Final answer:
The glomerular filtration rate (GFR) is a critical measure of kidney function, often estimated by the creatinine clearance test, which uses a formula involving the patient's creatinine levels in the urine and plasma as well as urine flow rate over a 24-hour period, then adjusted for body surface area.
Step-by-step explanation:
Determining Glomerular Filtration Rate (GFR)
To assess renal function, one common measure is the glomerular filtration rate (GFR), which gives an indication of how well the kidneys are filtering blood. The creatinine clearance test is a practical method to estimate GFR. This test measures the amount of creatinine, a waste product from muscle metabolism, cleared from the blood by the kidneys.
The standard formula to calculate creatinine clearance (Ccr) requires the concentrations of creatinine in the urine (U) and plasma (B), and the urine flow rate (V), determined over a 24-hour period. The calculation is as follows:
UxV
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B
For accuracy, these results are often adjusted for body surface area (BSA) to a standard of ml/min/1.73 m². Other tests, such as the inulin clearance test and blood urea nitrogen (BUN) levels, can also provide insights into kidney function. However, due to the ease of measuring creatinine levels, it is more commonly used in clinical settings.