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Contrast-Induced Nephropathy (CIN), also referred to as Contrast-Associated Acute Kidney Injury (CA-AKI) in modern terminology, is an acute decline in renal function following the administration of iodinated contrast media, particularly in CT imaging or angiography.

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It is a major consideration in at-risk populations and often prompts precautionary screening before contrast-enhanced imaging.

Pathophysiology

CIN results from a multifactorial injury:

1. Renal vasoconstriction: Reduced medullary blood flow, ischemia
2. Direct tubular toxicity: Primarily in the proximal tubules
3. Increased oxidative stress: ROS generation worsens ischemic injury

![Pathophysiological events and preventive strategies in contrast-induced acute kidney injury (CIAKI): Contrast agents damage several components of the kidney (blue boxes). Contrast medium toxicity induces membrane damage in epithelial and endothelial cells. Endothelial dysfunction and vasoactive substances released from epithelial cells cause vasoconstriction. Afferent arteriolar constriction results in a rapid decrease in glomerular filtration rate (GFR). The outer medulla is at risk of CIAKI owing to its high metabolic demand and comparatively low perfusion via the vasa recta. The latter constricts when exposed to contrast medium. Concomitant cell damage takes place owing to hypoxia, initiating apoptosis and aggravating renal hypoperfusion by cell oedema and further vasoconstriction. Concentration of contrast medium in the tubules and vasa recta increases fluid viscosity, which compromises urine and blood flow, thus decreasing GFR and oxygenation, and prolonging contrast medium exposure. Strategies for prevention of CIAKI such as fluid expansion and decreasing oxidative stress are based on pathophysiological knowledge (green boxes). NO, nitric oxide.

Fähling, M., Seeliger, E., Patzak, A. et al. Understanding and preventing contrast-induced acute kidney injury. Nat Rev Nephrol 13, 169–180 (2017). https://doi.org/10.1038/nrneph.2016.196](attachment:70122c26-f5cb-4b9c-b0a9-3931b51f902a:image.png)

Pathophysiological events and preventive strategies in contrast-induced acute kidney injury (CIAKI): Contrast agents damage several components of the kidney (blue boxes). Contrast medium toxicity induces membrane damage in epithelial and endothelial cells. Endothelial dysfunction and vasoactive substances released from epithelial cells cause vasoconstriction. Afferent arteriolar constriction results in a rapid decrease in glomerular filtration rate (GFR). The outer medulla is at risk of CIAKI owing to its high metabolic demand and comparatively low perfusion via the vasa recta. The latter constricts when exposed to contrast medium. Concomitant cell damage takes place owing to hypoxia, initiating apoptosis and aggravating renal hypoperfusion by cell oedema and further vasoconstriction. Concentration of contrast medium in the tubules and vasa recta increases fluid viscosity, which compromises urine and blood flow, thus decreasing GFR and oxygenation, and prolonging contrast medium exposure. Strategies for prevention of CIAKI such as fluid expansion and decreasing oxidative stress are based on pathophysiological knowledge (green boxes). NO, nitric oxide.

Fähling, M., Seeliger, E., Patzak, A. et al. Understanding and preventing contrast-induced acute kidney injury. Nat Rev Nephrol 13, 169–180 (2017). https://doi.org/10.1038/nrneph.2016.196

Risk Factors

Incidence

• General population: <2%
• High-risk groups (e.g., CKD + diabetes): up to 20–30%
• Significantly reduced with non-ionic, low- or iso-osmolar agents

Clinical Course

• Usually self-limiting: Creatinine peaks by day 3–5 and resolves within 1–2 weeks