Article Urinary Biomarkers in Obstructive Nephropathy

Background and objectives Obstructive nephropathy is a leading cause of CKD in children. The assessment of severity of renal impairment and the prediction of which children will progress to renal failure are, however, challenging. Design, Setting, Participants, & Measurements This case-control study measured the urinary excretion of candidate biomarkers in 27 prevalent case-patients with posterior urethral valves (PUVs) and 20 age-matched controls, correlated their urinary concentration with GFR, and analyzed receiver-operating characteristic (ROC) curve and regression analyses to assess their performance as tests for low GFR. Results The median urinary protein-to-creatinine ratio was higher in children with PUV (45 g/mol; range, 5–361 g/mol) than in controls (7 g/mol; range, 3–43 g/mol) (P,0.01) and correlated inversely with renal function (r =20.44; P,0.05). In whole urine, excretion of aquaporin-2 was significantly decreased, whereas that of TGFb and L1 cell adhesion molecule (L1CAM) was significantly increased. Whole-urine TGFb excretion correlated inversely with GFR (r =20.53; P,0.05). As tests for low GFR, whole-urine TGFb, L1CAM, and urinary protein-to-creatinine ratio performed best, with areas under the ROC curves of 0.788, 0.795, and 0.814, respectively. By linear regression analysis, whole-urine TGFb, L1CAM, and urinary protein-to-creatinine ratio were associated with low GFR in the case-patients. Conclusions Candidate biomarkers of obstructive nephropathy can be readily measured in whole urine and in urine exosomes. In boys with PUV, these biomarkers correlate with GFR