Renal Labs Flashcards
what are the 3 types of urinalysis
- dipstick = fast / cheap
- microscopic = evaluates sediment
- culture - tells us about infection
what are the indications for a urinalysis
desire to know something about urinary tract/ metabolic function
difference between clean catch and random sampling in UA
clean catch= steps to limit contamination by skin bacteria (cleansing area, collecting mid stream)
random is used more for drug screening, etc where bacteria will not matter
when might you use a catheter to obtain a UA
to avoid menstrual blood OR
in pt that is unable to perform a clean catch on own
how quickly do UA samples need to be evaluated
right away or refrigerate
things analyzed on a UA
this is the order of what comes fastest to slowest
glucose bilirubin ketone blood pH protein urobilinogen nitrite leukocyte specific gravity
NOT CREATININE
how do you analyze urine with microscope
assess color, clarity and then spin sample
poor off most fluid, resuspend sediment and examine with scope
looking for cells, casts, crystals, microbes
HPF x 400
when might you run a urine culture
if you suspect infection of urinary tract
you usually request the test for sensitives as well
sensitivity= shows what antibodies that bacteria will be killed by
how would you collect urine for a urine culture
clean catch or catheter
organisms grow on media
when interpreting a urine culture, what does high numbers mean
likely cause of infection
few or no colonies= infection not likely
what does proteinuria indicate
if persistent: renal disease
if transient: febrile illness, CHF, exercise
what are methods to obtaining proteinuria
UA dipstick - rough estimate
24 hour urinary protein- gold standard
protein to creatine ratio
microalbuminuria
what is 24 hour urine collection
collecting each void within a 24 hour time frame, should be kept in refrigerator or with preservatives
what are blood tests that you may order (esp when concerned about renal function
creatinine
BUN
(usually both included on either a CMP or BMP) metabolic panels
what does creatinine measure
how to collect
it is used as the estimation for glomerular filtration rate
to collect you need nonfasting blood draw OR urine sample
it is a breakdown product of creatine phosphate
when would it be indicated to get a creatinine measure
blood test: to evaluate renal status (acute/chronic)
urine= estimating proteinuria or calculating creatinine clearance
what does a high serum creatinine indicate
impaired renal funciton
also large spread muscle injury (rhabdomyolysis)
increased muscle mass
what does a low serum creatinine indicate
decrease in muscle mass
what is the general rule in regards to creatinine
doubling of creatinine in serum indicates a 50% decline in GFR
BUN
- indications
- collection
Blood urea Nitrogen
indication: renal status evaluation or liver function
collection: nonfasting blood specimen
what does a decreased BUN indicate
low= less urea made (liver failure, malabsorption/malnutrition) OR urea diluted (pregnancy, fluid overload)
what does an elevated BUN indicate
if it is pre-renal cause= increased BUN before kidney
-causes: shock, hypotension, dehydration, CHF
if it is postrenal= increase BUN after kidney
causes= urinary tract obstruction
kidney disease= increases BUN
what is GFR estimates not helpful for
acute RF
may be normal values despite severe disease
what are types of azotemia
- prereneal: increased BUN before reaches kidney: shock, hypotension, dehydration
- postrenal: increased BUN after leave kidney. Urinary tract obstruction
- renal/intrinsic: kidney disease
what test is used to measure GFR
creatinine clearance- estimates
insulin is ONLY used in research - direct measure
how do you measure creatinine clearance
collect urine X24 hours and one blood draw for serum creatinine then perform calculations
mL/min
when is it indicated to get creatinine clearance
evaluation of kidneys filtering ability needed
collection of creatinine clearance
24 hour collection PLUS single nonfasting blood specimen
interpretation of creatinine clearance results
what does a high one mean
what does a low one mean
high= not commonly encountered- exercise, preg, increased CO syndromes
LOW!
- impaired renal function and or impaired flow to kidney
need to adjust meds, dialysis considerations
what equation is used to calculate the CrCl
cockcroft gault formula
takes into account age, weight (based on ideal body weight) and gender
what is the BUN : CrCl ratio
why is it important
both freely filtered by glomerulus
but BUN is reabsorbed in tubules to be regulated
creatinine remains the same throughout so can compare the funciton of nephron
if BUN: CrCl ration is >20:1 what does that indicate
pre renal
BUN reabsorption is increased
BUN is disporportionaly elevated relative to creatinine in serum
remember BUN measured with blood
If 10-20: 1 BUN: CrCl what does that mean
normal or post reanal
<10:1 BUN:CrCL ratio what does that mean
intra renal
renal damage reduces absorption of BUN therefore lowering the BUN:Cr ratio
what is the gold standard for imaging the kidney
CT
when doing a CT of the kidney you should not use contrast, why
contrast can cause nephropathy
must check creatinine / BUN prior to contrast
what percentage of cardiac output goes to kidneys
20-25%
pt with left side and back pain with blood in urine (urine dipstick positive) also nauseated
what do you suspect
ureterolithiasis
for ureterolithiasis (kidney stones) what do you order
what if pt pregnant
CT of KUB (kidneys, ureters’, bladder)
gold standard
if patient is pregnant - renal ultrasound better option (no radiation)
post surgery checkup, diagnosed with benign prostatic hypertrophy - surgery 5 weeks ago
catheter removed 2 weeks ago
not feeling well past week, back/side/groin pain and increased urgency/burning with urination
vitals reveal fever and increased heart rate
pyelonephritis
order a UA/culture before antibiotics
and prescribe antibiotics
pt with LLQ abd pain and fever getting CT scan with oral and IV contrast
history of DMII (type 2 diabetes) and milk HTN controlled with diet and lisinopril
what do we need to know about kidneys before she is given IV contrast
creatinine clearance - make sure working okay
and BUN ???
then use equation
keep in mind female, ideal weight, age
what is the CrCl equation
(140-age) X (weight)
/
SCr ni mg/dL X 72
multiply final value by 0.85 because female
