New definition of UTI means fewer young children need invasive tests

A 4-year-old girl in for her well visit gives a routine urine sample. She has no urinary symptoms and no fever but there’s a trace amount of blood in the urine on dipstick. The urine is sent to the lab where a culture is done and grows more than 100,000 colonies of E.coli.

A 6-month-old uncircumcised boy is in the office with a fever but no clear source of infection. A catheterized urine sample is obtained. The dipstick urinalysis is completely negative but to be complete a culture is sent which grows 50,000 colonies of E.coli.

An 18-month old girl comes in with mom complaining of foul smelling urine and fussiness. A urine sample is gotten via catheterization and the urinalysis shows white blood cells and some leukocyte esterase (a by product of white cells when in contact with bacteria). Her culture grows 50,000 colonies of E. coli.

As recently as a year ago, all three of these children would have been labelled as having a urinary tract infection. All three would have had an ultrasound to look for structural abnormalities and the younger two would have also had an invasive dye test called a voiding cystourethrogram (VCUG) to determine if when the child urinates, the pee backwashes up toward the kidneys (a condition called urinary reflux). Now though only one of the children described above would have any tests at all, the 18 month old girl.

We used to think that the bladder is a sterile area but it appears that having bacteria in the urine is more common than we thought. As a result, it has become clearer over time that it takes more than just the presence of bacteria to indicate infection. I know that sounds a little crazy but if you think about it, we all have tons of normal bacteria in our intestinal tract and sometimes those bacteria can find their way into our urethras. We all flush these bacteria out naturally through urination and we’re never the wiser. Sometimes we happen to obtain a urine sample at a time when those bacteria are around and in the past the presence of any bacteria has been thought to be pathologic. Now the guidelines for young children, over 2 months of age mandates that both bacteria and pyuria (white blood cells in the urine indicating the body is launching an attack against the bacteria) need to be present for the diagnosis of a UTI to be made.

By narrowing the definition of a urinary tract infection with these criteria, many fewer children will undergo unnecessary and invasive tests.