An Evaluation of the Nephrotoxic Effects of Nonionic Low Osmolality Contrast Media Using Urinary Enzymes

Abstract

A prospective clinical study was conducted to examine the usefulness of urinary enzymes as a sensitive parameter for determining nephrotoxicity caused by LOCM. Forty-seven patients were intravenously injected with 100 ml of LOCM (iohexol or iopamidol) in radiographic studies. Serum creatinine and creatinine clearance (Ccr) were determined before and 7 days after LOCM infusion. Urinary excretion of N-acetyl-β-D-glucosaminidase (NAG) and γ-glutamyltransferase (γ-GTP) was determined before and 1, 2, 3 and 7 days after LOCM administration. To analyze the relationship between the nephrotoxic effect of LOCM and renal function, patients were divided into group L (Ccr<70 ml/min, n = 19) and group N (Ccr≥70 ml/min, n = 28). No significant changes were noted in serum creatinine or Ccr in either group. Urinary NAG and γ-GTP levels were significantly elevated on day 1 compared with the levels prior to LOCM infusion, but these returned to the base line after day 2. The increase ratio of urinary NAG in group L was significantly higher than that in group N on days 3 and 7. No statistical difference between groups L and N was observed regarding urinary γ-GTP increases on any of the days. In conclusion, urinary enzymes are sensitive and useful indicators for evaluating contrast media nephrotoxicity, which cannot be detected by serum creatinine or Ccr. Careful attention should be paid in radiographic studies to patients with renal dysfunction, even when LOCM is being employed.