biochemical measurements in renal disease

Question 1

what can glomeral function be divided into?

Answer 1

• GFR

- proteinuria

Question 2

what would be the ideal marker for GFR?

Answer 2

GFR would:

• appear at a constant rate
• freely filtered at the glomerulus
• not absorbed from the renal tubule
• not secreted into the renal tubule
• doesnt undergo extra renal elimination

Question 3

what are pros and cons of using inulin for clearance?

Answer 3

inulin clearance (best one?)

however not endogenous (so have to inject it and measure from blood and urine so impractical)

Question 4

pros and cons of using urea as a marker for GFR?

Answer 4

-using urea as a measurement for GFR will underestimate the GFR

Question 5

what is creatinine?

Answer 5

• a product of muscle metabolism

- people with larger muscle mass will secrete more creatinine

Question 6

what are the pros and cons of using creatinine as a marker for GFR?

Answer 6

-cons the creatinine isn’t sensitive to changes in GFR until the GFR is quite low

Question 7

what problem with using creatinine as a marker for GFR is this graph showing and what is the solution?

Answer 7

problem= creatinine isn’t sensitive to changes in GFR until the GFR is quite low

solution= urine creatinine clearance is sensitive to changes in GFR at these higher levels of GFR (60-120mL/min)

Question 8

what is urinary creatinine clearance?

Answer 8

-the volume of blood that is ‘cleared’ of creatinine per minute by glomerular filtration

Question 9

how is urinary creatinine clearance measured?

Answer 9

-creatinine is measured in blood and a 24 hour urine collection, and the volume of urine produced is also measured

The calculation is:
[urine creatinine conc x urine volume] / [ serum creatinine conc x duration of collection]

duration of the collection- measured in minutes!!

Question 10

what does serum creatinine reflect?

Answer 10

• kidney function (GFR)

- the amount of creatinine produced per day

Question 11

what affects the amount of creatinine produced per day?

Answer 11

• muscle mass
• diet
• age
• sex
• ethnicity

Question 12

what is the CKD stage for end stage renal failure?

Answer 12

CKD 5 (eGFR<15)

Question 13

what does a CKD of 4 suggest?

Answer 13

-patients that will need renal replacement treatment just depends when

Question 14

what is the problem with eGFR and what is measured if you need and accurate assessment of GFR?

Answer 14

• not very accurate at higher GFR (hence only report values <60)
• if its essential to get an accurate assessment of GFR you can use Cr-EDTA clearance

Question 15

what is proteinuria a marker for?

Answer 15

renal pathology

Question 16

are plasma proteins normally retained or excreted by the glomeruli?

Answer 16

-retained

Question 17

what suggests significant glomerular damage?

Answer 17

protein >150mg/day in the urine as usually plasma proteins are usually retained by glomeruli

Question 18

what is an issue with measuring protein in urine and what is the solution to this problem?

Answer 18

• urine can be more diluted

- can do a protein/creatinine ratio

Question 19

how would multiple myeloma and nephrotic syndrome present on a urine protein test?

Answer 19

-lots of protein in the urine

Question 20

what is proteinuria?

Answer 20

increased levels of protein in the urine

Question 21

what are the different types of proteinuria?

Answer 21

Question 22

what is microalbuminuria?

Answer 22

-refers to excretion of albumin in abnormal quantities but still below the limit of protein detection by dipstick

Question 23

what is the earliest manifestation of diabetic nephropathy?

Answer 23

-microalbuminuria

Question 24

what are some ways of expressing proteinuria?

Answer 24

• dipstick reading
• PCR (protein, creatinine ratio)
• total protein excretion
• ACR (albumin, creatinine ratio)

Question 25

what do the tubules allow the kidneys to of?

Answer 25

• glomerular filtration gets rid of waste

- tubules then reabsorb important substances such as water, electrolytes, amino acids, glucose ect

Question 26

summary slide xxx

Question 27

when is tubular function most useful?

Answer 27

-if it’s either exactly the same as or very different from serum osmolality