Urinary enzymes and microalbuminuria as biomarkers of renal dysfunction after contrast administration

Background: Contrast-induced nephropathy (CIN) is a common complication after administration of intravenous iodinated contrast media. The present study evaluated the usefulness of urinary beta-N-acetyl D-glucosaminidase (u-NAG), alkaline phosphatase (u-ALP) and lactate dehydrogenase (u-LDH) as markers of tubular injury and urinary microalbumin (u-MA) as a marker of glomerular injury for early diagnosis of CIN in patients undergoing coronary interventions. Methods: One hundred and twenty patients scheduled for elective coronary angiography (CAG), with or without angioplasty with baseline serum creatinine less than 1.2 mg/dL were recruited. Serum creatinine, u-NAG, u-ALP, u-LDH and u-MA were analyzed at 0, 4 and 24 hours after administration of low-osmolal, non-ionic contrast medium. Results: CIN developed in 27 (22.5%) patients. A significant increase in u-ALP, u-LDH and in u-MA was seen in both CIN and non-CIN groups. However, no significant difference was observed in these markers between the two groups. A significant increase in u-NAG was observed only in the CIN group. Conclusions: Low osmolal, non-ionic contrast medium produced toxic insult to the glomeruli as well as renal tubules even in patients with normal baseline renal function and u-NAG can differentiate patients with CIN.