Which test is most important to assess kidney function before administering iodinated contrast media?

• A. Serum electrolytes
• B. Liver function tests
• C. Blood urea nitrogen
• D. Serum creatinine

Answer: (D)

Assessing kidney function to predict how well the kidneys will clear iodinated contrast is focused on filtration capacity. Serum creatinine is the best single test for this because it directly reflects how well the kidneys are filtering. Creatinine is produced at a steady rate and is cleared by the kidneys; when kidney function drops, creatinine rises and the estimated glomerular filtration rate (eGFR) falls, signaling greater risk for contrast-related kidney injury. Blood urea nitrogen can be influenced by hydration, protein intake, and other factors, so it’s less specific for filtration. Electrolytes and liver function tests don’t directly measure renal clearance. Therefore, a baseline serum creatinine (and eGFR) provides the most reliable assessment of renal function before administering contrast.