Current guidelines may lead to untreated UTIs in children

As a pediatric urologist, I am frequently asked to give lectures on pediatric UTIs. It is always very humbling as ‘the expert’ to admit to the audience that I do not know the definition of a UTI. In fact, the definition of UTI varies across time and space. 

Different countries follow different organizations’ guidelines, which have different urine culture colony-forming unit (CFU) cutoffs for making the diagnosis of a UTI. These cutoffs also vary depending on the differently recommended techniques of obtaining the urine sample (ie, voided, catheterization, suprapubic aspiration). Over time, the AAP changed its definition of a UTI in children aged 2 to 24 months. The most recent AAP definition reduced the culture results cutoff from 100,000 CFU/mL to 50,000 CFU/mL but at the same time introduced a requirement for having pyuria. The thought process behind this was that a true infection as opposed to asymptomatic bacteriuria should cause some form of host response identified by pyuria on urinalysis. By restricting the definition of a UTI in this manner, the logic was that fewer children with harmless asymptomatic bacteriuria would be misdiagnosed as having a UTI and subjected to unnecessary treatment with antibiotics.

Shaikh and colleagues’ meta-analysis demonstrates that the prevalence of asymptomatic bacteriuria and asymptomatic bacteriuria with pyuria is at least an order of magnitude less than the prevalence of UTI. With these findings, the authors of the study make the valid point that it is a rare situation when a child with harmless asymptomatic bacteriuria would be diagnosed with a UTI. For this to happen, a preverbal child would need to have developed a febrile illness with nonspecific symptoms and have a urine sample collected that demonstrates no pyuria but a positive urine culture. 

Going further, the authors make the point that since the prevalence of asymptomatic bacteriuria is very low relative to the prevalence of UTIs, it is much more likely that among febrile preverbal children being tested for UTI, those with a true UTI will have a negative leukocyte esterase test and, therefore, the diagnosis of a UTI would be missed. The authors estimate that as a result of the AAP’s change in the definition of UTI, up to 12 children with true UTIs are being missed to protect one child with asymptomatic bacteriuria from receiving unnecessary antibiotics. Ultimately, this translates into children with pyelonephritis not receiving timely antibiotics, which increases the risk of kidney damage. and therefore, more harm than good is likely to be done by the requirement of a positive leukocyte esterase urinalysis test. 

Life was simpler when we falsely believed that urine was sterile. We now know this isn’t the case and that there is even a urinary microbiota. Although on a superficial level the logic behind the AAP’s requirement for a positive urinalysis to better define when bacteriuria becomes a UTI makes sense, the data from this and other studies show this is too simplistic. There are indeed children with a UTI and pyelonephritis who will have a negative urinalysis. In fact, multiple studies have demonstrated leukocyte esterase test is less likely to be positive when the uropathogenic organisms are Enterococcus, Klebsiella or Pseudomonas. A better urine test or marker is needed to help differentiate children with a UTI from those with asymptomatic and harmless bacteriuria. Unfortunately, in the meantime, clinicians cannot, and should not, rely on the urinalysis alone to rule out a UTI.