Renal clearance

Question 1

What is the equation for renal clearance?

Answer 1

C = (V x U) / P V = urine flow rate U = urine concentration P = plasma concentration

Question 2

Why is creatinine clearance as a measure of GFR less accurate in a renal disease patient with low GFR? Overestimation or underestimation?

Answer 2

1. Secreted component is a relatively larger fraction of the total excreted 2. More severe overestimation

Question 3

How do changes in GFR affect serum creatinine?

Answer 3

Less GFR = higher creatinine

Question 4

If serum creatinine is above normal is GFR above or below normal?

Answer 4

GFR would be low (below normal)

Question 5

What are the variables used to estimate GFR using the Cockcroft-Gault equation?

Answer 5

1. Blood levels of creatinine 2. Age 3. Lean body weight

Question 6

What are the variables used to estimate GFR using the MDRD study?

Answer 6

1. Serum creatinine 2. Age 3. African American yes/no 4. Gender