Urine Test: 24-Hour Analysis for Kidney Stones

What Is a Urine Test?

Testing a urine sample can help doctors find out what's going on when someone has an infection or other problem in kidneys, bladder, or other parts of the urinary tract.

To help your child get ready for a urine test, find out if they need to avoid any specific foods or activity before the test, or should stop taking any medicines.

Urine tests are painless. To help ease any fears, explain in simple terms how the test is done and why it's needed.

What Is a 24-Hour Analysis for Kidney Stones?

Doctors sometimes order a 24-hour urine analysis for kids who have a kidney stone. This test measures how much pee a child’s body makes in a day, the acidity (pH) of the pee, and how much of things like calcium, sodium, uric acid, oxalate, citrate, and creatinine are in it.

Why Are 24-Hour Analysis for Kidney Stones Done?

Kidney stones develop when salts or minerals build up in pee and form crystals. The crystals stick together and get bigger, eventually forming a hard mass called a stone.

A 24-hour urine analysis can see if there are high levels of some things in the pee that might cause kidney stones. Urinary pH is also important, as some crystals are more likely to form when pee is too acidic (low pH) and others are more likely to form when it’s not acidic enough (high pH).

The results, along with other tests like blood tests and radiology studies, can help doctors find the cause and location of the stones, and plan treatment that might help prevent more kidney stones. After treatment starts, another 24-hour urine collection can help show if it’s working.

How Is the Test Done?

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 doctor will give you a container to use to collect your child's pee over a 24-hour period.

• To begin: After waking up in the morning, your child should pee into the toilet (not the container) to empty their bladder. Write down the time this is done — this is the start of the collection period.
• For the rest of the day: Your child should pee into the container. During the testing period, collect all the pee, even if it’s just a small amount. 
• The next morning: Your child should pee into the container (not the toilet). This is the end of the 24-hour collection period. Write down the time of this last collection.

If your child isn't potty trained and can't pee into a cup, you might use urine collection bags with adhesive tape on one end to collect the samples. Clean the skin around the urinary opening (the urethra), place the bag around it, and secure with the attached tape. Your child can wear a diaper over the bag. Change the bags often to collect all the pee, and empty the bags into the special container.

Sometimes, doctors might insert a catheter (a narrow, soft tube) into the child’s bladder and leave it there for 24 hours to get a urine collection.

Cap the collection container and store it as you’ve been instructed during the collection period. Take the container to the lab your doctor recommended. 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 to your doctor.

What if I Have Questions?

If you have questions about the 24-hour urine analysis, speak with your doctor.