Definition

Contrast-induced nephropathy (CIN) is a controversial term typically used to define an AKI following contrast exposure. The definition is a 25% increase in serum creatinine or an absolute increase in serum creatinine of 0.3mg/dL following administration of iodinated radiocontrast. This should be a rule-out diagnosis after considering other causes. 

• Typically occurs approximately 24 to 48 hours (peaks at 3-5 days) after administration of contrast and is typically non-oliguric.
• CIN often resolves within 10 days.

Risk Factors

• CIN incidence varies from 0-21% and is dependent on patient comorbidity, procedure type, and route of contrast material. The risk of CIN is directly correlated to the stage of CKD with a 30% risk in patients with an eGFR <30. 
• Incidence is higher after procedures that involve intra-arterial injection and higher volumes of contrast. The presence of one or more of the following risk factors increases risk: 
  • Pre-existing chronic kidney disease (GFR <60 mL/min).
  • Age >75.
  • Hypovolemia.
  • Diabetes mellitus. 
  • Nephrotoxic medications. 
  • Sepsis.
  • Increased contrast volume (e.g., coronary catheterization with left ventriculogram).
• Online risk calculators are available for post-PCI risk https://www.mdcalc.com/mehran-score-post-pci-contrast-nephropathy  

Management 

Prevention:

• Ensure the patient has a stable Cr/eGFR prior to contrast exposure.
• Carefully consider the risks and benefits of contrast administration in patients at risk for CIN. Consider alternate imaging studies (e.g., contrast-enhanced ultrasound or magnetic resonance imaging with gadolinium), delaying study to allow time for Cr stabilization, and minimizing contrast volume. 
• If contrast exposure is unavoidable and patient has an eGFR <30 or multiple risk factors and eGFR <45, prophylactic fluids are recommended:
  • IV fluids: pre-hydration with isotonic fluid prevents nephropathy. In patients who cannot receive IV fluids (e.g., CHF), the conventional wisdom is to hold diuretics if possible. 
    • Give NS at 1-3mL/kg/hr (~100mL/hr) for 1-12 hours prior to procedure and 6-12 hours post. In patients who need a STAT scan, you can give them a fixed volume of 500 mL NS prior to the scan if they have no contraindications. Monitor volume status. 
• Sodium bicarbonate, N-acetylcysteine, or pre-treatment hemodialysis are not recommended for the prevention of contrast nephropathy.
• Discontinue potential nephrotoxic medications, including NSAIDs and diuretics prior to study. Hold metformin for at least 48 hours prior to contrast exposure if GFR <60.

Treatment is supportive, including dialysis if necessary. In most cases, the contrast nephropathy resolves within 1 week.

• In patients with ESRD on dialysis, hemodialysis should be done within 72 hours after the scan. 
• Avoid nephrotoxic medications, closely monitor electrolytes, fluid status and strict Ins and Outs.

Key Points

• Hydration and minimizing the amount of contrast are the only strategies that reduce CIN.
• Avoid nephrotoxic agents if possible. 
• Start IV hydration prophylaxis as soon as possible in patients without contraindications.
• Treatment is supportive and most cases should resolve within 10 days. 

Rudnick MR, Leonberg-Yoo AK, Litt HI, Cohen RM, Hilton S, Reese PP. The Controversy of Contrast-Induced Nephropathy with Intravenous Contrast: What Is the Risk? Am J Kidney Dis 2020;75:105-13. 10.1053/j.ajkd.2019.05.022

Shah R, Le FK, Labroo A, Khan MR. Contrast-associated acute kidney injury. Quant Imaging Med Surg. 2020;10(4):891‐894. doi:10.21037/qims.2020.03.2