Which laboratory value is used to assess renal function in a neonate and would indicate dysfunction if elevated beyond 0.5 mg/dL?

Which laboratory value is used to assess renal function in a neonate and would indicate dysfunction if elevated beyond 0.5 mg/dL?

• A. Bilirubin level above 5 mg/dL
• B. Plasma creatinine exceeding 0.5 mg/dL
• C. Serum sodium above 150 mEq/L
• D. Magnesium level below 1.5 mg/dL

Answer: (B)

Renal function is best tracked by creatinine because it reflects glomerular filtration rate. Creatinine is produced at a relatively steady rate and cleared by the kidneys, so rising levels indicate reduced filtration and potential kidney dysfunction. In a neonate, a plasma creatinine level exceeding about 0.5 mg/dL suggests impaired renal clearance, signaling possible acute kidney injury or decreased GFR. Bilirubin measures liver clearance and hemolysis, not kidney function. Sodium elevation can reflect fluid balance or other issues but is not a direct marker of renal filtration. Magnesium levels relate to different metabolic or nutritional factors and don’t specifically indicate renal function.

Renal function is best tracked by creatinine because it reflects glomerular filtration rate. Creatinine is produced at a relatively steady rate and cleared by the kidneys, so rising levels indicate reduced filtration and potential kidney dysfunction. In a neonate, a plasma creatinine level exceeding about 0.5 mg/dL suggests impaired renal clearance, signaling possible acute kidney injury or decreased GFR.

Bilirubin measures liver clearance and hemolysis, not kidney function. Sodium elevation can reflect fluid balance or other issues but is not a direct marker of renal filtration. Magnesium levels relate to different metabolic or nutritional factors and don’t specifically indicate renal function.