Biochemical Measurements

Question 1

what are the two methods of testing glomerular function

Answer 1

glomerular filtration rate and proteinuria

Question 2

what happens in the proximal tubule

Answer 2

sire of main reabsorption

Question 3

what happens in the distal tubule

Answer 3

secretion

Question 4

what happens in the loop of henle

Answer 4

concentration of filtrate

Question 5

the perfect marker of GFR is inulin- why is it not used clinically

Answer 5

impracticable, not endogenous have to inject it

Question 6

what is the urea cycle

Answer 6

the end of protein metabolism

Question 7

how is urea transported

Answer 7

from gut to liver in portal system
leaves liver and goes into systemic circulation where most excrete but 25% goes back into go (extra renal elimination, limits its value for measuring GFR)

Question 8

what is urea

Answer 8

end product of protein metabolism in the liver

Question 9

why is urea not as good at measuring GFR

Answer 9

extra renal elimination 
dietary dependent (doesnt appear at a constant rate)
is reabsorbed in the renal tubule (e.g urea in blood will increase if you loose  lot of blood/ water as filtration rate goes down)

Question 10

what produces creatine

Answer 10

muscle

Question 11

what happens to creatinine in the body

Answer 11

renal excretion (90-95% filtered, 5-10% secreted by distal tubule)

Question 12

is creatinine secreted into the renal tubule

Answer 12

yes (only downfall of it to measure GFR- but only 5-10%)

Question 13

how do you assess GFR

Answer 13

eGFR (can also use creatinine or serum creatinine clearance)

Question 14

what happens to serum creatinine as GFR decreases

Answer 14

it rises (not being filtered from blood)

Question 15

what it then normal GFR value

Answer 15

above 120 mL/min

Question 16

below what GFR does serum creatinine leave the reference interval

Answer 16

not until below 60 (not sensitive to changes in GFR until quite low)

Question 17

what measure of creatinine is more sensitive to changes in GFR at values above 60

Answer 17

urine creatinine clearance

Question 18

what affects serum creatinine

Answer 18

age (young higher) 
sex (males generally higher)
muscle mass (more muscle higher)
diet (poor= lower)
ethnicity (higher if black)

Question 19

what is eGFR (4 variable MDRD)

Answer 19

estimated GFR- adjusts serum creatinine for the confounding factors (age, sex, muscle mass)

Question 20

what is serum creatinine clearance

Answer 20

represents volume of plasma that is theoretically cleared of a substance per minute

(urine creatine conc x urine volume) / (serum creatine conc x duration of collection)

(can have high creatinine but be healthy as you making and excreting lots)

Question 21

what are the CKD stages

Answer 21

1= kidney damage with normal/ ^ GFR (GFR>/= 90)
2= kidney damage with mildly decreased GFR (60-89)
3= moderatly decreased GFR (30-59)
4=severely decreased GFR (15-29)
5 kidney failure (<15/ dialysis)

Question 22

what is proteinuria a sign of

Answer 22

reduce glomerular function (plasma proteins shouldn’t be in urine)

Question 23

how can you estimate proteinuria

Answer 23

24 hour urine collection

protein/creatinine ratio

Question 24

proteinuria over what is suggestive is significant of glomerular damage

Answer 24

> 150 mg/day

Question 25

what type of proteinuria is multiple myeloma

Answer 25

overflow (cancer of plasma cells (b lymphocyte that produces immunoglobulins) causes overproduction of the Ig= too much protein, kidney unable to filter it all)

Question 26

what type of proteinuria is albuminuria

Answer 26

glomerular (glomeruli not working as effective filter, abnormal proteins in urine. loose proteins (albumin) in urine which reduces oncotic pressure in capillaries so fluid moves into the interstitial fluid)

Question 27

what creates oncotic pressure

Answer 27

albumin

Question 28

what is anasarca

Answer 28

gross oedema

Question 29

what is microalbuminuria

Answer 29

excretion of albumin in abnormal quantities, below the limit to be detected by a dipstick

Question 30

what are the normal albumin creatine ratio figures

Answer 30

<2.5 males

<3.4 females

Question 31

what is the earliest expression of diabetic nephropathy

Answer 31

microalbuminuria

Question 32

what cant help stop progression of diabetic nephropahty

Answer 32

ace inhibitor

Question 33

what is tubular function

Answer 33

the reabsorbtion of important substances (water, electrolytes, amino acids, glucose) from the filtrate

Question 34

what are the pre renal causes of oliguria

Answer 34

reduced renal perfusion (blood loss)

Question 35

what are the post renal causes of oliguria

Answer 35

ureteric/uretheral obstruction (stones/malignancy)

Question 36

what are the renal causes of oliguria

Answer 36

intrinsic kidney tissue damage (glomerulonephritis, nephrotoxins)

Question 37

what is uremia

Answer 37

high levels of urea in the blood

Question 38

what happens to the components of urine when renal tubules stop working

Answer 38

increased urine sodium
decreased urine/serum urea (urine should always be much higher than serum)
urine/serum osmolality almost 1:1

Question 39

how does urine:serum osmolality show tubular function

Answer 39

urine osmolality should be much higher than serum

if ratio is close to one the tubules not filtering effectively as both liquids similar osmolality

Question 40

what is the commonest cause of proteinuria

Answer 40

glomerular (e.g. albuminuria, microalbuminuria)

Question 41

what is the best method for measuring tubular function

Answer 41

urine:serum osmolality