S2 L3 Measurement of Kidney Function

Question 1

GFR and the individual

- GFR depends on?

Answer 1

• Age
• Gender
• Size of individual
• Size of kidneys
• Pregnancy

Question 2

Age:
- Babies:
Premature babies (affect on nephrons), GFR at birth? When does it become normal?
- Advancing age: When does GFR start declining? Why?

Answer 2

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Question 3

GFR in pregnancy:

• Increase in how much?
• What happens to size of kidney? Why?
• When does GFR return to normal?

Answer 3

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Question 4

GFR and disease?

• Reduction in GFR means…
• Why does GFR decrease?
• Increase in GFR means?
• If kidney function declines slowly…

Answer 4

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Question 5

What is the best substance to measure GFR?

• If used to measure kidney clearance a substance should…
• If all of these are true (listed in above Q), what equation is true?
• What actually is inulin?
• Why don’t we use inulin?

Answer 5

Don’t use inulin, because:
- It requires continuous IVI to
maintain steady state
- Requires catheter and timed urine collection

It isn’t practical on a large scale in NHS

Question 6

What other substance can be used? (still not on a big scale in the NHS)

• Why not used in big scale?
• When is it used?
• Why is it not completely accurate?

Answer 6

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Question 7

What substance is usually used in practice?

• Why is it used?
• Which properties allow it to be used?
• Why is it inaccurate (compared to inulin)
• How can it be measured?
• Disadvantages of it?

Answer 7

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Question 8

How is serum creatinine measured in USA and UK?
(units measured differently)
- Normal range of serum creatinine (have an idea of this)

Answer 8

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Question 9

What ‘things’ affect creatinine levels in an individual?

Answer 9

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Question 10

Factors that…

• increase serum creatinine
• reduce serum creatinine

Answer 10

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Question 11

Serum creatinine - Variations in GFR

• Talk about normal range - is it always healthy?
• If two individuals have the same serum creatinine in normal range, is this healthy for both of them?

Answer 11

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Question 12

Relationship between serum creatinine and measured GFR?

- Describe this relationship, is it linear, exponential?

Answer 12

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Question 13

Estimation of GFR from serum creatinine

• What is eGFR?
• Why ‘e’ infront of GFR?

Answer 13

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Question 14

What are:

• MDRD
• CKD-EPI

Answer 14

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Question 15

Problems with estimating GFR?

- What is the best way to work out if a patients GFR is normal?

Answer 15

Look at the CHANGE in serum creatinine or eGFR. As what is normal for one individual according to a range, may be too low or too high for a different individual