Effective renal plasma flow (eRPF) is a measure used in renal physiology

Renal physiology

Renal physiology is the study of the physiology of the kidney. This encompasses all functions of the kidney, including reabsorption of glucose, amino acids, and other small molecules; regulation of sodium, potassium, and other electrolytes; regulation of fluid balance and blood pressure;...

 to calculate renal plasma flow (RPF) and hence estimate renal function

Renal function

Renal function, in nephrology, is an indication of the state of the kidney and its role in renal physiology. Glomerular filtration rate describes the flow rate of filtered fluid through the kidney...

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Where extraction ratio

Extraction ratio

Extraction ratio is a measure in renal physiology, primarily used to calculate renal plasma flow in order to evaluate renal function. It is the amount of compound entering the kidney that got excreted into the final urine....

 is the ratio of compound entering the kidney that got excreted into the final urine.

When using a compound with an extraction ratio near 1, such as para-aminohippurate (PAH), then eRPF is almost equal to RPF. Therefore, PAH clearance

PAH clearance

Para aminohippurate clearance or PAH clearance is a method used in renal physiology to measure renal plasma flow, which, in turn, is a measure of renal function....

 is a method to estimate renal plasma flow.