A 70-year-old man with diabetic nephropathy (eGFR 25 mL/min/1.73m²) requires IV contrast-enhanced CT for staging of a newly diagnosed renal mass. Serum creatinine is 250 µmol/L. Which statement best reflects the risk-benefit consideration and recommended precaution for iodinated contrast administration in this patient?

• A Contrast can be given after IV hydration with isotonic saline pre- and post-procedure; metformin should be withheld ✓
• B Contrast is absolutely contraindicated; the scan should be performed without contrast
• C Contrast can be given without precaution as post-contrast AKI risk is overstated
• D Gadolinium-based contrast should be substituted for iodinated contrast

Explanation

Post-contrast acute kidney injury (PC-AKI) risk is elevated in patients with eGFR below 30 mL/min/1.73m². Current ESUR guidelines recommend IV hydration with isotonic saline (1 mL/kg/hr for 6-12 hours before and after contrast) to reduce nephrotoxicity risk. Metformin must be withheld at the time of contrast administration and for 48 hours afterwards due to the risk of lactic acidosis if AKI supervenes. Low-osmolar or iso-osmolar non-ionic contrast agents should be used at the lowest diagnostic dose. Contrast is not absolutely contraindicated when the clinical indication is strong; risk-benefit analysis guides the decision. Gadolinium is contraindicated in severe renal failure due to nephrogenic systemic fibrosis risk.

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

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