<unk>  <unk>  is a measure used in renal physiology to calculate renal<unk>  flow (RPF) and hence estimate renal function.
Where extraction ratio is the amount 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<unk>  is almost equal to RPF. Therefore, PAH clearance is a method to estimate renal<unk>  flow.
Effective renal plasma flow
Renal blood flow
Glomerular filtration rate
PAH clearance
Creatinine clearance
Renal protein reabsorption
Renal glucose reabsorption
Renal oligopeptide reabsorption