[A study on acute renal damage from percutaneous nephrolithotomy assessed by urinary NAG and gamma-GTP activities]

We performed percutaneous nephrolithotomy (PNL) on 49 patients between May, 1986 and March, 1987. To investigate acute renal damage from PNL, we measured urinary NAG (N-acetyl-beta-D-glucosaminidase) and gamma-GTP (gamma-glutamyl transpeptidase) activities before PNL and for 6 days after PNL in 24 patients. The NAG activities elevated beyond normal level in 23 patients and gamma-GTP activities in 15 patients. NAG activities showed a peak level in the third day after PNL and gamma-GTP activities in the next day of PNL. After the peak both enzyme activities got down gradually. There was no difference in NAG and gamma-GTP activities between nephrostomy and lithotripsy in 2 staged patients. And the intrapelvic pressure during operation was at the normal level in 5 patients. Therefore, we think that the cause of NAG and gamma-GTP activity elevation is a mechanical damage, not an influence of the irrigation fluid. Large stones, long operation time and 2 stage procedure were the factors that produced high enzyme activities, because, we guess, the frequency of mechanical damages to the kidney increase in such cases. Postoperative pyrexia caused a slight increase in enzyme activities but preoperative hydronephrosis exerted no influence on both enzyme activities. We also measured creatinine clearance before and after PNL but no significant change was obtained. PNL causes only slight mechanical damage to the operated kidney which is reversible when assessed by NAG and gamma-GTP activities and the glomerular function is not affected. Therefore, we conclude that PNL is a safe treatment for upper urinary tract stones.