The conventional wisdom about urinary tract infections has changed over the years, but we still don’t have consensus regarding many of its management issues.
When I was an intern in 1972, it was relatively simple. We would admit a child with a UTI to the hospital, start antimicrobial therapy, do an intravenous pyelogram after a negative urine culture, and keep the child on antibiotics for a month until the follow-up vesicoureterogram (VCUG). But in the 1980s, people began to question the evidence for spending resources on imaging and for promoting antimicrobial resistance when it may not be necessary. We have more evidence today, but still no global consensus on the issues.
We do know that UTIs are common in children of all ages, but the main concern is for those in the under-2-year age group, where there is the greatest risk for renal damage that can result from treatment delayed beyond 72 hours of fever. Vesicoureteral reflux is far more common in this age group and tends to remit with increasing age. There is also agreement that evaluation for UTI is essential for any child in that age range who has had unexplained fever for more than 24 hours. Approximately 5% will be positive.
We have data to guide our decisions regarding who is at greatest risk for UTI. It is higher in females than males, with a 2-to-1 ratio in the first year of life and 4:1 in the second. But among boys, those who are uncircumcised have a 15- to 20-fold higher UTI rate than among those who are circumcised (Pediatrics 1989;83:1011-5).
Since the advent of the 7-valent pneumococcal conjugate vaccine (PCV7), we have seen Escherichia coli increase proportionally as a cause of bacteremia as a result of the decline in pneumococcal disease (Arch. Dis. Child. 2009;94:144-7). However, the overall rate of positive urine culture among children aged 3-36 months presenting to the emergency room with fever has not changed with PCV7, remaining at approximately 7%.
There’s controversy regarding UTI screening. Urine culture is the gold standard, with identification of 10 white blood cells per high-powered field in unspun urine on gram stain. However, this is time consuming and requires an expertise that many practitioners have lost since their training.
The presence of leukocyte esterase and nitrites on dipstick has become a widely used screen for children at risk for UTI. They are highly specific for gram-negative UTIs, but not as good for detecting gram-positive organisms. Dipstick testing works best in ruling out a UTI: If both leukocyte esterase and nitrite tests are negative, the likelihood of a UTI is extremely low. If both are positive in a symptomatic at-risk child, it’s an indication to initiate therapy and obtain a culture to confirm the infection, identify the pathogen, and determine its antimicrobial susceptibility.
While use of the two measures is considered an acceptable, rapid way to screen for UTI, there is a tradeoff. For every 1,000 children with compatible UTI signs and symptoms, these tests will identify greater than 90% of the children with culture-confirmed infection. However, as many as 20% of the children will be treated unnecessarily with antibiotics. This is a significant concern, given the potential for development of resistance.
Collecting the urine specimen is another area that lacks consensus. Urine collected in a bag is unreliable in children less than 2 years of age, and it’s not certain whether bag collection can be used in older children. Three culture collection strategies are recommended by the American Academy of Pediatrics (AAP) guideline committee report: suprapubic aspiration, catheterized specimen for girls/midstream stream in circumcised boys, or midstream clean void in girls or uncircumcised boys.
Suprapubic aspiration is the gold standard, but it’s more time consuming, difficult, and is associated with more discomfort. It is typically reserved for children less than 6 months of age. On the other hand, a single midstream clean void is just 80%-90% reproducible so some recommend a second specimen, especially in asymptomatic or minimally symptomatic children, to achieve greater (95%) reproducibility.
One area in which I do think the data are clear concerns the duration of therapy. Since approximately 50%-60% of children aged 2 months to 2 years with UTIs also have upper tract infection, there is a far better chance of cure and less chance of recurrence with 7-10 days of antibiotics vs. 3 days or fewer (Pediatr. Infect. Dis. J. 1988;7:316-9).
The most controversial areas in UTI management concern imaging and antimicrobial prophylaxis. Imaging, via sonogram plus either VCUG or radionuclide scan, accomplishes four goals: It localizes the infection (upper vs. lower tract), identifies the presence of reflux, identifies structural abnormalities, and detects renal scarring. But most structural abnormalities are already identified with prenatal ultrasound, and it’s not clear whether progression of renal scarring can be prevented with prophylactic antibiotics in children with reflux. Still, localizing the infection might help guide the duration of therapy, with longer courses used for those with upper tract disease.