S2.2 Measuremnt Of Kidney Funtion

Question 1

Kidney function is measure in terms of GFR, what is GFR?

Answer 1

The amount of filtrate produced from blood flow per unit time.

Question 2

What is the normal range for GFR?

Answer 2

Normal GFR is 90–120 mL/min /1.73m2

The normal total glomerular filtrate per day is 140 –180 L /day

Question 3

What factors can affect GFR?

Answer 3

Gender, age, size, pregnant

Question 4

What is compensatory hypertrophy?

Answer 4

Reduced nephron number, so existing nephrons get bigger
Healthy kidney can also get bigger
Nephrons end up working harder, so can wear out
Occurs mainly in childhood

Question 5

We cannot measure GFR, so we measure clearance, what is this?

Answer 5

The volume of plasma cleared of a substance per unit of time.

Renal Clearance = excretion rate / plasma concentration

Question 6

In order to measure clearance, what features must the substance have?

Answer 6

Be produced at a constant rate

Be freely filtered across glomerulus
Not be reabsorbed or secreted into the nephron

Question 7

What is the most accurate way to measure clearance?

Answer 7

Using inulin

Question 8

Why is measurement of clearance with inulin impractical?

Answer 8

Due to needing continuous IV or a catheter.

Question 9

What is 51-CR-EDTA?

Answer 9

Radio-active labelled marker used to measure clearance.

Used clinically in children or where indication of renal function required e.g. kidney transplant.

Question 10

What is creatinine?

Answer 10

Creatinine is the end product of muscle metabolism.

Therefore depends on age, diet and muscular build

Question 11

When is creatinine clearance used and how accurate is it?

Answer 11

Used in pregnancy

Overestimate (10%)

Question 12

What is the most common way to measure GFR?

Answer 12

Serum creatinine

Is more stable than creatinine in individuals

Question 13

What is eGFR?

Answer 13

How we measure GFR in hospitals.

However is inaccurate in those without kidney disease, kids, elderly, pregnancies