Ketones
- urine
Alternative names
Ketone bodies - urine;
Urine ketones: acetone, acetoacetic acid, and
beta-hydroxybutyric acid
Definition
A test that measures the
presence or absence of ketones in the urine.
How
the test is performed
Child or adult:
Collect a "clean-catch" ("midstream") urine sample.
To obtain a clean-catch sample, men or boys should
wipe clean the head of the penis. Women or girls
need to wash the area between the lips of the
vagina with soapy water and rinse well. As you
start to urinate, allow a small amount to fall
into the toilet bowl (this clears the urethra
of contaminants). Then, in a clean container,
catch about 1 to 2 ounces of urine and remove
the container from the urine stream. Give the
container to the health care provider or assistant.
Infant:
Thoroughly wash the area around the urethra. Open
a urine collection bag (a plastic bag with an
adhesive paper on one end), and place it on your
infant. For males, the entire penis can be placed
in the bag and the adhesive attached to the skin.
For females, the bag is placed over the labia.
Place a diaper over the infant (bag and all).
Check your baby frequently and remove the bag
after the infant has urinated into it. For active
infants, this procedure may take a couple of attempts--lively
infants can displace the bag, causing an inability
to obtain the specimen. The urine is drained into
a container for transport back to the health care
provider.
Urine ketones are usually measured as a "spot
test" with a dipstick containing a color-sensitive
pad impregnated with specific chemicals which
react with ketone bodies. A color change is a
qualitative indicator of the presence of ketones.
How
to prepare for the test
A special diet may be recommended,
and drugs that may affect the test results should
be discontinued (see Special Considerations).
If the collection is being taken from an infant,
a couple of extra collection bags may be necessary.
How
it feels
The test involves only normal
urination, and there is no discomfort.
Risks
There are no risks.
Why
the test is performed
Ketones (beta-hydroxybutyric
acid, acetoacetic acid, and acetone) are the end-product
of rapid or excessive fatty acid breakdown. As
with glucose, ketones are present in the urine
when the blood levels surpass a certain threshold.
Fatty acid release from adipose tissue is stimulated
by a number of hormones including glucagon, epinephrine,
and growth hormone. The levels of these hormones
are increased in starvation (whether related to
excess alcohol use or not), uncontrolled diabetes
mellitus, and a number of other conditions.
Normal
values
A negative test result is normal. Results of
the presence of acetone in the urine are
usually listed as small, moderate or large with
these corresponding values:
small <20 mg/dL
moderate 30-40 mg/dL
large <80 mg/dL
What
abnormal results mean
A positive test may indicate
- metabolic abnormalities, including uncontrolled
diabetes or glycogen storage disease
- abnormal nutritional conditions, including
starvation, fasting, anorexia, high protein
or low carbohydrate diets
- protracted vomiting, including hyperemesis
gravidarum
- disorders of increased metabolism, including
hyperthyroidism, fever, acute or severe illness,
burns, pregnancy, lactation or following surgery
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