Urinary Tract Infections in Children

❍ At a glance

• In infants under 2 years, fever without focus is the most common presentation of UTI - the classic adult symptoms are absent or unreliable. Missed UTI risks renal scarring, particularly after recurrent infection in young children.
• A bag specimen is unacceptable for culture. Clean-catch midstream urine is the minimum for culture in non-toilet-trained children. Catheter or suprapubic aspirate is required in infants under 3 months when a reliable culture is essential.
• A negative dipstick (negative nitrites and negative leucocyte esterase) has a negative predictive value of approximately 97% in children over 3 months. In children under 3 months, a negative dipstick does not reliably exclude UTI - send MC&S regardless.¹
• First-line empirical treatment in NZ: trimethoprim or nitrofurantoin (not in infants under 3 months). Duration: 3-5 days for lower UTI in children over 2 years; 7-10 days for upper UTI or children under 2 years.²

❍ Presentation and investigation

Clinical features vary significantly by age. In infants under 2 years, fever without focus is the most common presentation; other features include irritability, poor feeding, vomiting, and rarely jaundice in neonates. In children aged 2-5 years, abdominal pain, vomiting, and malodorous urine may accompany the fever. In school-age children (over 5 years), the adult pattern of dysuria, frequency, and urgency is more recognisable, with or without fever.¹

A urine specimen should be obtained in any child under 3 years with unexplained fever lasting more than 48 hours, in any child under 5 with fever and no clear source, in any girl under 5 with lower urinary tract symptoms, and in any uncircumcised boy under 1 year with fever.

Distinguish upper UTI (pyelonephritis - fever, rigors, loin pain, high inflammatory markers) from lower UTI (cystitis - dysuria, frequency, no fever or low-grade fever, normal or mildly elevated CRP). Upper UTI in children under 3 months, or upper UTI unresponsive to oral antibiotics, requires IV treatment and secondary care admission.

The quality of the urine specimen is critical. A bag specimen has an unacceptably high false-positive rate and should never be used for culture. A clean-catch specimen (midstream urine collected into a sterile container during spontaneous void) is the minimum acceptable sample for culture in a child who is not toilet trained. Catheter specimen or suprapubic aspirate (SPA) is required when clean-catch is not possible and a reliable culture is essential (e.g., infants under 3 months). SPA is now rarely performed in NZ primary care but remains the gold standard in neonates.

Urine dipstick: a positive nitrite result has high specificity for UTI (>90%); leucocyte esterase alone has lower specificity. A negative dipstick (negative nitrites and negative leucocyte esterase) has a negative predictive value of approximately 97% in children over 3 months. In children under 3 months, send MC&S regardless. MC&S confirms the diagnosis, identifies the organism, and guides antibiotic choice. Common organisms: Escherichia coli (80-90% of cases), Klebsiella, Proteus, Enterococcus.

❍ Management and imaging

Oral antibiotics are appropriate for most children with uncomplicated UTI who can tolerate oral medication. In NZ, first-line empirical choices pending MC&S: trimethoprim (8 mg/kg/day in 2 divided doses, max 300 mg/day) or nitrofurantoin (3 mg/kg/day in 3-4 divided doses, not in infants under 3 months or with eGFR impairment). Amoxicillin-clavulanate is an alternative but E. coli resistance rates are higher. Duration: 3-5 days for lower UTI in children over 2 years; 7-10 days for upper UTI or children under 2 years.² Adjust according to MC&S sensitivity results.

Ensure adequate fluid intake. Constipation is a significant contributing factor to recurrent UTI in children; address it actively if present. Bladder and bowel dysfunction (BBD) is increasingly recognised as a driver of recurrent childhood UTI.

Imaging after a first UTI is guided by age, clinical severity, and response to treatment, following the NICE guidance framework.¹ In NZ practice: children under 6 months with a first UTI, or any child with an atypical or recurrent UTI, are referred for renal ultrasound. Routine DMSA scanning and MCUG are no longer recommended after a first uncomplicated UTI in children over 6 months without atypical features. Discuss with secondary care for children under 6 months or those with recurrent or atypical UTI. Vesicoureteric reflux (VUR) is found in 30-40% of children investigated after UTI; management is determined in secondary care and depends on grade.

❍ Referral criteria

Refer same-day (secondary care admission) for: any infant under 3 months with confirmed or suspected UTI; upper UTI in a child who cannot tolerate oral fluids or antibiotics; suspected septicaemia; failure to respond to 48 hours of appropriate oral antibiotics; upper UTI with significant vomiting precluding oral treatment.

Refer to paediatrics for outpatient review for: first UTI in a child under 6 months; recurrent UTI (two or more episodes of upper UTI, or three or more of lower UTI); any child with atypical UTI features (non-E. coli organism, poor urine flow, abdominal or bladder mass, failure to respond within 48 hours); UTI with known urological abnormality.