[NAG (N-acetyl-beta-D-glucosaminidase)--a sensitive marker for disorders of kidney function].

In a clinical study we tested the use of the lysosomal enzyme NAG as a parameter of kidney function. Following prospective randomization, we examined NAG excretion during cisplatin treatment with/without nephroprotection, after intravenous urography with ionic/non-ionic contrast media, during lower/upper urinary tract infections and before/after extracorporeal shockwave lithotripsy for intrarenal calculi (first-generation equipment used). Measurements were performed in 3-h urine specimens and in urine collected over 24 h, using a simple method of analysis. A correlation between NAG leakage and functional disorder of the renal tubular cells seemed likely on the basis of additional clinical and experimental data. Increases, in some cases dramatic, in NAG excretion were observed after the administration of cisplatin and ionic contrast media, in acute pyelonephritis, and after extracorporeal shockwave lithotripsy. However, the increase in NAG excretion was less impressive during cisplatin therapy when nephroprotective amino acids were infused, and in the urography group when non-ionic contrast media were used. Infections of the lower urinary tract did not increase NAG excretion. The results indicate that NAG is a sensitive marker of occult renal dysfunction, which can be checked by non-invasive techniques and can be used in a clinic setting to detect functional disorders of the kidney.