Are We Overly Concerned About Kidney Injury from Contrast-Enhanced Computed Tomography?

Information sourced from NEJM Journal Watch:

Are We Overly Concerned About Kidney Injury From Contrast-Enhanced Computed Tomography?

A Mayo Clinic study showed no excess risk associated with contrast.

The idea that intravenous contrast material is an important cause of acute kidney injury (AKI) is based largely on uncontrolled observations. A retrospective study challenges this conventional wisdom.

Mayo Clinic researchers identified all patients who had either contrast-enhanced or unenhanced chest, abdominal, or pelvic computed tomography (CT) scans during a 10-year period and for whom pre- and post-scan data on renal function were available. Propensity score matching was used to create 2 groups of 6000 patients each. One group had undergone contrast-enhanced CT, and the other had undergone unenhanced CT, but the groups were virtually identical in their distributions of baseline renal function and demographic and clinical variables that could predispose to kidney injury. Nearly all patients were inpatients.

Propensity-adjusted incidence of post-scan AKI (defined as an increase in serum creatinine level of ≥0.5 mg/dL during the 72 hours after scanning) was the same in the contrast-enhanced and unenhanced CT cohorts. Incidence of AKI ranged from 1% (in patients who had baseline estimated glomerular filtration rates [eGFRs] >90 mL/minute/1.73 m2) to 14% (in those who had baseline eGFRs <30 mL/min/1.73 m2), regardless of exposure to contrast.

COMMENT

This study suggests that intravenous contrast material is not responsible for most of the “bumps” in serum creatinine we see after contrast-enhanced computed tomography. Many factors other than exposure to contrast can explain fluctuating serum creatinine among sick inpatients. One limitation of the study is that it included too few patients with estimated GFRs <15 mL/minute/1.73 m2 to analyze a very low-GFR subgroup. Nevertheless, the findings suggest that when contrast is essential to maximize a CT scan's diagnostic yield, mild to moderate renal impairment should not preclude administration of intravenous contrast. Readers should be aware that University of Michigan researchers recently performed a similar study also using propensity score-matched controls (Radiology 2013; 267:94) [PubMed® abstract] and found that contrast was associated with greater risk for acute kidney injury; however, the absolute excess risk was small.

Allan S. Brett, MD reviewing McDonald JS et al. Radiology 2014 Apr.

CITATION(S):

McDonald JS et al. Risk of intravenous contrast material-mediated acute kidney injury: A propensity score-matched study stratified by baseline-estimated glomerular filtration rate. Radiology 2014 Apr; 271:65. [PubMed® abstract]

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