Intravenous Radio-contrast Does Not Harm Kidney Function: JAMA

Radiocontrast has long been thought of as nephrotoxic; however, a number of recent observational studies found no evidence of an association between intravenous contrast and kidney injury. Because these studies are at high risk of confounding and selection bias, alternative study designs are required to enable a more robust evaluation of this association. Therefore, researchers of Canada conducted a study to determine whether intravenous radiocontrast exposure is associated with clinically significant long-term kidney impairment, using a study design that permits stronger causal interpretation than existing observational research.

In this cohort study, researchers included 156 028 patients of emergency department who have undergone D-dimer testing between 2013 and 2018 in the Canadian province of Alberta. They used a fuzzy regression discontinuity design exploiting the fact that individuals just either side of the eligibility cutoff for a computed tomographic pulmonary angiogram (CTPA)—typically 500 ng/mL—have markedly different probabilities of contrast exposure, but should otherwise be similar to potential confounders. The major outcome assessed was estimated glomerular filtration rate (eGFR) up to 6 months following the index emergency department visit.

Key findings of the study were:

• At baseline, the researchers observed that the patients just above and below the CTPA eligibility cutoff were similar in terms of measured confounders and there was no evidence for an association of contrast with eGFR up to 6 months later.
• Overall, the mean change in eGFR of −0.4 mL/min/1.73 m2 associated with CTPA exposure.
• Similarly, they found no evidence for an association with the need for kidney replacement therapy (risk difference [RD], 0.07%), mortality (RD, 0.3%), and acute kidney injury (RD, 4.3%), though the latter analysis was limited by missing data.
• They noted that the subgroup analyses were potentially consistent with harm among patients with diabetes (mean eGFR change −6.4 mL/min/1.73 m2), but not among those with other reported risk factors for contrast-induced nephropathy. However, they mentioned that these analyses were relatively underpowered.

The authors concluded, "Using a cohort study design and analysis that permits stronger causal interpretation than existing observational research, we found no evidence for a harmful effect on kidney function of intravenous contrast administered for CTPA in an emergency setting."

For further information:

https://jamanetwork.com/journals/jamainternalmedicine/fullarticle/2778363