The danger (?) of intravenous contrast media

Another study piling on the mounting evidence that at least modern contrast agents put into people’s veins (and not arteries) for CT scans might not be bad for your kidneys after all.

The biggest single center study of EM patients was just published in The Annals of Emergency Medicine, which studied 17,934 patient encounters and compared renal function across 7201 contrast-enhanced scans, 5499 non-con scans, and 5,234 folks with no-CT.

6.8%, 8.9%, and 8.1% were the rates of AKI respectively. As in, folks who received either no contrast or no CT imaging were more likely to have a significant rise in creatinine than people who got contrast. As in, contrast was protective (statistically). Using different cutoff guidelines for AKI, the three were all statistically equivalent.

Practice patterns here still get in the way. Patients with low GFRs are more likely to get fluids prior to receiving contrast, possibly explaining the pseudo-protective effect of contrast. Patients with poor renal function are less likely to get contrast in the first place, reducing the power for evaluating contrast’s effects on those with CKD. However, controlling for baseline GFR didn’t change the story: there wasn’t an increased risk associated with receiving intravenous contrast in this controlled retrospective study regardless of underlying renal disease.

Historically, randomized controlled trials designed to elucidate the true incidence of contrast-induced nephropathy have been perceived as unethical because of the presumption that contrast media administration is a direct cause of acute kidney injury. To date, all controlled studies of contrast-induced nephropathy have been observational, and conclusions from these studies are severely limited by selection bias associated with the clinical decision to administer contrast media.

Maybe with all this mounting evidence it’s time to do an RCT.

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