydro(uretero)nephrosis, 13 cases with grade III bilateral hydro(uretero)nephrosis, and 10 cases with low urinary tract obstruction (LUTO), compared with 24 healthy infants matched by gestational age and birth weight. Serum and urine samples were stored at −70 °C and thereafter analyzed by quantitative enzymatic immunoassay. Results Compared with the control group (Figure), all renal biomarker values were significantly increased in patients (P ≤ 0.02). In the unilateral hydronephrosis and LUTO group, RBP (P ≤ 0.043), NGAL (P ≤ 0.043), KIM-1 (P ≤ 0.03), and TGF-β1 (P ≤ 0.034) values dropped significantly after surgery. Neutrophil gelatinase–associated lipocalin alone and in combination with urine and serum CyC demonstrated the best performance in determining the need for surgery (area under the curve, 0.801 and 0.881, respectively). Biomarker profile analysis was suggestive of surgical intervention in 55.4% (7/13) of non-operated cases, and most of the biomarker values were above the cutoff levels within at least 3 months before the clinically based surgical decision in 58% (14/24) of all operated patients. Discussion To the best of the authors' knowledge, this is the first study to present the clinical use of selected group of serum and urinary biomarkers in the setting of UTO to distinguish between patients who would benefit from surgery intervention. The most promising results were obtained using NGAL, RBP, TGF-β1, and KIM-1, especially in the unilateral hydro(uretero)nephrosis and LUTO subgroups when compared with the control group. Conclusions Urine biomarkers, alone and in combination, demonstrated high potential as a non-invasive diagnostic tool for identifying infants who may benefit from earlier surgical intervention. Download : Download high-res image (117KB) Download : Download full-size image Figure . Comparative analysis of pre-operative values of the urine biomarkers in operated patients and control participants at the age of 12 months. The significance of all values was verified by the Student t-test for paired data and by the ¶) Wilcoxon signed-rank test for paired data. The median for urine biomarker sampling was 7 (3–59) days before surgery, in operated patients. KIM-1, kidney injury molecule-1; NGAL, neutrophil gelatinase–associated lipocalin; RBP, retinol-binding protein; TGF-β1, transforming growth factor beta-1; uCyC, urine cystatin C; μALB, microalbuminuria; uCr, urine creatinine.