Does the current definition of contrast-induced acute kidney injury reflect a true clinical entity?

Abstract

Contrast-induced acute kidney injury (CI-AKI) is defined as either a 25% increase in or an absolute elevation in serum creatinine (SCr) of 0.5 mg/dL, 48 to 72 hours after parenteral contrast exposure. The objective of this study was to compare the incidence and complications of AKI between patients exposed and those unexposed to intravenous (IV) contrast. This was a retrospective cohort study using the electronic medical record of adult patients (>18 years) with and without contrast-enhanced abdominal or chest computed tomography (CT) between May 2008 and April 2009. Inclusion criteria were emergency department (ED) patients with normal renal function who received either a contrast-enhanced abdominal or a contrast-enhanced chest CT, compared to those unexposed to IV contrast, with a repeat SCr within 48 to 72 hours. Exclusion criteria were contrast exposure within 7 days before the index visit. CI-AKI in the contrast-exposed group and AKI in the contrast-unexposed group were defined by the same changes in SCr 48 to 72 hours after contrast or ED admission. Data were described by proportions or medians with 95% confidence intervals (CIs) or interquartile ranges (IQR; 25% to 75%). Group comparisons were by Mann-Whitney U or Fisher's exact test (α = 0.05, two tails). The contrast-exposed (n = 773) and contrast-unexposed (n = 2,956) patients were evenly matched for initial demographic, renal, and metabolic parameters. The incidence of CI-AKI/AKI was significantly higher for the patients unexposed versus exposed to contrast (8.96% vs. 5.69%, p = 0.003). There was no significant difference in mortality rates between contrast-exposed and unexposed patients (9.09% vs. 6.79%, p = 0.533). The definition of CI-AKI for ED patients with normal renal function may not represent a true clinical entity and the definition warrants revision.