Neutrophil gelatinase-associated lipocalin (NGAL) value changes before and after shock wave lithotripsy

Our aim was to determine short and medium-term changes of neutrophil gelatinase-associated lipocalin (NGAL) in the urine of patients undergoing shock wave lithotripsy (SWL). In patients with kidney stones, serum urea and creatinine (Cr), urine Cr and NGAL levels were determined immediately before and at 3, 24 h and 30 days after SWL. Urine NGAL concentrations were normalized to urinary Cr ruling out the confounding effect of variable hydration states. Thirty-five patients with a single renal stone were enrolled. Inclusion criteria were: first SWL treatment for each patient, single radiopaque renal stone <20 mm; normal renal function. Exclusion criteria were: body mass index (BMI) > 30 kg/m², recent episodes of renal colic (less than 3 months), the presence of radiolucent stones, renal impairment, upper urinary tract obstruction or malignancy, acute pyelonephritis, patients who consumed potentially nephrotoxic drugs within 4 weeks before the evaluation. Geometric means of urinary NGAL/Cr ratio measured 3 h after SWL were significantly higher than baseline values (difference 7.56 ng/mg, 95% confidence interval 1.61, 13.51; p value = 0.013). No changes were found for urinary NGAL/Cr measured at 24 h (p value = 0.92) and at 30 days (p value = 0.13) after SWL compared with baseline values. Urinary NGAL levels increase soon after SWL (3 h) and quickly return to and maintain basal levels (1 and 30 days). Further studies are necessary to understand the hypothetical role of NGAL as a guide to the degree of tissue injury after SWL.