clinical tools Flashcards
problem with serum creatinine as measure of GFR
small changes in the low range result in dramatic calculated changes in GFR, so better to measure over time
increased creatinine reflects ____ GFR
decreased
how do you correct SCr for differences in muscle mass due to age, ethnicity, and sex?
use the MDRD equation
creatinine clearance is preferred over SCr in patients with?
near normal GFR, pregnancy, amputees, severe liver dz, extremes of age and weight
how do you calculate creatinine clearance?
(urine creatinine X total urine volume)/(plasma creatinine*1140min/day)
MDRD should be used when GFR is?
less than 60
___ is expensive but very accurate at detecting residual GFR
radionucleotide GFR scanning
who should receive radionucleotide GFR scanning?
pts with CKD, impaired GFR, renal cell carcinoma, pre-transplant in cases of advanced liver dz, liver donors
when should a CKD pt be considered for dialysis?
plot eGFR over time and consider dialysis when consistent/linear decline results in eGFR below 10
urine protein/creatinine ratio is used to estimate urinary protein excretion because?
it is unaffected by urine volume or concentration
urine protein/creatinine ratio is effective for protein excretion in what range?
0.3-3g (overt proteinuria)
if urine protein excretion is less than 0.3g, then you should use the ___ instead
albumin/creatinine ratio (less than 30mg in normal)
red urine is a sign of..
secondary tumor of bladder (gross hematuria)
tea colored urine is a sign of?
glomerular hematuria
if urinalysis shows a dramatic change in protein after sulfa-salicylate is administered, then this is a sign of?
light chains (multiple myeloma)
detection of nitrites and leukocyte esterase on urine dipstick indicate?
UTI
exogenous solute will ____ urine osmolarity relative to urine specific gravity
decrease
these renal injuries do not affect urine sediment
pre-renal, post-renal
RBCs, RBC casts, and proteinuria are signs of?
glomerulonephritis, vasculitis, TMA, atheroemboli
WBCs, WBC casts are signs of?
pyelonephritis, interstitial nephritis
eosinophils in the urine are a sign of?
allergic IN, atheroemboli, glomerulonephritis
RTE cells, pigmented casts are a sign of?
tubular endothelial injury (ATN): ischemic or nephrotoxic
monomorphic red cells are typically seen with?
UTI, tumors, stones
dysmorphic red cells are typically seen with?
glomerulonephritis (parenchymal dz)
acanthocytes look like _____ and are a sign of?
“Micky Mouse” cells; glomerulonephritis
squamous epithelial cells in urine are a sign of?
poor urine specimen (not midstream)
transitional epithelial cells are ____ than renal tubular epithelial cells and indicate?
larger; inflammatory process (UTI, catheter) as opposed to renal tubular injury
the combination of white cells in urine + bacteria is consistent with?
urinary tract infection
why do “casts” form in the urine?
Tamm-Horsfall protein gels in conditions of high concentration (collecting duct, distal tubule), creating casts that are reflective of tubule contents
hyaline casts are made of ___ and seen in states of?
only tamm-horsfall protein; hypovolemia or decreased renal perfusion
evolution of a cast over time?
course granular -> broad/fine granular -> waxy
coarsely granular casts are indicative of?
renal parenchymal disease (acute or chronic)
muddy brown casts are composed of ____ and indicative of ____
necrotic tubular epithelial cells; ATN (ischemic or nephrotoxic)
white cell casts are indicative of?
interstitial nephritis or pyelonephritis
fine granular casts are indicative of?
renal parenchymal disease (acute or chronic)
fatty casts are seen in?
patients with nephrotic range proteinuria
how do you make a fatty cast stand out?
polarizing microscopy (lipoproteins look like Maltese Crosses)
oval fat bodies are _____ and are most commonly seen in?
epithelial cells with excess lipoprotein; nephrotic syndrome or severe ATN
waxy casts are most commonly seen in?
advanced chronic kidney disease (nephrons with especially decreased flow)
uric acid crystals are ____ shaped, form in urine when the pH is ___, and are seen in?
tear; <5.5; uric acid stones or tumor lysis syndrome, sometimes type 2 diabetes
calcium oxalate crystals are shaped like ____ and most commonly seen in…
pyramids (look like a cross from top view); typical kidney stones or ethylene glycol poisoning
an increased anion gap and increased osmolar gap suggests?
ethylene glycol poisoning
crystine crystals are ____ shaped and indicate?
hexagon; a defect in the dibasic aminoacid transporter (rare, but more common cause of stones in kids)
“coffin-lid” shaped crystals are made of _____ and typically seen in the setting of?
Mg-Ammonium-Phosphate; very high urine pH (>7) such as chronic UTI with urea-splitting organisms
triple phosphate crystals are known as ____ stones; how are they excreted?
struvite; often very large and have to be surgically removed
rosette or spindle shaped crystals are made of _____ and form when urine pH is _____
calcium-phosphate; >6
who gets calcium-phosphate stones?
type 1 distal RTA, tumor lysis syndrome
