Biochemical Measurements Flashcards
name two ways of expressing glomerular function
glomerular filtration rate
proteinuria
what is the single best global marker of kidney function?
GFR
what marker is ideal for GFR but not used due to clinical difficulties?
inulin
too hard to measure
why is urea not commonly used as a marker for GFR?
not present at a constant rate
reabsorbed - would underestimate GFR
what does a high urea in the blood suggest?
poor kidney function, as it should be excreted in the urine rather than reabsorbed
what is the most commonly used marker for GFR?
creatinine
usually as urine creatinine clearance
when is serum creatinine sensitive to changes in GFR?
only when GFR is quite low
what is sensitive for changes in GFR at higher levels?
urine creatinine clearance
what is urinary creatinine clearance?
the volume of blood that is cleared of creatinine per minute by glomerular filtration
what three things need to be measured to calculated urinary creatinine clearance?
serum creatinine
urine creatinine
volume of urine
what is the calculation for the urinary creatinine clearance?
[creatinine]urine x urine volume
OVER
[creatinine]serum x duration of collection
what does a high urinary creatinine clearance suggest in terms of GFR?
higher GFR
shows that more clearance has occurred and that the kidneys are working well
what is eGFR?
estimated GFR
what can lead to proteinuria?
the glomeruli can be leaky in disease and let proteins through
how can the amount of protein in urine be estimated?
by doing a 24 hour collection
what does the protein/creatinine ratio provide information on?
how concentrated or dilute someone’s urine is
what protein level in the urine suggests significant glomerular damage?
> 150mg/day
name two types of proteinuria
overflow
glomerular
name a disease that causes overflow proteinuria
multiple myeloma
what happens in overflow proteinuria?
there is a gross overproduction of protein that overwhelms the glomeruli
what happens in glomerular proteinuria?
pathology stops the glomeruli from working properly
name a disease that cause glomerular proteinuria
nephrotic syndrome
what does PCR stand for?
protein creatinine ratio
what does ACR stand for?
albumin creatinine ratio
what does microalbuminuria refer ro?
the excretion of albumin in abnormal quantities, but still below the limit of detection by a dipstick
what is the earliest expression of diabetic nephropathy?
microalbuminuria
if a diabetic patient has microalbuminuria, what should be prescribed?
an ACE inhibitor
how do you assess tubular function?
measure serum and urine osmolalities
what will be serum and urine osmolalities be like if the tubules are functioning?
values will be very different between the two
