Effective renal plasma flow
(eRPF) is a measure used in renal physiology
to calculate renal plasma flow
(RPF) and hence estimate renal function
Where extraction ratio 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 is a method to estimate renal plasma flow.