10. Renal clearance

Question 1

definition

Answer 1

volume of plasma from which the substance is completerly cleared per unit ( from renal)

Question 2

renal clerance - calculation

Answer 2

Cx = Ux . V / Px
Cx = clearance of x ( ml / min)
Ux = urine concentration of x ( mg / ml)
Px = plasma concentation of X ( mg / ml)
V = urine flow rate (ml/ min(

Question 3

if renal clearance equals / smaller than GFR

Answer 3

Cx smaller : if smaller net tubular reasbsorption of X
Cx bigger : net tubular secretion of X
Cx = GFR : no net secretion or reabsorpition

Question 4

Inulin clearance can be used to … ( why )

Answer 4

calculate GFR because it is freely filtered an is neithere reabsorder nor secreted

Question 5

What is clearance? With what unit of measurement is it expressed?

Answer 5

• The volume of plasma from which a substance is completely cleared per unit of time; measured in milliliters per minute (mL/min)

Question 6

• What is the formula for calculating the clearance of substance X, the volume of plasma cleared completely of X per unit of time?

Answer 6

Clearance of X = Urine concentration of X (mg/mL) × urine flow rate (mL/min) divided by plasma concentration of X (mg/mL) (Cx = Ux × V/Px)

Question 7

• If renal clearance is less than the glomerular filtration rate of substance X, there is net tubular ____ (reabsorption/secretion) of X.

Answer 7

Reabsorption

Question 8

• X is measured in a patient. Plasma level (Px) is 100 mg/mL, urine level (Ux) 200 mg/mL, urine flow (V) 1 mL/min. What is X’s clearance (Cx)?

Answer 8

Cx (mL/min) = (Ux × V)/Px = (200 mg/mL × 1 mL/min)/100 mg/mL = 2 mL/min

Question 9

• In a patient, Y’s clearance (Cy) is 3 mL/min. He voids 3 mL/min. Plasma level (Py) is 5 mg/mL. What is the urine level of substance (Uy)?

Answer 9

Knowing Cy = (Uy × V)/Py: Uy = (Cyy

Question 10

• If renal clearance is equal to the glomerular filtration rate of substance X, is there net tubular secretion or reabsorption of X?

Answer 10

Neither—because clearance is equal to glomerular filtration rate, there is neither net secretion nor net reabsorption