Urinary N-acetyl-beta-glucosaminidase in children with idiopathic nephrotic syndrome

Twenty-one nephrotic children, aged 2 to 15 years, were studied for their urinary N-acetyl-beta-glucosaminidase (NAG) and daily urinary total protein, in a total of 35 episodes. Among them, 18 patients had urinary NAG levels (77.3 +/- 112.1 u/g Cr) above normal mean + 2 SD for age, while 3 had normal levels during the nephrotic stage. No or poor correlation was found between urinary protein and NAG. In eight of these patients, urinary NAG levels during heavy proteinuria and after remission were evaluated. No significant change was detected. These observations suggest that urinary NAG excretion in nephrotic children is not caused by an increased glomerular permeability to macromolecules. Instead, the elevated urinary NAG may reflect the activity of associated renal tubular dysfunction or tubulointerstitial involvement in the nephrotic syndrome.