labs Flashcards
produced as the result of normal muscle metabolism? what is the breakdown from?
creatinine– production & excretion are constant/regular
breakdown of phosphocreatine
used to approximate the GFR? what is the normal level
creatinine– normal is 0.5-1.5 mg/dL
relationship between GFR & serum creatinine
inverse! 2x increase in Cr= 50% decrease in GFR so mild elevation= significant dysfunction even if its in the normal range
what is CrCl
- measure of the GFR
- normal is 100ml/min; dependent on age and gender (m>f)
how is CrCl measured directly?
24 hour urine collection– time consuming & hard for patients; both serum & urine needed; dispose of the first urine
- does NOT give a more accurate estimate than the prediction equations
how is CrCl measured indirectly
cockcroft-gault equation– age, kg, sex & serum cr are used in it
- used as the standard for drug dosing
sum filtraion of all functioning nephrons; gold standard for measuring kidney function? what is normal value?
GFR– varies by age, gender & body size
normal is above 90
5 uses of GFR
- identify kidney dz
- select doses
- avoid certain meds
- monitor CKD
- criteria for referral & dialysis
produced in liver, found in blood & secreted and reabsorbed by the kidneys; directly related to metabolic liver function; assuming normal liver, it is estimate of renal function
BUN– also affected by protein breakdown, hydration status, liver failure; rises faster than Cr with dehydration
how does serum Cr, eGFR, CrCl, BUN change when kidney is going bad?
Decreases– eGFR & CrCl
increase– serum Cr, BUN
symptomatic azotemia– N/V, lethargy
uremia
what is the diff. btwn acute and chronic kidney failure
time— 3 months
good screening test for obstruction & differentiation btwn acute & chronic renal dz
renal US
size difference btwn small & large kidneys
small < 10 cm; chronic dz
large > 12 cm; acute (potentially reversible; associated w/ DM, amyloid, infiltrative CA)
5 tests that can help in finding the cause of kidney failure
BUN:Cr
Urine NA
fractional excretion Na
urine Sp Gr
urine osmolality
in presence of kidney disease, what does BUN/Cr of over 20 mean?
pre-renal: GI bleed, less volume
Urine obstruction
in presence of kidney disease, what does BUN/Cr of under 20 mean?
intrarenal
often Chronic (CKD)
random urine Na of what value suggests dehydration? what value sugguests kidney/adrenal disease?
- Na under 10 suggests dehydration– CHF, liver dz
- Na over 20 suggests kidney/adrenal dsease
- electrolytes can be used to calculate FENa
helpful to distinguish btwn pre-renal and intrarenal azotemia; over 1% means intra-renal azotemia while under 1% means pre-renal azotemia
FENa (fractional excretion of Na)
prerenal vs intrarenal vs postrenal
- urine Na under 10
- serum BUN:Cr over 20
- FENa under 1%
- Sp Gr over 1.020
- U osmolality over 500
prerenal
prerenal vs intrarenal vs postrenal
- urine Na over 20
- serum BUN:Cr under 10
- FENa over 1%
- Sp Gr under 1.012
- U osmolality under 250
intra-renal
what GFR is considered moderate CKD3 & signals need to refer?
30-59
what GFR signals dialysis?
under 15
this measurement is determined by # and size of particles in the urine & varies with osmolality. what is the normal range for this lab value?
Specific gravity
normal is 1.005 to 1.025
osmolality is more accurate & is determined by # of particles only
what is the normal pH range for urine?
4.5 to 8.0; usually 6.0
uncontrolled DM, starvation, dehydration, protein changes your urine pH in what way?
makes it acidic
chronic renal failure, salicylate intox., proteus infection changes your urine pH how?
makes it alkaline
persistent proteinuria is classified into what 3 ways?
glomerular
tubular
overflow
what class of persistent proteinuria is this
- may cause massive proteinuria & has many causes
- albumin is primary protein
glomerular
what type of persistent proteinuria
- malfunctioning tubule cells don’t metabolize or reabsorb normally filtered protein
- LMW proteins predominate
- rarely exceed 2g/day
tubular
what type of persistent proteinuria
- LMW proteins overwhelm ability of tubules to reabsorb filtered proteins
- can be seen in multiple myeloma?
overflow
what do you do if there is mild proteinuria on dip in an asymptomatic patient
recheck the dipstick
it can be transietnt d/t many things
4 things to do if there is proteinuria in a non-asymptomatic patient
- get 24hr urine
- microscopic exam of urinary sediment
- urinary protein electrophoresis
- assess renal function
you get a 24 h urine test and the value is under 3g/24hrs what type of disease is this? over 3g/24hrs?
- under 3g: glomerular or tubular disease (nephritic)– could be either but tends to be tubular
- over 3g: nephrotic range, typically glomerular
what is this called?
excretion of 30-150mg of protein/day found via other test (not dipstick); affected by hydration status and indicates renal tubular disease
microalbuminuria
- if patient has this + DM, should start ACEi
if patient has glucosuria but not DM after checking for it, what is likely happening?
its renal tubular disease
other than diabetes & diets, what are 3 other times you may expect to see ketones in urine
- strenuous exercise
- frequent vomiting
- pregnancy
bilirubin vs urobilinogen– which is normally found in urine in small amounts?
urobilinogen
if someone has microscopic hematuria w/o e/o renal dz, what do we do? why?
recheck it in weeks & if still present, refer to urology
because it can be serious urologic disease or malignancy
transitional epithelial cells means what?
can be normal but if in large amounts may suggest a UTI
which type of cells seen in microscopic UA is the desquamation of tubular epithelium that suggests significant renal pathology
tubular epithelial cells
over ____ is significant bacteriuia in asymp. pt while over ____ suggests UTI in pt w/ sx. what should you do after diagnosing bacteriuria?
- over 100K mL in asymptomatic = significant bacteriuria
- over 100 mL in sx suggests UTI
- after dx, need C & S (culture and sensitivity)
what type of cast?
- small # w/ exercise, dehydration, stress, pyelonephritis but may be normal
- from distal tubules
- protein w/o cellular inclusion
hyaline cast
what type of cast
- # of casts increses w/ severity of disease
- indicates glomerulonephritis
RBC cast
what type of cast
- seen w/ renal tubule dz
- seen in ATN, interstitial nephritis, eclampsia, nephritic syndrome
epithelial casts
what type of cast
- made up of various cell types in final phase of cellular degeneration
- very slow tubular transit time
- severe chronic renal disease (HTN nephropathy)
waxy/granular casts
what type of cast
-indicates nephrotic syndrome, renal disease, hypothyroidism
fatty cast
what type of cast
made of various cell types and indicates ESRD
broad cast
colorless crystal w/ coffin lid appearance associated w/ alkaline urine & UTI (proteus species)
triple phosphate
colorless hexagonal shaped crystals found in acidic urine; diagnostic of cystinuria
cystine crystals
