Urinary Tract Infection



  • Urinary tract infection (UTI) is defined by having pyuria and ≥50,000 CFUs/mL of a single urinary tract pathogen from an appropriately collected specimen.
  • Upper tract infection or pyelonephritis: infection of the renal parenchyma; most febrile babies with a positive culture have upper tract infection.
  • Lower tract infection or cystitis: infection limited to the bladder, not involving the kidneys; occurs more in older children and adolescents; usually no fever
  • Cystitis and pyelonephritis can be clinically indistinguishable.


  • Bimodal age distribution with peak incidence in infants <1 year of age (40 per 1,000)
  • Second peak in adolescent females
  • Overall prevalence of about 7% in febrile infants and young children; varies according to risk factors below
  • Higher prevalence in Caucasian girls

Risk Factors

  • Sex/age: Boys are most at risk for UTI during 1st year of life; girls until school age and again in adolescence
  • Circumcision status: Uncircumcised males <1 year of age have increased risk of UTI; prevalence is 10 times higher for uncircumcised males versus circumcised males <3 months of age.
  • Race/ethnicity: Caucasian children are 2 to 4 times more likely than African American children to have UTI:
    • May be due in part to genetic differences in blood group antigens on the surfaces of uroepithelial cells, which affect bacterial adherence
  • Abnormal urinary tract: Children with vesicoureteral reflux (VUR) are at higher risk for UTI.
  • Poor bladder emptying (neurogenic bladder, obstructive uropathies) increase risk of bacterial growth in stagnant urine.
  • Bowel and bladder dysfunction is a major risk factor in toilet-trained children.
  • Requiring frequent catheterization
  • Sexual activity
  • Conditions that alter vaginal flora such as use of spermicidal birth control methods or recent antibiotics
  • Clinical decision rule in febrile girls 2 to 24 months of age. Consider testing if ≥3 of following are present:
    • Temperature ≥39°C, fever for ≥2 days, non-African American race, age <1 year, absence of another potential source of fever

General Prevention

  • Teach correct wiping—front to back—to young children.
  • Consider prophylactic antibiotics for select children with recurrent infection, high-grade VUR, bowel/bladder dysfunction, and urologic anomalies.
    • There is controversy in the literature about the effectiveness of antimicrobial prophylaxis. It has not been shown to reduce renal scarring.
  • Attention to good voiding and stooling habits; treat constipation.
  • Consider single-dose postcoital antibiotics for adolescents with recurrent UTI.
  • Cranberry juice has not been shown to help.


  • Flora from skin or gut ascend the urethra and adhere to the uroepithelium, triggering local inflammation.
  • Various virulence factors make certain bacteria more likely to ascend and adhere.
  • Shorter urethra in females may put them at increased risk; in young infants, can be from hematogenous spread


Urinary tract pathogens

  • Escherichia coli is responsible for >80% of UTIs in children.
  • Other fairly common microbes include Klebsiella species, Enterococcus, and Proteus mirabilis.
  • Less common: Enterobacter cloacae, group B hemolytic streptococci, Citrobacter, Pseudomonas species, Staphylococcus aureus, Serratia species, and Staphylococcus saprophyticus (teenage girls)
    • Viral or fungal causes of UTI also possible

Commonly Associated Conditions

  • ~5–10% of babies with febrile UTIs (pyelonephritis) are bacteremic, but the clinical course is likely unchanged.
  • Unless they are ill-appearing on presentation or have significant underlying medical problems, infants with UTI have a very low risk of meningitis or other adverse events.
  • VUR, urinary abnormalities, bowel and bladder dysfunction

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