Contrast-Associated Acute Kidney Injury

Contrast-associated acute kidney injury (CA-AKI) means that AKI occurs after exposure to iodinated contrast; the timing creates an association, not proof that contrast caused the renal injury. Contrast-induced acute kidney injury (CI-AKI) is the narrower diagnosis used when contrast is judged to be causal. The older label “contrast-induced nephropathy” assumes causation and is no longer the preferred term. AKI is diagnosed using standard criteria: - A serum creatinine increase of at least 27 µmol/L (26.5 micromol/L) within 48 hours - A serum creatinine increase to at least 1.5 times a known or presumed baseline within the previous 7 days - Urine output below 0.5 mL/kg/h for 6 hours A creatinine rise after contrast therefore requires clinical interpretation. The patient may have developed hypovolaemia, sepsis, hypotension, obstruction, or medication-related kidney injury at the same time. Calling every post-contrast creatinine rise “contrast-induced” can cause clinicians to miss the reversible cause that actually needs treatment. Proposed mechanisms of true contrast injury include renal medullary vasoconstriction with outer-medullary hypoxia, direct tubular epithelial toxicity, oxidative free-radical injury, and increased contrast viscosity that reduces medullary blood...