A colleague recently told me that his hospital requires creatinine level results before a CT scan with contrast can be ordered. He said they also have to ask permission from the radiologist to give IV contrast before having the creatinine level results. There's a lot to unpack here, but it's clearly time to review contrast nephropathy.
Medical schools have drilled into students since the 1950s that IV contrast is dangerous and kills kidneys. To be fair, the contrast agent used then was harmful and patients did suffer renal injury due to a lack of guidelines. Since then, thousands of articles have been published on this, even though today's iodinated contrast agent has repeatedly been found safe compared with the agents previously used. Contrast nephropathy is a boogeyman that seems more and more like a strawman.
Prospective randomized controlled studies are lacking and will likely never be performed. (Imagine getting those past the IRB.) Numerous large and well-designed observational studies and meta-analyses, however, have confirmed that the risk of acute kidney injury (AKI) from contrast has been seriously overestimated for decades.
One systemic review and meta-analysis measured the incidence of AKI by creatinine level or estimated glomerular filtration rate (GFR) 48 to 72 hours after IV contrast in 25,950 patients. (Radiology. 2013;267:119.) Some of these studies were huge—one had more than 50,000 patients, and another meta-analysis had 107,335. (Radiology. 2013;267:106; Ann Emerg Med. 2018;71:44.)
All of these found that those who underwent CT with contrast were not found to have increased frequency of AKI up to six months after. (Ann Emerg Med. 2017;69:577.) Contrast has not been shown to be an independent risk factor for dialysis or mortality. (Radiology. 2014;273:714.) I don't have enough space to list all the studies finding no significant association between IV contrast and a rise in creatinine. (Invest Radiol. 2019;54:312.)
The risk of contrast nephropathy in patients with severe kidney disease is much lower than previously believed, with AKI estimates ranging from zero to two percent for GFRs of 30 to 44 and zero to 17 percent for GFRs under 30. One trial using renal biomarkers at four to six and 48 to 96 hours after contrast to measure kidney excretion found no difference in 511 patients with chronic kidney disease. (Eur Radiol. 2015;25:1926.) Patients on maintenance dialysis should be treated similarly to those not receiving renal replacement therapy. And patients on dialysis who receive IV contrast media also do not require alteration in the routine dialysis schedule, regardless of residual kidney function.
CT with IV contrast can provide timely information that changes clinical care in critically ill patients or those with a large burden of comorbidities. One retrospective study found no increased incidence of AKI in 1464 patients with sepsis who underwent CT with IV contrast. (J Crit Care. 2019;51:111.) The same was true of another retrospective study of 3848 oncology patients in the ICU. (AJR Am J Roentgenol. 2010 Aug;195(2):414.) And a systemic review and Bayesian meta-analysis of 560 critically ill patients again found no AKI. (Intensive Care Med. 2017;43:785.)
Eliminating creatinine screening has been shown not to result in higher rates of acute kidney injury or hemodialysis. (Am J Emerg Med. 2021 Jul;45:420.) With this much evidence, many of us should be asking why this is still a debate. Professional laziness is the answer. It is far easier to remember what we were taught in medical school than to challenge ourselves to connect the dots of what we observe each day in the ED.
This is another example of other specialties attempting to tell us how to practice, even with evidence to the contrary. This should be unacceptable to us, and we need to demand better for our patients. With all due respect to our radiology colleagues, they are not the primary physician caring for the patient at the bedside. Asking permission to perform a CT with contrast before a creatinine result is ludicrous. ED patients need imaging performed in a timely, accurate way, and contrast helps diagnose many conditions and can dramatically affect decision-making.
Thankfully, more and more societies are speaking out. The American College of Radiology, the National Kidney Foundation, and multiple emergency medicine committees agree that IV contrast media confers no measurable risk for AKI in patients with a baseline GFR of 45 or greater. Waiting for a creatinine to perform a CT scan with contrast is a waste of your time and your patient's time, and it doesn't make any sense. When a patient needs a contrast-enhanced CT scan, especially if it could change care, do not debate the risks and benefits of performing it. The question answers itself.
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Dr. Briggsis an assistant professor of emergency medicine at the University of Tennessee Medical Center in Knoxville. He is the founder, a podcast host, and the editor-in-chief of EM Board Bombs (https://www.emboardbombs.com), a multiplatform educational tool designed to provide board prep and focus on what EPs need to know for the practice of emergency medicine. Follow him on Twitter@blakebriggsmd.