7.1. Renal Assessment and Micturition - Measurement of Glomerular Filtration Rate

Question 1

What is the equation for calculating GFR using insulin?

Note - A radioactive isotope (51Cr-EDta) was the used

Answer 1

Plasma Clearance of X = (Urine concentration of Insulin x Urine Flow Rate) / Plasma concentration of Insulin

Question 2

Is GFR measured often? Why?

Answer 2

No, it is too complex/impractical to measure

Question 3

What is used to estimate GFR?

Answer 3

Creatinine clearance

Question 4

Is creatinine endogenous or exogenous?

Answer 4

Endogenous

Question 5

What is GFR related to?

Answer 5

Plasma clearance of Creatinine

Question 6

What is Plasma Clearance of Creatinine equal to?

Answer 6

(Urine concentration of Creatinine x Urine Flow Rate) / Plasma concentration of Creatinine

Question 7

What can be determined from the relationship between GFR and Plasma Clearance of Creatinine?

Answer 7

GFR is directly proportional to 1 / (plasma concentration of Creatinine)
So Plasma Concentration of Creatinine, can be used to estimate GFR

Question 8

What can be determined from the relationship between GFR and Plasma Clearance of Creatinine?

Answer 8

GFR is directly proportional to 1 / (plasma concentration of Creatinine)
So Plasma Concentration of Creatinine, can be used to estimate GFR

Question 9

What are factors which will effect the serum creatinine?

Answer 9

1. Muscle Mass - there is more creatinine in athletes vs the malnourished
2. Dietary Intake - there is more creatinine in meat eaters vs vegetarians
3. Drugs - some lead to spurious increases (as does ketoacidosis)

Question 10

What is normal GFR?

Answer 10

100mls/min/1.73m^2

Question 11

What is the normal GFR concordant with?

Answer 11

1. A rnage of adults
2. Both sexes
3. kidney function and size

Question 12

How is kidney function expressed in relation to GFR?

Answer 12

This is expressed as a percentage of normal