DESCRIPTION

• Urinary tract infection (UTI) is defined by having pyuria and ≥50,000 colony-forming units (CFU)/mL of a single urinary tract pathogen from an appropriately collected specimen.
• Upper tract infection or pyelonephritis is the infection of the kidney parenchyma.
• Lower tract infection or cystitis: infection limited to the bladder
• Cystitis and pyelonephritis can be clinically indistinguishable.

EPIDEMIOLOGY

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

ETIOLOGY

Urinary tract pathogens

• Escherichia coli is responsible for >80% of UTIs in children.
• Other common microbes include Klebsiella species, Enterococcus, and Proteus mirabilis.
• UTI can be diagnosed in absence of pyuria when organisms like Enterococcus, Klebsiella, and Pseudomonas are present with significant growth.
• Less common
  • Enterobacter cloacae
  • Group B hemolytic streptococci
  • Citrobacter
  • Pseudomonas species
  • Staphylococcus aureus
  • Serratia species
  • Staphylococcus saprophyticus (adolescent girls)
• For children with classic UTI symptoms but negative culture, viral cystitis is a common pathogen.

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 the highest risk of UTI.
  • Prevalence is 10 times higher for uncircumcised males versus circumcised males <3 months of age.
• Bowel and bladder dysfunction such as constipation is a major risk factor in toilet-trained children.
• Abnormal urinary tract: Children with vesicoureteral reflux (VUR) are at higher risk for UTI.
• Poor bladder emptying (neurogenic bladder, obstructive uropathies) leads to an increased risk of bacterial growth in stagnant urine.
• Frequent catheterization
• Sexual activity
• Conditions that alter vaginal microbiota such as use of spermicidal birth control methods or recent antibiotics

GENERAL PREVENTION

• Teach correct wiping (e.g., wiping from front to back) to young children. Attention to good voiding and stooling habits; treat constipation.
• Antibiotic prophylaxis has been shown to be efficacious in certain patient groups, depending on the study.
• Advise parents against bubble baths and encourage showers.
• Cranberry juice has not been shown to help.

PATHOPHYSIOLOGY

• Microbiota 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.

COMMONLY ASSOCIATED CONDITIONS

• VUR
• Urinary abnormalities
• Bowel and bladder dysfunction
• Tethered cord syndrome
• Approximately 5–10% of infants with febrile UTIs (pyelonephritis) have bacteremia, but the clinical course is likely unchanged.
• Unless infants 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.