Which labs should be monitored to assess kidney function when using iodinated contrast media?

• A. Potassium and Sodium
• B. Serum creatinine and BUN
• C. Calcium and Magnesium
• D. ALT and AST

Answer: (B)

When iodinated contrast is used, the kidneys can be stressed, so you focus on labs that show how well the kidneys are filtering waste. Serum creatinine and BUN are the best choices because they directly reflect kidney function. Creatinine comes from muscle metabolism and is cleared by the kidneys; as the glomerular filtration rate drops, creatinine rises, indicating reduced filtration. BUN measures urea nitrogen cleared by the kidneys and can rise with decreased kidney function or dehydration, providing complementary information. Together, they give a clearer picture of whether kidney function is being affected by the contrast.

Baseline values are important, with follow-up typically about 24 to 48 hours after the procedure and sometimes up to 72 hours. A rise in creatinine (often defined clinically as about 0.5 mg/dL or a 25% increase from baseline) signals potential contrast-induced nephropathy and prompts closer management. Other labs listed, like electrolytes (potassium, sodium), minerals (calcium, magnesium), or liver enzymes (ALT, AST), aren’t specific measures of kidney filtration and aren’t the primary indicators used to monitor for contrast-related kidney effects.