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Post-contrast AKI (or contrast induced nephropathy as it used to be called) is one of those hot-button issues in modern medicine. Is it really a thing? Was it ever, really? Neda Frayha, MD sits down with Salim Rezaie, MD of Rebel EM for an invigorating conversation about this controversial topic and what the literature actually tells us about it. 

Pearls:

• The term contrast-induced nephropathy has fallen out of favor to post-contrast AKI because the debate about contrast’s role in kidney injury rages on.
• Much of the recent literature has not shown a difference in AKI for those who receive a CT with contrast.
• Earlier studies were based on contrasts of higher volume and osmolarity given arterially that are not routinely used today.
• Remember that studies excluded those who had a renal transplant, GFR<30-45 and Cr>4.

• Terminology: contrast-induced nephropathy has fallen out of favor to post-contrast AKI because we aren’t sure if contrast is really the culprit
• Issues with the literature:
• • Many studies involved high volume, high osmolar contrast given arterially, not venous, low volume or low osmolar contrast
  • • Early studies used 15,000 milliosmole contrast whereas today we are using 320-800 milliosmoles or even iso-osmolar contrast
    • Shown that route does make a difference. People receiving arterial contrast (ie: coronary angiography) are more at risk of AKI
  • Studies are observational so you cannot get to causation, just association
  • • Other potential risk factors: comorbid conditions (diabetes, heart failure, hypertension), volume depletion, concurrent medications (vancomycin, NSAIDs, diuretics)
  • Are outcomes clinical or patient-oriented (ie: dialysis, death, increased length of stay) or a lab value change?
• New literature:
• • 1. Annals of EM 2017 (Hinson et. al)
  • • Single center
    • Retrospective cohort study
    • 17,000 patients who underwent CT with contrast, without contrast or no CT at all
    • • Excluded if Cr > 4mg/dL or renal transplant
    • Bottomline: no difference in patient-oriented outcomes (dialysis, mortality)
  • 2. Annals of EM 2017 (Aycock et. al)
  • • Meta-analysis
    • 28 articles with 100,000 patients
    • Bottomline: no difference in patient-oriented outcomes (dialysis, mortality)
  • 3. Lancet 2017 (AMACING trial)
  • • Randomized control trial (three parallel group, open label, non-inferiority)
    • • Excluded if GFR<30 or had renal replacement or required some sort of emergency procedure
    • Bottomline: crystalloid or no crystalloid did not differ in preventing AKI
  • 4. Journal of Critical Care 2019
  • • Single center
    • Retrospective, propensity-matched patients with sepsis
    • Bottomline: no difference in rates of AKI
  • Recent radiology literature also supports no difference in AKI after CT with contrast
  • NEJM June 2019 article is more cautionary and generated a great deal of discussion challenging every one of its points

References:

1. ACR Manual on Contrast Media, Version 10.3. Published 2018. https://www.acr.org/-/media/ACR/files/clinical-resources/contrast_media.pdf 
2. Biondi-Zoccai G, Lotrionte M, et al. Nephropathy after administration of iso-osmolar and low-osmolar contrast media: Evidence from a network meta-analysis. International Journal of Cardiology 2014; 172(2):375-380.
3. Davenport MS, Khalatbari S, et al. Contrast material-induced nephrotoxicity and intravenous low-osmolality iodinated contrast material. Radiology 2013; 267(1):94-105.
4. Davenport MS, Khalatbari S, et al.Contrast material–induced nephrotoxicity and intravenous low-osmolality iodinated contrast material: risk stratification by using estimated glomerular filtration rate. Radiology 2013; 268(3):719-728. 
5. Ho YF, Hsieh KL, et al. Nephrotoxic polypharmacy and risk of contrast medium-induced nephropathy in hospitalized patients undergoing contrast-enhanced CT. American Journal of Roentgenology 2015; 205(4):703-708. 
6. Hinson JS, Ehmann MR, et al. Risk of acute kidney injury after intravenous contrast media administration. Ann Emerg Med 2017; 69(5):577-586.e4.
7. Kidney Disease Improving Global Outcomes (KDIGO) Clinical Practice Guideline for Acute Kidney Injury. Published 2012. https://kdigo.org/wp-content/uploads/2016/10/KDIGO-2012-AKI-Guideline-English.pdf 
8. McDonald JS, McDonald RJ, et al. Risk of intravenous contrast material–mediated acute kidney injury: a propensity score-matched study stratified by baseline-estimated glomerular filtration rate. Radiology 2014; 271(1):65-73.
9. McDonald JS, McDonald RJ, et al. Risk of acute kidney injury, dialysis, and mortality in patients with chronic kidney disease after intravenous contrast material exposure. Mayo Clinic Proceedings 2015; 90(8):1046-1053.
10. McDonald RJ, McDonald JS, et al. Intravenous contrast material exposure is not an independent risk factor for dialysis or mortality. Radiology 2014; 273(3): 714-725.
11. Nijssen EC, Rennenberg RJ, et al. Prophylactic hydration to protect renal function from intravascular iodinated contrast material in patients at high risk of contrast-induced nephropathy (AMACING): a prospective, randomized, phase 3, controlled, open-label, non-inferiority trial. Lancet 2017; 389(10,076):1312-1322.
12. Reed MR, Meier P, et al. The relative renal safety of iodixanol compared with low-osmolar contrast media: a meta-analysis of randomized controlled trials. JACC: Cardiovascular Interventions 2009; 2(11):1167.