Contrast Nephropathy Is a Myth

Written by Alex Chen, MD

Be sure to read the counterpoint to this tomorrow, Contrast Nephropathy is Real, by Thomas Davis.

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There is increasing literature that supports the notion that radiocontrast administration does not increase the risk of developing acute kidney injury (AKI).

Why does this matter?
Contrast is often necessary to improve the diagnostic capabilities of our imaging. It is not uncommon to have to settle for sub-optimal, non-contrast imaging due to concern over causing contrast-induced nephropathy. The important question is: are we making these decisions with the best available evidence?  Is contrast causing AKI?

Ready-made diagnosis, “Just add contrast”
There is good reason for why contrast-induced nephropathy has occupied so much of our recent literature. As we utilize more CT imaging, we have to decide whether or not to add contrast on a regular basis. While earlier observational data has demonstrated that there is an increased risk of AKI after contrast administration, it has been plagued by a lack of control groups and the fact that contrast-induced nephropathy is meant to be a diagnosis of exclusion. No amount of statistical wizardry can account for all the confounders that exist, including the selection bias that goes on due to the fear of causing contrast-induced nephropathy in certain populations. More recent meta-analyses have demonstrated that there is no increased risk of AKI, need for renal replacement therapy, or increased mortality in patients that receive contrast compared to patients who do not. A recent study by Wilhelm-Leen et al., looked at approximately 6 million hospitalizations and did not show a statistically significant increased risk of AKI in patients receiving contrast compared to those who did not. They found, "the relation between radiocontrast administration and AKI is highly confounded, unpredictable, and sometimes bidirectional."  Meaning, in patients with fewer comorbidities IV contrast administration was actually "protective" for developing AKI.  More likely is the fact that sicker patients with more comorbidities are at increased risk of developing AKI regardless, and these are the patients who most often need contrasted studies.  There is association but not necessarily causation.  The Wilhelm-Leen analysis, with 6,000,000 patients, may be the most definitive study we will get.  A controlled trial would be unethical, as it would randomize some patients to receive suboptimal, non-contrast imaging.

Source
Contrast-associated acute kidney injury is a myth: Yes. Intensive Care Med. 2017 Dec 14. doi: 10.1007/s00134-017-4950-6. [Epub ahead of print]

Peer reviewed by Clay Smith, MD.

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