Oh, Porphyria!

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 cuationary 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, randomised, phase 3, controlled, open-label, non-inferiority trial. Lancet 2017; 389(10,076):1312-1322.

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.