Radiocontrast Exposure Safe for Kidney Function

Robert Goulden, MBBS

Despite popular belief, radiocontrast has been deemed safe for long-term kidney function, according to new research.

A team, led by Robert Goulden, MBBS, Department of Epidemiology, Biostatistics and Occupational Health, Faculty of Medicine, McGill University, determined whether intravenous radiocontrast exposure is linked to clinically significant long-term kidney impairment. The researchers used a study design that permits stronger causal interpretation than existing observational research.

Common Belief

While it is widely believed radiocontrast is nephrotoxic, a number of recent observational studies found no evidence of an association between intravenous contrast and kidney injuries.

“Because these studies are at high risk of confounding and selection bias, alternative study designs are required to enable more robust evaluation of this association,” the authors wrote.

In the cohort study, the investigators examined all emergency department adult patients undergoing D-dimer testing between 2013-2018 in the Canadian province of Alberta.

Overall, there was 156,028 individuals who received a D-dimer test during the study period.

Fuzzy Regression

The team used a fuzzy regression discontinuity design exploiting the fact that individuals just either side of the eligibility cutoff for 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 researchers sought main outcomes of the estimated glomerular filtration rate (eGFR) up to 6 months following the index emergency department visit. The mean age of the patient population was 53 years old and the mean baseline eGFR level was 86 mL/min/1.73 m2.

At baseline, 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, there was a mean change in eGFR of -0.4 mL/min/1.73 m2 (95% CI, −4.9 to 4.0) associated with CTPA exposure.

“In this quasi-experimental cohort study of 156 028 individuals, exposure to intravenous contrast was associated with a 0.4 mL/min/1.73 m2 reduction in estimated glomerular filtration rate up to 6 months later, which was not statistically significant nor clinically meaningful,” the authors wrote.

Adverse Outcomes

Similarly, there was no evidence for an association with the need for kidney replacement therapy (risk difference [RD], 0.07%; 95% CI, −0.47% to 0.61%), mortality (RD, 0.3%; 95% CI, −2.9% to 3.2%), and acute kidney injury (RD, 4.3%; 95% CI, −2.7% to 12.9%), though the latter analysis was limited by missing data.

Subgroup analyses were potentially consistent with harm among patients with diabetes (mean eGFR change −6.4 mL/min/1.73 m2; 95% CI, −15.4 to 0.2).

However, this was not among those with other reported risk factors for contrast-induced nephropathy, but these analyses were relatively underpowered.

“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,” the authors wrote.

The study, “Association of Intravenous Radiocontrast With Kidney Function,” was published online in JAMA Internal Medicine.