3. Physiology
        3.2. Cardiovascular
            3.2.5. Special circulations
3.2.5.3. Renal

 

Renal circulation

Some kidney-specific figures

 

Renal blood flow

Renal blood flow

= 25% of cardiac output

= 1250mLs/min

Cortex vs medulla

 

Renal oxygen consumption

Renal oxygen consumption

= 7.2% of body oxygen consumption

= 18mLs O2/min

 

Oxygen extraction ratio

Oxygen extraction ratio
= 7.2%

This is coincidental because

Oxygen flux
= 250mLs O2
= body oxygen consumption

However,

Using slightly different numbers,

Blood flow is 24% of cardiac output
= 1200mL

Oxygen flux
= 240mL O2/min

Oxygen extraction ratio
= 18/240
= 7.5%

Measurement

Renal blood flow is measured using para-aminohippurate (PAH)

Equations

Renal plasma flow
= PAH uptake / [PAH] difference in renal arterial and venous blood

But because clearance is not 100%, therefore...

Effective plasma flow
= Urinary [PAH] x urine volume per unit time / venous [PAH]

Extraction of PAH is about 90%
--> Plasma flow x 0.9 = Effective plasma flow

Other notes

 

 

 

 

 

 

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