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The decrease in pediatric sepsis, meningitis, and occult bacteremia over the past two decades due to successful immunizations has made urinary tract infection (UTI) a relatively more common cause of fever in young children, and UTI is now the most common serious bacterial infection in children. Consider UTI as a possible diagnosis in all febrile infants and young children presenting to EDs, and in all older children with abdominal or urinary symptoms whether or not there is fever.

Estimates of UTI prevalence are highly variable depending upon the population. Approximately 1% of boys and 3% of girls are diagnosed with UTI before puberty.1 Among young children presenting to EDs with fever and no obvious source of infection, between 3% and 8% have UTI.2,3 Younger age, non-black race/ethnicity, female sex, and uncircumcised male are some of the baseline characteristics that increase the risk of UTI (Table 126-1).2–4 For example, male and female infants <3 months of age have a higher prevalence of UTI than older infants and toddlers.3 It is unclear why black children have a lower risk of UTI, but this has been consistently noted in studies of UTI prevalence.5

Table 126-1 Factors That Affect Prevalence of Urinary Tract Infection

Young children with UTI usually have upper tract involvement and fever, and older children tend to develop isolated cystitis without systemic involvement. Determining the baseline prevalence of UTI based on demographic and historical information allows for more informed decisions about subsequent diagnostic testing and treatment.

UTI is most commonly caused by bacteria, although viruses and other infectious agents can also be urinary pathogens. The vast majority of UTIs in all age groups occur when perineal-fecal bacteria ascend the urethra and enter the bladder. Escherichia coli is the most common cause of UTI in children, and this is likely due to its ubiquitous presence in stool combined with bacterial virulence factors that improve adhesion and ascent of the urethra.1 Mechanical defenses in humans, such as normal urinary outflow, clear most bacteria that are introduced into the bladder. Anatomic abnormalities can make bacterial proliferation or persistence in the bladder more likely. There are occasionally patients, usually preschool or school-aged females, who have recurrent UTI without a clear anatomic abnormality. Some of these patients likely have abnormal bladder function due to constipation, whereas others will not have any identifiable risk factors. Rare causes of UTI in children include indwelling urinary catheters or UTI from embolism or secondary to infection of other body areas.


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