Manitoba Nephrology Nurse Practice Test

Which substance's clearance is often used to assess kidney function?

1. Urea

2. Creatinine

3. Glucose

4. Albumin

The correct answer is: Creatinine

Creatinine clearance is widely accepted as a standard test for evaluating kidney function. This is primarily due to creatinine being a byproduct of muscle metabolism that is produced at a relatively constant rate in individuals. The kidneys primarily excrete creatinine, and its clearance from the blood into the urine can provide an effective measure of glomerular filtration rate (GFR), an important indicator of renal function. The advantages of using creatinine for this purpose include its stability and the fact that it is not significantly reabsorbed or secreted by the renal tubules, making it a reliable indicator of kidney filtering capacity. Measurements of creatinine levels in both blood and urine allow for calculations that enable healthcare professionals to assess how well the kidneys are filtering waste products. While other substances such as urea, glucose, and albumin can provide information about kidney function and overall health, they do not serve as reliable indicators for GFR assessment. Urea clearance can be affected by other factors such as hydration status, and glucose is generally reabsorbed in healthy kidneys, with its presence in urine indicating a problem rather than serving as a marker of filtration. Albumin levels can indicate kidney damage or disease but do not provide a direct measure of kidney function in terms of clearance.