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Blood tests
There are also several blood tests that can aid in evaluating
kidneyfunction. These include:
Blood urea nitrogen test (BUN).Urea is a by-product of protein
metabolism.This aste product is formed in the liver! then filtered
from the blood and
e"creted in the urine by the kidneys. The BUN test measures the
amount of
nitrogen contained in the urea. #igh BUN levels can indicate
kidney dysfunction!
but because blood urea nitrogen is also affected by protein
intake and liver
function! the test is usually done in con$unction ith a blood
creatinine! a more
specific indicator of kidney function.
%reatinine test. This test measures blood levels of creatinine!
a by-product of
muscle energy metabolism that! like urea! is filtered from the
blood by the
kidneys and e"creted into the urine. &roduction of
creatinine depends on an
individual's muscle mass! hich usually fluctuates very little.
ith normal kidney
function! then! the amount of creatinine in the blood remains
relatively constant
and normal. or this reason! and because creatinine is affected
very little by liver
function! an elevated blood creatinine is a more sensitive
indication of impaired
kidney function than the BUN.
*ther blood tests. +easurement of the blood levels of other
elements
regulated in part by the kidneys can also be useful in
evaluating kidney function.
These include sodium! potassium! chloride! bicarbonate! calcium!
magnesium!
phosphorus! protein! uric acid! and glucose
&reparation
%ertain dietary and,or medication restrictions may be imposed
for some of the
blood tests. The patient may also be instructed to avoid
e"ercise for a period of
time before a test.
ftercare
f medication as discontinued prior to blood kidney function
test! it may be
resumed once the test is completed.
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/isks
/isks of these tests are minimal! but may include slight
bleeding from a blood
draing site hematoma ( accumulation of blood under a puncture
site) or fainting
or feeling light headed after venipuncture. in addition
suspension of medication or
dietary changes imposed in preparation for some blood tests may
trigger side
effects in some individuals.
Normal results
Normal values for many tests are determined by the patient's age
and se".
Blood urea nitrogen (BUN).0-12 mg,dl
%reatinine. 2.0-3.1 mg,dl for males! and 2.4-2.5 mg,dl for
females
bnormal results
6o clearance values for creatinine indicate diminished ability
of the kidneys to
filter these aste products from the blood and e"crete them in
the urine. s
clearance levels decrease! blood levels of creatinine increase.
7ince it can be
affected by other factors! an elevated BUN! by itself! is
suggestive! but not
diagnostic! for kidney dysfunction. n abnormally elevated blood
creatinine! a
more specific and sensitive indicator of kidney disease than the
BUN! isdiagnostic of impaired kidney function.
8ey terms
Blood urea nitrogen(BUN)-The nitrogen portion of urea in the
bloodstream. urea is a aste product of protein metabolism in the
body.
%reatinine- the metaboli9ed by product of cretainine! an organic
acid that
assists the body in producing muscle contractions. cretainine is
found in
the bloodstream and in muscle tissue. t is removed from the
blood by the
kidneys and e"creted in the urine!
