Urine collected in an adhesive bag is frequently contaminated by skin and perineal flora. A negative dipstick or microscopy on a bag sample is useful for making UTI unlikely in a well child. A positive culture from a bag specimen is not reliable enough to diagnose UTI.
When a bag sample suggests infection, or the child is unwell enough to need antibiotics, obtain a clean-catch, catheter or suprapubic sample before treatment. A diagnosis of UTI in an infant often leads to imaging and long-term labels, so the sample needs to be trustworthy.
- Use a negative bag sample to make UTI unlikely in a well child.
- Do not diagnose UTI on a bag culture; confirm with clean-catch, catheter or suprapubic urine.
- Collect the confirmatory sample before the first antibiotic dose.
- Record the collection method on the request; it changes how the culture is read.
Why it matters
A contaminated sample can label a child with UTI and trigger imaging they did not need.
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