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Urinalysis
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What is the
test?
A urinalysis is a routine examination of the
urine for cells, tiny structures, bacteria, and
chemicals that suggest various illnesses. A urine
culture attempts to grow large numbers of bacteria
from a urine sample to diagnose a bacterial urine
infection.
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How
do I prepare for the test?
For a regular urinalysis, you are asked to urinate
briefly into a plastic cup. When urine is collected
for a urine culture, you must provide a "clean
catch" sample - one that is not contaminated
by skin cells and skin bacteria. This is so the
doctor can obtain a sample of urine from inside
your bladder, where normally there should be
no bacteria. In contrast, there are many bacteria
on the skin of a penis or in a vagina. The trick
(harder for a woman than a man) is to pee directly
into a sterile container without having the stream
of urine first touch your skin or the nonsterile
tissues of the vagina.
To collect a clean catch sample, you are given
a sterile plastic container and asked to wipe
off the area around your urethra (where urine
exits) with an antiseptic cloth. For women, it's
also helpful to hold the two labia (outer walls)
of the vagina apart with one hand when you urinate,
so that the stream of urine passes directly into
the sterile container. Since the first flow of
urine is most likely to be contaminated by bacteria
from around the opening of the urethra, first
urinate for a moment into the toilet and then
use the cup to collect the "middle" portion of
your urine stream.
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What
happens when the test is performed?
For a regular urinalysis, your urine is tested
both chemically and by microscopic exam. Chemical
examination uses a
"dipstick" to reveal the pH (acidity) and concentration
of your urine, while simultaneously testing for
several chemicals at once. Some chemicals indicate
that blood in general and white blood cells in
particular might be present, a sign of a urinary
infection, kidney stones, or other problems.
Nitrite, a chemical produced by most bacteria,
suggests a bacterial infection. Sugar in the
urine is a sign of diabetes (high blood sugar),
while chemicals known as ketones can indicate
a diabetic complication. Protein in the urine
can indicate kidney disease or impaired kidney
function.
A microscopic examination is done after the urine
is spun inside a tube in a centrifuge. This concentrates
the solid particles at the bottom of the tube,
so they can be studied more easily.Microscopic
examination can show red blood cells, white blood
cells, bacteria, crystals, skin cells that might
have contaminated the sample, and, rarely, parasites
in your urine. In some cases, the way the cells
look offers your doctor clues about whether they
entered your urine from the bladder or the kidney.
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What
risks are there from the test?
None.
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Must
I do anything special after the test is over?
No.
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How
long is it before the result of the test is
known?
Your doctor might be able to do a urinalysis
in his or her office and can give you the results
within 10-15 minutes. If the urine is sent to
a separate laboratory, it usually takes several
hours to get results, so you may not hear from
your doctor until the next day. A urine culture
takes 24 to 72 hours to complete, so you may
not hear results for several days.
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