tests of renal function Flashcards
describe how concentrations of solute may change in a volume
input increases but excretion same = rise and vice versa
if volume increases concentration fall (water overload)
or water deprivation (rise in conc)
what are the three main functions of the renal system
excretion - urea, uric acid, creatinine
regulation - water, acid
endocrine - renin, epo, vit D
where do these excitable metabolite come from
urea
uric acid
creatinine
amino acid breakdown
purine break down
creatine breakdown in muscle
what three qualities of renal tests are needed
detect renal damage
monitor functional damage
distinguish between impairment and failure
what are the three places where kidney failure can occur
pre-renal - decreased ECFV or MI
renal - acute tubular necrosis
post renal - ureteral obstruction
what are the normal and altered levels of urine output
750-2000 mL / 24h
less than 400 = oliguria
less than 100 = anuria
polyuria is more than 3000
what are the normal and altered levels of plasma urea and what are the issues with this measurement
3-8 mmol/L
sensitive but not specific
increased in GI bleed, trauma, AKI, CKD
what causes renal hypo perfusion
more urea reabsorbed if tubular flow is slowed
MI
fluid loss
RA stenosis
what are the normal and altered levels of plasma creatinine
50-140 umol/L
as GFR decreases there is an increase in conc
it is not proportional to renal damage
what diseases cause increases in creatinine
jaundice
infection
diabetic ketoacidosis
people with higher muscle mass
what is used to measure GFR
DTPA
EDTA
what are the normal and altered levels of eGFR
90+ normal
60-90 - mild
30-59 moderately reduced function
15-29 severe
less than 15 or on dialysis = end stage
what is the reference range of creatinine clearance
100-130
usually 10 - 30% higher than GFR
how do levels of creatinine clearance change
increased in CKD
reduced by drugs such as salicylate or cimetidine
unreliable test
what are the normal and altered levels of urine sodium
around 20 mmol/L
increased due to diuretics, adrenal failure, high slat diet
deceased due to hyperaldosteronism, dehydration, CKD
