Renal Clearance = volume of plasma that would have to be fully cleared for the substance to account for the amount of substance appearing in the urine per minute
' measure of how efficient/effective the kidney is at removing a substance from the blood'

the substance enters the nephron from the afferent arteriole at a specific concentration
fluid is filtered in the glomerulus along with some of the substance
a different concentration of the substance leaves the glomerulus in the blood
some of the substance is reabsorbed
a different concentration of the substance leaves the kidney in the blood
the volume of the blood is cleared of the substance in accordance with its relative concentration

Clearance = (conc in urine x volume urine produced/minute) / conc in plasma

expressed as ml/min

-the value for GFR is the most important piece of information to diagnose kidney function

- GFR can be determined by measuring the clearance of Creatinine

Creatinine and GFR

creatinine is filtered as easily as water and isn't reabsorbed from tubules
plasma volume filtered per minute is completely cleared of creatinine
clearance value of creatinine = GFR

Inulin and GFR

Inulin clearance can be used as a measure of GFR
it's infused into the blood stream at a constant level
it isn't secreted or reabsorbed, so the amount passed in the urine should be the amount infused

Amount per minute in urine = amount filtered per minute

Comparing Clearance Ratios

The clearance of a substance can be compared with Inulin:

Clearance of X is lower than Inulin = X is not freely filtered or is reabsorbed (more retained in blood and not fully cleared)
Clearance of X is higher than Inulin = X is secreted (more taken from blood beyond filtration into tubular fluid) e.g. PAH

PAH

-the clearance of PAH (an organic acid) can be used to work out how much plasma is perfusing the kidney

-PAH is freely filtered, with the remainder being secreted into the proximal tubule

PAH in urine = PAH filtered + PAH secreted

- amount of PAH is equal to the amount of plasma flowing through the kidney

Filtration Fraction = fraction of the plasma perfusing the kidney that is filtered

= GFR/RPF

- normally 0.15-0.20

Filtered Load = the amount of a solute that is filtered in one minute given that the solute is freely filtered

-calculated from the GFR and plasma concentration of a solute

filtered load = GFR X Plasma concentration

	Created by Louise Mason about 7 years ago

Animal Disease 1 Veterinary Medicine Note on GFR, Renal Clearance and Autoregulation of Renal Blood Flow, created by Louise Mason on 08/03/2017.