Factors affecting the incidence of contrast-induced nephropathy in patients undergoing computed tomography.

Objective: To analyze the incidence of contrast-induced nephropathy in a cohort of patients undergoing computed tomography (CT) with intravenous iodinated contrast material. To evaluate the efficacy of N-acetylcysteine in preventing contrast-induced nephropathy.

Patients And Methods: This prospective observational study was carried out in the months comprising March 2016 through July 2016. We selected the first five patients scheduled to undergo CT examination each day who agreed to participate and signed the informed consent form. We recorded patients' cardiovascular histories, chronic treatments, and indications for the CT examination. We measured blood levels of creatinine and urea before and after the CT examination. We used the Modification of Diet in Renal Disease (MDRD-4) equation to estimate the glomerular filtration rate. We analyzed the type and dose of contrast material. We recorded whether N-acetylcysteine was administered before the CT examination. We used SPSS 15.0 to compare means and proportions. Statistical significance was set at p < 0.05.

Results: No incidents of contrast-induced nephropathy were detected in any of the 202 patients included [mean age, 63.92 ± 12 years (range 22-87); 57.4% male; 21.8% diabetic; 39.6% hypertensive; 87.1% had MDRD4 ≥ 60 ml/min/1.73 m (89.45 ± 14, range 62.36-134.14) and 12.9% had MDRD4 < 60 ml/min/1.73 m (45.38 ± 11, range 9.16-58.90)]. The most common indication for CT examinations was oncologic (81.2%). The only contrast agent administered was iopamidol; the mean dose was 107.83 ± 11 ml (range 70-140). The mean interval between pre-CT and post-CT laboratory tests was 4.06 ± 1 days. Only 13 patients received N-acetylcysteine; 9 of these had MDRD < 60 ml/min/1.73 m and 4 had MDRD4 ≥ 60 ml/min/1.73 m (p = 0.000).

Conclusions: The incidence of contrast-induced nephropathy was not significant in patients with glomerular filtration rates greater than 30 ml/min/1.73 m: these favorable results might be due to analyzing only scheduled examinations and to using relatively low doses of a "nonionic" iodinated contrast agent.