A patient with eGFR 28 mL/min/1.73m² (CKD stage 4) requires urgent contrast-enhanced CT for suspected PE. The iodinated contrast agent required for CTPA poses the risk of contrast-induced nephropathy (CIN). Which preventive measure has the STRONGEST evidence for reducing CIN in high-risk patients?

• A N-acetylcysteine (NAC) 600 mg orally 12 hours before
• B Sodium bicarbonate infusion alone
• C Forced diuresis with furosemide prior to contrast administration
• D Intravenous isotonic saline (0.9% NaCl) hydration pre- and post-procedure ✓

Explanation

IV hydration with isotonic saline (0.9% NaCl or isotonic sodium bicarbonate) is the single intervention with the strongest evidence base for reducing contrast-induced acute kidney injury (CI-AKI). Adequate hydration maintains renal tubular flow and dilutes the nephrotoxic contrast. NAC (N-acetylcysteine) showed initial promise but multiple large RCTs (PRESERVE, ACT trials) showed no benefit over IV saline. Forced diuresis with furosemide is contraindicated (worsens dehydration). Iso-osmolar contrast agents and minimal volumes are also recommended.

Reference: Grainger & Allison's Diagnostic Radiology, 7th ed.

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