Is Urinary Kidney Injury Molecule-1 a Noninvasive Marker for Renal Scarring in Children With Vesicoureteral Reflux?

Abstract

To examine whether (1) levels of urinary kidney injury molecule-1 (KIM-1), a transmembrane protein and biomarker for renal tubular damage, increase in children with of vesicoureteral reflux (VUR), and (2) if KIM-1 predicts the grade of renal scarring in children with VUR. The study included 59 VUR patients with renal scarring, 5 VUR patients without renal scarring and 25 healthy controls aged 1 to 17 years. Dimercaptosuccinic acid scans were performed for determination of scarring and graded by 3 independent, blinded pediatric urologists for renal scarring according to the Randomized Intervention for Children with VUR study criteria. Spot urine samples were obtained. Urinary KIM-1 and creatinine levels were measured and the KIM-1/creatinine ratio was calculated. Urine geometric mean KIM-1 levels (ng/mg creatinine) were significantly higher in VUR patients than in healthy controls (P=.018). Although the correlation between VUR grade and geometric mean KIM-1 levels was not significant, a positive correlation was found for scarring grade and geometric mean KIM-1 levels (r=.30, P=.02). When the patients were divided by subgroups according to scarring grade (group I, grade 1; group II, grades 2 and 3; group III, grade 4), the log KIM-1 in group III was significantly higher than in group I (P=.004). Urinary KIM-1 levels might be used as a noninvasive marker, particularly in showing severe scarring in children with VUR.