Is urinary N-acetyl-beta-D-glucosaminidase a marker of urological abnormality in children?

Background: Hydronephrosis is the most common congenital condition that is detected by prenatal ultrasonography. Moreover, the widespread use of prenatal ultrasonography results in an increased recognition of fetal hydronephrosis. Prenatal hydronephrosis is diagnosed at an incidence of 1:100 to 1:500 by ultrasonographic studies. The presence of hydronephrosis is not synonymous with obstruction. Obstruction signifies impairment of urinary flow, which if left untreated will cause progressive deterioration of renal function. Approximately 10-20% patients with obstruction show progression of hydronephrosis or worsening renal functions. Methods: The study population consisted of 72 patients who were referred to the Division of Pediatric Nephrology, Mofid Children's Hospital, Tehran, IRAN for evaluation and treatment of pyelonephritis. All patients underwent two-dimensional ultrasonography (2D US) of the urinary tract; immediately afterward. Diagnosis of pyelonephritis has been based on clinical and paraclinical findings and abnormal 99mTc- demercaptosuccinic acid scan (DMSA scan). Glomerular filtration rate was in normal range in all of them. The children were classified in two groups as having normal kidney ultrasonography and abnormal ultrasonography. Fresh random urine samples were obtained on the admission time and at 48th hour of treatment. Urine samples were tested for N-acetyl-betaD-glucosaminidase (NAG) (ELISA colorimetric, DIAZYME, USA) and creatinine. All of our patients were treated with same medication. We also evaluated our patients with voiding cyctoureterography (VCUG), renal scintigraphy and biochemical studies. Results: In this study 73.6% of the patients had normal ultrasonography and 26.4% abnormal ultrasonography. In patients with abnormal kidney ultrasonography, condition such as stasis, moderate to severe hydronephrosis, decreased cortical thickening and urinary stone were seen in 47.4%, 26.3%, 5.3% and 21.17%, respectively. The mean for urinary NAG/Creatinine before antibiotic therapy was 36.79 ± 42.24 U/g creatinine in patients with normal ultrasonography, and 46.22 ± 57.53 U/g creatinine in abnormal group. Patients with hydronephrosis had the highest level of urinary NAG (p-value<0.043) and patients with urinary stone, had the lowest level of urinary NAG (p-value<0.004). Conclusion: The urinary NAG was elevated in children with urinary tract abnormality with or without infection. Hense this protein could be a useful marker in prediction of hydronephrosis and its renal damage in pediatric group, although studies with greater numbers of patients are needed to establish this opinion.