Mean creatinine decrease after administration of intravenous contrast in patients with renal dysfunction: implications for assessment of post-contrast nephrotoxicity.

BackgroundContrast nephropathy risk is traditionally assessed by the proportion of patients whose post-contrast serum creatinine (SCr) increases exceed certain thresholds. However, this method can be misleading because of random threshold selections, overlooking post-contrast creatinine decreases, and discarding continuous renal function data. The main impact of contrast on renal function can be revealed by analyzing the mean changes in SCr and evaluating their significance.PurposeTo analyze published data permitting calculation of mean SCr changes after intravenous contrast.Material and MethodsWe identified publications including patients with pre-existing renal dysfunction who received modern contrast agents, specified contrast type and dose, and means and standard deviations of SCr measurements before and after contrast.ResultsIn 14 articles, including 2057 patients, mean SCr pre-contrast was 148.6 µmol/L (1.68 mg/dL); decreasing significantly to 144.1 µmol/L (1.63 mg/dL) after contrast. Significant diminutions occurred at post-contrast intervals of 4, 7, and 10 days, and in patients who received hydration therapy. Of the patients, 6.6% met the specific thresholds for contrast nephropathy as defined by individual studies.ConclusionThe slight significant improvement in SCr after iodinated contrast suggests that some prior estimates of the risk of contrast-induced acute kidney injury (AKI) have been erroneously high and corroborates the current view that the risk of clinically important AKI after contrast is unlikely in patients with moderate renal failure. Threshold-based investigations of nephropathy may be misleading. Mean post-contrast SCr decline should be considered for clinical decisions regarding contrast administration. Future studies on the renal effects of contrast should analyze means, variation, and significance of post-contrast SCr changes.