Why does the collection method matter?
Urine is sterile in the kidney, but on its way out it can be contaminated by bacteria on the skin and genitals. In a sample that is not collected correctly, bacteria are “found” and the child gets unnecessary antibiotics, or the opposite happens and a real infection is missed.
In children who use the toilet
- Hands are washed.
- The genitals are washed with water; soap and antiseptic are not needed. In girls, front to back; in boys, with the foreskin gently pulled back.
- The child starts to pass urine, and the first part goes into the toilet.
- The middle part is collected in a sterile container.
- The rest goes into the toilet again.
In babies
- Catheter sample: the reliable method for urinalysis and culture in babies and children who are still in diapers. It is taken by a health care worker with a very thin catheter. In some cases a doctor takes the urine with a fine needle through the lower belly (suprapubic aspiration).
- “Clean catch” method: 30–60 minutes after a feed, the diaper is opened, the genitals are washed and a sterile container is held ready. Lightly tapping the baby’s lower belly and lower back stimulates passing urine. It is acceptable for a first screening test.
- Urine bag: a bag stuck to the skin. It is easy, but the sample gets contaminated quickly, so it is not used for culture. A completely negative result makes infection unlikely, while a positive result must be checked with a catheter sample.
How is the culture read?
The laboratory counts the bacteria that grow from the urine. Growth of a single type of bacteria supports infection; how many bacteria count as significant depends on how the sample was collected. Growth of several different bacteria usually means the sample was contaminated and needs to be repeated.
Delivering the sample
- The sample should reach the laboratory within 1–2 hours.
- If delayed, it can be kept in the refrigerator (4°C) for up to 24 hours.
- Write the child’s name, the date and the time on the container.
Before antibiotics
When a urinary tract infection is suspected, the sample must be collected before starting antibiotics. Even a single dose of antibiotic can make the culture result falsely negative.
Note for pediatricians and family doctors
Plastic bags should not be used for urine sampling: a bag specimen has a high false-positive rate and is useful only when negative (dipstick negative for both leukocyte esterase and nitrite, or microscopy negative for pyuria and bacteriuria, excludes UTI). In non-toilet-trained children, urinalysis and culture require a catheter or suprapubic aspiration specimen; clean-catch urine (for example with Quick-Wee stimulation) is acceptable for screening. Toilet-trained children give a midstream sample. Pyuria: 5 WBC/HPF centrifuged (25/µL) or more than 10 WBC/µL uncentrifuged; nitrite alone is too insensitive under 2 years. Culture: 10⁵ cfu/mL is expected in febrile UTI, but clean-catch, midstream and catheter samples can be considered positive at 10³–10⁴ cfu/mL of a single organism; any growth from suprapubic aspiration is significant; in febrile infants under 4 months 10³ cfu/mL can be used when clinical and laboratory findings match; mixed growth suggests contamination.
What happens at the visit?
- When needed, the sample is collected at the clinic using the correct method.
- Urinalysis and culture results are assessed together with the symptoms.
Frequently asked questions
The test shows white blood cells. Is this an infection?
Not always. White blood cells are a sign of inflammation, but in girls they can also come from outside contamination, fever or other causes. The diagnosis is made from the symptoms and the culture of a correctly collected sample.
When will the culture result be ready?
Usually in 2–3 days. That is why, in a child with fever, antibiotics are started without waiting for the culture result and are adjusted later based on the result.
Related topics
Sources
- EAU Guidelines on Paediatric Urology, 2026: Urinary tract infections.
- Kaufman J et al. Faster clean catch urine collection (Quick-Wee method) from infants: randomised controlled trial. BMJ, 2017.
References to the EAU Paediatric Urology guidelines were checked against the 2026 edition (October 2026).
This information is for educational purposes and does not replace medical advice. Decisions about your child’s treatment are made with the doctor after an examination.
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