To evaluate the role of urinary lysosomal enzyme N-acetyl-β-D-glucosaminidase (NAG) and brush border enzymes alkaline phosphatase (ALP) and γ-glutamyl transferase (GGT) in the long-term follow-up of children under conservative management for ureteropelvic junction narrowing.

The study included 30 children with dilated nonobstructed kidneys due to unilateral ureteropelvic junction narrowing who were treated conservatively and followed up for 15 months. Voided urine samples were obtained from the children at diagnosis and at 3, 9, and 15 months of follow-up. NAG, ALP, and GGT were measured in these urine samples.

The conservative management of the children during their follow-up period revealed stabilization of renal function in 15 patients (dilated nonobstructed group) and deterioration in 15 (obstructed group). In patients considered to have dilated nonobstructed kidneys, a comparison between the mean values of urinary NAG, ALP, and GGT at the last follow-up and at baseline showed no significant differences. In addition, the mean values of glomerular filtration rate and split renal function showed no significant changes at the last follow-up examination compared with the basal condition. In patients considered to have obstructed kidneys, a comparison between the mean values of the 3 enzymes at diagnosis and at basal condition showed a significant increase in the 3 urinary biomarkers. Moreover, the mean values of the glomerular filtration rate and split renal function showed a significant reduction at diagnosis compared with the basal condition.

NAG, ALP, and GGT are noninvasive biomarkers that could be used for long-term follow-up of children with ureteropelvic junction narrowing under conservative management to determine those who might develop obstruction.