A 24-hour urine analysis is sometimes a part of an evaluation of a child who
has a kidney stone.
This test measures how much urine (pee) a child produces in a day, the acidity (pH)
of the urine, and the amount of certain substances in it, such as calcium, sodium,
uric acid, oxalate, citrate, and creatinine.
Why It's Done
Kidney stones develop when certain salts or minerals build up in the urine and
form crystals. The crystals stick together and enlarge, eventually forming a hard
mass called a stone.
A 24-hour urine analysis can show if certain substances are found at high concentrations
in the urine and might be causing the kidney stones. Urinary pH is also important,
as certain crystals are more likely to form in urine that's too acidic (low pH) and
others are more likely to form in urine that's not acidic enough (high pH).
The information from this test, in combination with other tests like blood tests
and radiology studies, can help determine the cause and location of the stones and
the treatment that might help prevent more kidney stones. Once treatment starts, another
24-hour urine collection can help determine whether the treatment is working.
This test is usually done after a child has already passed a kidney stone and is
feeling well, eating normally, and isn't being treated for a urinary tract infection
(UTI). Your child might need to temporarily stop taking specific drugs that could
interfere with test results. Be sure to review all your child's medications with your
Your doctor will give you a container in which to collect your child's urine over
the course of 24 hours. Upon rising in the morning, your child will be asked to urinate
into the toilet so that the test is begun with an empty bladder. You should note the
exact time this is done — this is the start of your child's urine collection.
For the rest of the day, all of your child's urine should be collected in the container.
The following morning, the first urine of the day should be collected as well, with
the time of day recorded. During the testing period, all the urine should be collected,
even if it is just a small amount.
If your child isn't potty trained and can't urinate into a cup, urine collection
bags with adhesive tape on one end might instead be used to collect the samples. Your
baby's genital area will need to be cleaned, and then the bag is placed around the
urinary opening and secured with the attached tape. A diaper can be placed over the
bag. The bag will need to be changed frequently to collect all of the urine, and each
bag will need to be emptied into the special container.
Another option is the use of a catheter (a narrow, soft tube), which can be inserted
into the bladder and left there for 24 hours to obtain urine.
The container should be capped and kept in the refrigerator or a cool place during
the collection period. Once all the urine has been collected, deliver the container
to the lab your doctor recommended. It is important to follow all the instructions
to correctly collect, store and transport the urine sample.
A laboratory technician will measure the urine volume and acidity level, and the
amount of specific substances in the urine, and will report these findings to your
What to Expect
Because the test involves normal urination, there shouldn't be any discomfort as
long as your child can provide a urine specimen. It's important to clean the area
around the urinary opening before each urine sample is provided.
Getting the Results
The results of the 24-hour urine analysis will be available within a few days.
If the test shows abnormal results, further tests may be needed. Talk to your doctor
about the meaning of the specific test results.
No risks are associated with the 24-hour urine analysis. Infants may occasionally
experience skin irritation from the adhesive tape on the collection bag. If a catheterized
specimen is required it may cause temporary discomfort and you can discuss any questions
you have about this procedure with your doctor.
Helping Your Child
The 24-hour urine analysis is painless. Explaining in simple terms how the test
will be conducted and why it's being done can help ease any fear. Make sure your child
understands that there should be no foreign matter, such as toilet paper or hair,
in the sample.
If You Have Questions
If you have questions about the 24-hour urine analysis, speak with your doctor.