Biochemistry

Question 1

What are the properties of the ideal GFR marker?

Answer 1

Freely filtered
Not reabsorbed or secreted
Be easy to measure
Not undergo extra-renal elimination

Question 2

Why is serum creatinine a less useful measure of kidney function than eGFR?

Answer 2

Patients may have a “normal” creatinine despite a large decrease in GFR: e.g. old women with low muscle mass/creatinine to begin with. A large fall in GFR may only appear as a slight increase in serum creatinine

Question 3

Which four variables does the MDRD equation for estimating GFR account for?

Answer 3

Serum creatinine, age, gender and race (black/non-black)

Question 4

What is the main drawback of the 4-variable MDRD eGFR equation?

Answer 4

Unreliable above 60mls/min

Question 5

Which assay is used when it is necessary to get a fully accurate assessment of GFR?

Answer 5

51-Cr-EDTA clearance

Question 6

What is “normal” protein excretion?

Answer 6

<150mg/day

Question 7

How can proteinuria be estimated/quantified?

Answer 7

24-hour urine collection

Spot protein/albumin:creatinine ratio helpful

Question 8

What is the earliest indication of diabetic nephropathy?

Answer 8

Microalbuminuria

Question 9

How can tubular function in an oliguric patient be assessed?

Answer 9

Urine:serum osmolality (in renal damage: 1.5:1)

Question 10

Give an example of a pre-renal, renal and post-renal cause of oliguria.

Answer 10

a) reduced perfusion e.g. hypovolaemia
b) intrinsic tissue damage e.g. glomerulonephritis
c) ureteric/urethric stone