Progressive Care Nursing Certification (PCCN) Practice Exam

Which substance's clearance can indicate renal function?

1. Blood urea nitrogen (BUN)

2. Creatinine

3. Sodium retention

4. Protein levels

The correct answer is: Creatinine

The clearance of creatinine is a widely accepted indicator of renal function due to its constant production by muscle metabolism and its relatively stable serum levels in normal physiological conditions. Since creatinine is primarily filtered out of the blood by the kidneys, measuring its clearance can provide insight into how well the kidneys are functioning. The creatinine clearance test compares the creatinine level in a 24-hour urine sample against the serum creatinine level, allowing for an estimation of the glomerular filtration rate (GFR). A decrease in the clearance of creatinine indicates impaired kidney function, making it a reliable marker in evaluating renal health. In contrast, blood urea nitrogen (BUN) may reflect kidney function but can also be influenced by factors such as protein intake, hydration status, and liver function, which may make it less specific than creatinine. Sodium retention is a response observed in cases of reduced renal function, but it does not directly measure kidney performance. Protein levels can indicate certain kidney disorders but are not a direct measurement of renal function. Thus, utilizing creatinine clearance as a measure provides a clearer and more direct assessment of renal health.