Renal function

Question 1

How would you calculate excretion rate

Answer 1

urine flow x [X]urine

Question 2

How would you calculate clearance of X

Answer 2

excretion rate of X / [X]plasma

Question 3

Filtration rate of X

Answer 3

[X]plasma x GFR

Question 4

What is clearance

Answer 4

Rate at which a specific solute disappears from the body via excretion or metabolism

Question 5

What is inulin

Answer 5

Polysaccharide isolated from plants

Inulin is neither reabsorbed nor secreted when passing through the kidney tubules

100% of inulin filtered is excreted

Question 6

What is creatinine

Answer 6

Breakdown product of phosphocreatine which is found in muscle

Produced at a constant rate by the body

Production and breakdown rates of phosphocreatine do not vary much

Used by clinicians to estimate GFR

Question 7

How can we calculate renal handling

Answer 7

Once we know GFR we can determine how the kidney handles any solute by measuring:
Solutes plasma concentration
Solutes excretion rate

By comparing filtered load of solute with its excretion rate, we can tell how the nephron handled that substance
If less substance appears in urine than was filtered then net reabsorption has occurred
If more substance appears in urine than was filtered then net secretion of the substance into the lumen has taken place

Question 8

What is Cockroft and Gault equation

Answer 8

[(140-age)x weight x constant] / serum creatinine