Extraction ratio
| Parameter | Value |
|---|---|
| renal blood flow | RBF=1000 ml/min |
| hematocrit | HCT=40% |
| renal plasma flow | RPF=600 ml/min |
| filtration fraction | FF=20% |
| glomerular filtration rate | GFR=120 ml/min |
| urine flow rate | V=1 mL/min |
| Sodium | Inulin | Creatinine | PAH |
|---|---|---|---|
| SNa=150 mEq/L | SIn=1 mg/mL | SCr=0.01 mg/ml | SPAH= |
| UNa=710 mEq/L | UIn=150 mg/mL | UCr=1.25 mg/mL | UPAH= |
| CNa=5 mL/min | CIn=150 ml/min | CCr=125 mL/min | CPAH=420 ml/min |
| ER=90% | |||
| ERPF=540 ml/min |
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.[1]
Measured in concentration in blood plasma, it may thus be expressed as:
, where Pa is the concentration in renal artery, and Pv is the concentration in the renal vein.
For instance, para aminohippuric acid (PAH) is almost completely excreted in the final urine, and thus almost none is found in the venous return (Pv ~0). Therefore, the extraction ration of PAH ~1. This is why PAH is used in PAH clearance to estimate renal plasma flow.
References
- ↑ Renal Mathematics Texas Tech University Health Sciences Center
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