Contrast material-induced nephrotoxicity and intravenous low-osmolality iodinated contrast material

Abstract

Purpose: To determine whether intravenous low-osmolality iodinated contrast material is associated with post-computed tomography (CT) acute kidney injury (AKI).

Materials and methods: Institutional review board approval was obtained and patient consent waived for this HIPAA-compliant retrospective study. CT examinations performed over a 10-year period in adult inpatients with sufficient serum creatinine (SCr) data were identified. A one-to-one propensity-matched matched cohort analysis with multivariate analysis of effects was performed with post-CT AKI as the primary outcome measure (10,121 unenhanced and 10,121 intravenous contrast-enhanced CT examinations in 20,242 patients). Propensity matching was performed with respect to likelihood of patient receiving intravenous contrast material (36 tested covariates). The primary endpoint was post-CT AKI by using Acute Kidney Injury Network SCr criteria; the secondary endpoint was post-CT AKI by using traditional SCr criteria for contrast material-induced nephrotoxicity (CIN; SCr increase ≥0.5 mg/dL [44.20 μmol/L] or ≥25%). Multivariate subgroup threshold analysis was performed (SCr <1.5 [<132.60 μmol/L]; ≥1.5 to ≥2.0 mg/dL [≥132.60 to ≥176.80 μmol/L]) and adjusted for assigned propensity scores.

Results: Intravenous low-osmolality iodinated contrast material had a significant effect on the development of post-CT AKI for patients with pre-CT SCr levels of 1.6 mg/dL (141.44 μmol/L) or greater (odds ratio, 1.45; 95% confidence interval [CI]: 1.11, 1.89;P = .007). This effect strengthened as pre-CT SCr increased. Patients with stable SCr less than 1.5 mg/dL (132.60 μmol/L) were not at risk for developing CIN (P = .25, power > 95%). Both endpoints demonstrated similar results (eg, SCr ≥1.6 mg/dL [141.44 μmol/L] by using traditional CIN criteria: odds ratio, 1.64; 95% CI: 1.18, 2.28; P = .003). Post-CT AKI was prevalent in both the unenhanced and contrast-enhanced CT subgroups, and it increased with increases in pre-CT SCr. Many risk factors contributed to development of post-CT AKI, regardless of iodinated contrast material.

Conclusion: Intravenous low-osmolality iodinated contrast material is a nephrotoxic risk factor, but not in patients with a stable SCr level less than 1.5 mg/dL. Many factors other than contrast material can affect post-CT AKI rates.

Figure a:

To convert SCr levels to International System of Units (micromoles per liter), multiply by 88.4. (a) Graph shows odds ratios and 95% CIs for development of post-CT AKI (defined by AKIN SCr criteria; SCr increase by ≥0.3 mg/dL or ≥1.50 times above baseline) comparing contrast-enhanced CT to unenhanced CT in the propensity-score adjusted subgroup multivariate analyses, subdivided by common clinical serum creatinine thresholds. Values on x-axis are thresholds for SCr. For example, odds ratio and 95% CI for 1.7 mg/dL represents the results for subgroup of patients whose pre-CT SCr was 1.7 mg/dL or greater. (b) Graph shows odds ratios and 95% CIs for development of post-CT AKI (defined by traditional CIN SCr criteria; SCr increase by ≥0.5 mg/dL or ≥1.25 times above baseline) by comparing contrast-enhanced CT to unenhanced CT in the propensity-score adjusted subgroup multivariate analyses, subdivided by common clinical serum creatinine thresholds. Values on x-axis are thresholds for SCr. For example, odds ratio and 95% CI for 1.7 mg/dL represents results for subgroup of patients whose pre-CT SCr was ≥1.7 mg/dL.

Figure b:

To convert SCr levels to International System of Units (micromoles per liter), multiply by 88.4. (a) Graph shows odds ratios and 95% CIs for development of post-CT AKI (defined by AKIN SCr criteria; SCr increase by ≥0.3 mg/dL or ≥1.50 times above baseline) comparing contrast-enhanced CT to unenhanced CT in the propensity-score adjusted subgroup multivariate analyses, subdivided by common clinical serum creatinine thresholds. Values on x-axis are thresholds for SCr. For example, odds ratio and 95% CI for 1.7 mg/dL represents the results for subgroup of patients whose pre-CT SCr was 1.7 mg/dL or greater. (b) Graph shows odds ratios and 95% CIs for development of post-CT AKI (defined by traditional CIN SCr criteria; SCr increase by ≥0.5 mg/dL or ≥1.25 times above baseline) by comparing contrast-enhanced CT to unenhanced CT in the propensity-score adjusted subgroup multivariate analyses, subdivided by common clinical serum creatinine thresholds. Values on x-axis are thresholds for SCr. For example, odds ratio and 95% CI for 1.7 mg/dL represents results for subgroup of patients whose pre-CT SCr was ≥1.7 mg/dL.