What is the most common cause of urinary tract infections (UTIs) in children?

Most Common Cause of Urinary Tract Infections in Children

Escherichia coli (E. coli) is the most common cause of urinary tract infections in children, accounting for more than 90% of cases in young patients and approximately 71-86% of all pediatric UTIs. 1, 2

Epidemiology and Causative Organisms

UTIs are frequent bacterial infections during childhood, affecting:

• Approximately 2% of children assigned male at birth (AMB)
• Approximately 8% of children assigned female at birth (AFB) by 7 years of age 1

Distribution of Causative Organisms

• E. coli: 71-86.5% of cases 1, 2
• Klebsiella species: 13% of cases 2
• Proteus species: 11% of cases (predominantly in males) 2
• Staphylococcus species: 4% of cases 2
• Pseudomonas species: 1% of cases 2
• Other non-E. coli organisms: Associated with atypical UTI presentations 1

Age and Gender Distribution

• Infants: UTI prevalence in term neonates and young infants varies from 0.1% to 1%, with predominance in the first 2 months of life in neonates and young infants AMB 1
• First year of life: First peak of UTI incidence 1
• Ages 2-4 years: Second peak of UTI incidence, often associated with toilet training 1
• After age 6: UTIs become infrequent and often associated with dysfunctional elimination 1

Gender differences:

• UTIs are more common in females than males, except during early infancy 3
• Proteus infections are more commonly isolated from males 2

Clinical Presentation and Complications

UTIs in children may present as:

• Cystitis: Limited to the bladder with localized symptoms (frequency, urgency, dysuria)
• Pyelonephritis: Infection of kidneys with systemic symptoms (high fever, malaise, vomiting, abdominal/flank pain)

Complications:

• Renal scarring: The most severe long-term sequela, occurring in approximately 15% of children after first UTI episode 1
• Potential long-term risks: Hypertension and chronic kidney disease, though current evidence suggests the long-term risk is lower than previously thought 1, 3

Risk Factors for UTI

• Congenital urinary tract anomalies: Particularly vesicoureteral reflux (VUR) 1
• Previous UTI history: Increases risk for recurrent infections 1
• Female gender: Higher risk except in early infancy 3
• Atypical presentation: Includes serious illness, poor urine flow, abdominal/bladder mass, elevated creatinine, septicemia, failure to respond to antibiotics within 48 hours 1

Antibiotic Resistance Concerns

A significant concern in managing pediatric UTIs is increasing antibiotic resistance:

• E. coli resistance to ampicillin has increased from 53% to 69% over a 10-year period in some regions 4
• Resistance to trimethoprim/sulfamethoxazole increased from 34% to 55% 4
• Resistance to cephalexin increased dramatically from 4% to 36% 4

This highlights the importance of:

• Basing empirical antibiotic selection on local resistance patterns 5
• Obtaining urine cultures to guide targeted therapy 6
• Avoiding indiscriminate use of antibiotics in doubtful UTI cases 3

Diagnostic and Management Approach

For accurate diagnosis:

• Collection of an uncontaminated urine specimen is essential 3
• Both urinalysis and urine culture are needed to confirm true UTI 6

For treatment:

• Prompt antibiotic therapy (within 48 hours of fever onset) reduces risk of renal scarring 3
• Oral antibiotic therapy for 7-10 days is adequate for uncomplicated cases 3
• Imaging recommendations include renal ultrasound for all young children with first febrile UTI 3