Definition and epidemiology
Urinary tract infection (UTI) is among the commonest serious bacterial infections of childhood. By age 7, roughly 8% of girls and 2% of boys have had at least one UTI. Infection is described by site (cystitis vs pyelonephritis/upper-tract), by episode (first vs recurrent), and by severity/course (simple vs atypical/complicated). Escherichia coli causes ~80% of cases; Klebsiella, Proteus, Enterococcus and Pseudomonas are commoner with structural anomalies, instrumentation or prior antibiotics. The importance of UTI lies in its association with vesicoureteric reflux and the small risk of renal scarring, hypertension and CKD after recurrent or poorly-treated pyelonephritis.
Clinical features
Presentation is age-dependent and frequently non-specific:
- Infants/young children — unexplained fever, irritability, poor feeding, vomiting, lethargy, failure to thrive, prolonged jaundice in neonates. UTI must be actively excluded in any infant with fever without a source.
- Older children — the more localising dysuria, frequency, urgency, suprapubic pain, daytime/secondary enuresis, and loin pain or high fever (suggesting pyelonephritis).
NICE defines atypical UTI by any of: seriously ill/septic, poor urine flow, abdominal or bladder mass, raised creatinine, failure to respond to suitable antibiotics within 48 hours, or non-E. coli organism. Recurrent UTI is ≥2 episodes of upper-tract UTI, 1 upper + ≥1 lower, or ≥3 lower-tract episodes.
Diagnosis
Obtain urine before starting antibiotics, by the cleanest feasible method (clean-catch preferred; catheter or suprapubic aspirate in non-toilet-trained infants — avoid relying on bag specimens for diagnosis). Dipstick (leucocyte esterase and nitrite) guides under-3-year decisions cautiously, but culture is the standard, especially in infants. A pure growth of a single uropathogen at a significant colony count on an appropriately-collected sample confirms UTI. Localising imaging is not recommended routinely to determine the site of infection.
See the full criteria: Complicated/Atypical UTI Algorithm
Red flags
- Infant <3 months with fever — treat as high-risk; refer for parenteral antibiotics and full septic evaluation
- Septic appearance, dehydration, or inability to tolerate oral therapy
- Atypical features (poor urine flow, abdominal/bladder mass, raised creatinine, non-E. coli organism, no response by 48 h)
- Recurrent UTI or a known structural/functional urinary tract abnormality
Management overview
Empirical antibiotics are started promptly once urine is collected and tailored to local resistance and culture. NICE guidance:
- Lower-tract (cystitis): oral antibiotics for ~3 days (e.g. nitrofurantoin, trimethoprim, or amoxicillin-clavulanate / cephalexin per sensitivities).
- Upper-tract / pyelonephritis: oral antibiotics for 7–10 days where the child can take oral therapy and is not seriously ill; otherwise IV (e.g. a third-generation cephalosporin) for 2–4 days then switch to oral to complete 10 days.
- <3 months or seriously ill: parenteral antibiotics and specialist input.
Imaging is age-banded in the NICE NG224 tables (<6 months, 6 months–3 years, >3 years each carry different USS/DMSA/MCUG triggers — e.g. an infant <6 months with a responding first-time E. coli UTI still gets an ultrasound within 6 weeks); use those tables for the exact triggers. Broadly: ultrasound during the acute illness for atypical UTI (and within 6 weeks for recurrent UTI or non-E. coli infection responding well); DMSA scan 4–6 months later to detect scarring after atypical or recurrent UTI; MCUG considered selectively (younger infants, abnormal ultrasound/DMSA, family history of VUR, or non-E. coli/recurrent infection). Routine antibiotic prophylaxis is not recommended after a first UTI but is considered in recurrent UTI. Address bladder/bowel dysfunction and constipation. Counsel on prompt re-presentation with recurrence.
References
- NICE NG224. UTI in under 16s, 2022.
- ISPN revised statement on UTI management.
- AAP UTI clinical practice guideline (febrile infants 2–24 months).
Decision support for qualified clinicians only — verify against current primary guidelines and your clinical judgement.