Chapter 132: Urinary Tract Infection in Infants and Children

INTRODUCTION AND EPIDEMIOLOGY

Pediatric urinary tract infections (UTIs) are now the most common serious bacterial infection in young children, since the introduction of successful immunizations and the resultant decrease in pediatric sepsis, meningitis, and occult bacteremia. UTIs should be considered 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 on the population. Pediatric UTI occurs in up to 8% of febrile children presenting to the ED with no obvious source of infection.^1,2,3 Approximately 1% of boys and 3% of girls are diagnosed with a UTI before puberty.⁴ The highest incidence occurs during the first year of life for both genders.³ Some of the baseline characteristics that increase the risk of UTI are listed in Table 132-1.^{1,2,5,6,7,8,9,10,11} It is unclear why African American children have a lower risk of UTI, but this difference is consistently noted.¹¹

PATHOPHYSIOLOGY

Bacteria most commonly cause UTIs, although viruses and other infectious agents can also be urinary pathogens. The vast majority of UTIs in all age groups typically occur from retrograde contamination of the lower urinary tract with organisms from the perineum and periurethral area. In neonates, however, UTIs typically develop after seeding of the renal parenchyma from hematogenous spread.

Escherichia coli is the most common cause of UTI in children, and this is likely because of its ubiquitous presence in stool combined with bacterial virulence factors that improve adhesion to and ascent of the urethra.⁴ Additional pathogens include Klebsiella, Proteus, and Enterobacter species. Enterococcus species, Staphylococcus aureus, and group B streptococci are the most common gram-positive organisms and are more common in neonates. Staphylococcus saprophyticus can cause UTI in adolescents, and Chlamydia trachomatis may be present in adolescents with urinary tract symptoms and microhematuria. Adenovirus may cause culture-negative acute cystitis in young boys.

Mechanical defenses in humans, such as normal urinary outflow, clear most bacteria that are introduced into the bladder. Anatomic abnormalities can make ...