Biochemical Measurements Flashcards
(41 cards)
what are the two methods of testing glomerular function
glomerular filtration rate and proteinuria
what happens in the proximal tubule
sire of main reabsorption
what happens in the distal tubule
secretion
what happens in the loop of henle
concentration of filtrate
the perfect marker of GFR is inulin- why is it not used clinically
impracticable, not endogenous have to inject it
what is the urea cycle
the end of protein metabolism
how is urea transported
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)
what is urea
end product of protein metabolism in the liver
why is urea not as good at measuring GFR
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)
what produces creatine
muscle
what happens to creatinine in the body
renal excretion (90-95% filtered, 5-10% secreted by distal tubule)
is creatinine secreted into the renal tubule
yes (only downfall of it to measure GFR- but only 5-10%)
how do you assess GFR
eGFR (can also use creatinine or serum creatinine clearance)
what happens to serum creatinine as GFR decreases
it rises (not being filtered from blood)
what it then normal GFR value
above 120 mL/min
below what GFR does serum creatinine leave the reference interval
not until below 60 (not sensitive to changes in GFR until quite low)
what measure of creatinine is more sensitive to changes in GFR at values above 60
urine creatinine clearance
what affects serum creatinine
age (young higher) sex (males generally higher) muscle mass (more muscle higher) diet (poor= lower) ethnicity (higher if black)
what is eGFR (4 variable MDRD)
estimated GFR- adjusts serum creatinine for the confounding factors (age, sex, muscle mass)
what is serum creatinine clearance
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)
what are the CKD stages
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)
what is proteinuria a sign of
reduce glomerular function (plasma proteins shouldn’t be in urine)
how can you estimate proteinuria
24 hour urine collection
protein/creatinine ratio
proteinuria over what is suggestive is significant of glomerular damage
> 150 mg/day
