Biochemistry

Question 1

What criteria should a substance meet to be able to measure Glomerular Filtration rate (GFR)?

Answer 1

• Appear at a constant rate
• Be freely filtered at the glomerulus
• Not be reabsorbed from the renal tubule
• Not be secreted by the renal tubule
• Not undergo extra-renal elimination

Question 2

Why is Inulin not used to measure GFR if it fits all of the previous criteria?

Answer 2

It is not endogenous (produced by the body)
=> need to give it to the patient and then measure excretion

It is also NOT easy to measure in clinical practice

Question 3

Why is Urea not suitable for measuring GFR?

Answer 3

It doesnt appear at a constant rate
It is reabsorbed from the renal tubule
It undergoes extra-renal elimination

Question 4

Where is urea produced?

Answer 4

Liver => end product of protein breakdown

Question 5

Patients with a large muscle mass produce more Creatinine than those with a normal muscle mass. TURE/FALSE?

Answer 5

TRUE

Question 6

Why is creatinine not measured for GFR?

Answer 6

It is secreted into the renal tubule

Question 7

What is considered a normal GFR?

Answer 7

> 120mL/min

Question 8

If the GFR is very low, what happens to the serum creatinine?

Answer 8

It gets very high

Question 9

Give an example of creatinine measurement in a pre-dialysis patient?

Answer 9

600-700 micromol/L

Question 10

Why is creatinine not used as an indicator of GFR?

Answer 10

It is not sensitive to the small changes in GFR

Question 11

What 4 factors are used to give an estimated GFR (eGFR)?

Answer 11

Age
Sex
Ethnicity
Creatinine

Question 12

What is meant by urinary creatinine clearance?

Answer 12

volume of plasma that is cleared of creatinine per minute

Question 13

How do we calculate urinary creatinine clearance?

Answer 13

[creatinine]urine x urine volume
DIVIDED BY
[creatinine]serum x duration of collection

Question 14

What is urinary creatinine clearance used for?

Answer 14

It is sensitive to GFRs between 100-120mL/min

Question 15

When would 51Cr-EDTA clearance be used?

Answer 15

Before nephrotoxic agents are given in cancer patients

Question 16

CKD stage 5 indicates what?

Answer 16

End stage renal failure

Question 17

When is eGFR not completely accurate?

Answer 17

If it is >60

Question 18

How do we measure proteinuria?

Answer 18

24 hour urine collection

OR protein:creatinine ratio on a spot urine sample

Question 19

Protein over what level indicates significant glomerular damage?

Answer 19

> 150mg/day

Question 20

In Microalbuminuria, no protein is picked up on urine dipstick. TRUE/FALSE?

Answer 20

TRUE

Dipstick test is negative

Question 21

What does microalbuminuria indicate in certain patients?

Answer 21

earliest expression of diabetic nephropathy

Question 22

What treatment is given to slow the progression of diabetic nephropathy?

Answer 22

ACE inhibitor

Question 23

Overflow proteinuria occurs in what condition?

Answer 23

Multiple myeloma
B lymphocyte cancer
Causes plasma cells to make too many antibodies
=> too much protein for glomeruli to handle

Question 24

Why does nephrotic syndrome occur?

Answer 24

Less protein remains in the blood
=> oncotic pressure pushes fluid from blood to interstitial space
=> oedema occurs

Question 25

What is normally the cause of a pre-renal uraemia?

Answer 25

Blood loss

Question 26

What can cause a post-renal uraemia?

Answer 26

Stones/malignancy

Question 27

What causes are there for a renal uraemia?

Answer 27

Glomerulonephritis or Nephrotoxin

Question 28

If the urine and serum osmolality are close, this is a good sign. TRUE/FALSE?

Answer 28

FALSE

this means the glomeruli are having no effect on the fluid they are receiving from the blood serum