Urinary tract infection - children
Exam Tips
- In any unwell child with unexplained fever >=38 C, think UTI and obtain urine early; fever + bacteriuria or loin tenderness indicates upper UTI.
- Children <3 months with suspected UTI need same-day paediatric referral and parenteral antibiotics after urine sampling where possible.
- Atypical UTI red flags: serious illness, poor urine flow, abdominal/bladder mass, raised creatinine, sepsis, non-E. coli organism, or failure to improve within 48 hours.
- Recurrent UTI definitions are exam favorites: >=2 upper UTIs, or 1 upper plus >=1 lower, or >=3 lower UTIs.
- Do not use nitrofurantoin for pyelonephritis; it is suitable for lower UTI only.
- Always ask about bowel and bladder dysfunction (constipation, withholding, poor stream), because treating these reduces recurrence.
Definition
Paediatric urinary tract infection (UTI) is microbial infection of the urinary tract in children under 16 years, confirmed by bacteriuria on appropriately collected urine testing with compatible clinical features. It is classified into lower UTI (cystitis: bladder/urethra) and upper UTI (acute pyelonephritis: renal pelvis/kidney), with atypical and recurrent patterns used to identify children at higher risk of structural disease, renal injury, or treatment failure.
Pathophysiology
Most childhood UTIs are ascending infections from peri-urethral enteric flora, most commonly Escherichia coli (about 85-90%), with bacterial adherence to uroepithelium (fimbriae-mediated) followed by bladder colonisation and inflammation. Upper tract disease occurs when organisms ascend to the kidney, provoking interstitial inflammation that can cause parenchymal injury; risk is amplified by vesicoureteric reflux (VUR), urinary stasis, obstruction, and dysfunctional voiding/constipation. Repeated febrile UTIs, especially with high-grade VUR, increase risk of renal scarring and later sequelae (hypertension, CKD). Non-E. coli organisms (e. g, Proteus, Pseudomonas, Enterococcus, Klebsiella) are more suggestive of atypical infection or urinary tract abnormality. See Figure: ascending infection and reflux-related renal scarring pathway (standard paediatric nephrology schematic).
Risk Factors
- Age under 1 year (boys predominate in first 3 months; girls thereafter)
- Female sex (after early infancy)
- Uncircumcised infant boys (markedly higher incidence in first year)
- Previous UTI (high recurrence risk)
- Vesicoureteric reflux (VUR), family history of VUR or renal disease
- Voiding dysfunction, infrequent voiding, dysfunctional elimination
- Chronic constipation
- Urinary tract structural abnormalities or neurogenic bladder
- Sexual activity in adolescent girls
- No breastfeeding history
- Immunosuppression
Clinical Features
Symptoms
- Fever (often unexplained, especially >=38 C)
- Dysuria
- Urinary frequency/urgency
- New incontinence or secondary enuresis
- Abdominal pain or suprapubic pain
- Loin/flank pain
- Vomiting
- Poor feeding, lethargy, irritability (especially infants)
- Offensive/cloudy/darker urine
- Haematuria
Signs
- Temperature >=38 C (suggests upper UTI if bacteriuria present)
- Loin tenderness or renal angle tenderness
- Suprapubic tenderness
- Delayed capillary refill (>3 seconds) or other red flags of serious illness/sepsis
- Poor growth/failure to thrive
- Hypertension (suggesting possible renal involvement)
- Palpable abdominal/bladder mass (atypical feature)
- Features suggesting alternative focus (abnormal chest or ear exam) reduce likelihood of UTI
Investigations
Management
Lifestyle Modifications
- Encourage adequate hydration and regular timed voiding.
- Treat constipation and dysfunctional elimination to reduce recurrence risk.
- Provide safety-net advice: seek urgent review for persistent fever, vomiting, reduced urine output, lethargy, or no improvement within 48 hours.
- Perineal hygiene advice and avoidance of irritants; address adolescent sexual-health factors sensitively.
- Do not delay treatment in a high-risk unwell child if urine cannot be obtained immediately.
Pharmacological Treatment
Oral antibiotics for lower UTI (typically 3 days in children >=3 months if not systemically unwell)
- Trimethoprim: 4 mg/kg twice daily (max 200 mg per dose)
- Nitrofurantoin: 750 micrograms/kg four times daily (max 50 mg per dose) or modified-release 1 mg/kg twice daily (max 100 mg per dose)
- Cefalexin: 12.5 mg/kg three times daily (max 500 mg per dose)
Choose using local resistance and culture history; send culture when indicated. Avoid nitrofurantoin if eGFR <45 mL/min/1.73 m2, suspected pyelonephritis, or G6PD deficiency risk. Check beta-lactam allergy before cefalexin.
Oral antibiotics for upper UTI/pyelonephritis (usually 7-10 days)
- Co-amoxiclav: 30 mg/kg (amoxicillin component) three times daily (max 500 mg amoxicillin per dose)
- Cefalexin: 12.5 mg/kg three times daily (max 500 mg per dose)
- Trimethoprim: 4 mg/kg twice daily (max 200 mg per dose), if susceptible
Use culture/sensitivity to step down or switch. Avoid nitrofurantoin for pyelonephritis (poor tissue penetration). Co-amoxiclav caution in prior cholestatic jaundice/liver dysfunction associated with penicillins.
Parenteral therapy for infants <3 months or severe illness/poor oral tolerance
- Cefotaxime: 50 mg/kg IV every 6-8 hours
- Ceftriaxone: 50 mg/kg IV once daily (typically avoid in neonates with hyperbilirubinaemia)
- Gentamicin: 7 mg/kg IV once daily (age-adjusted protocols)
Urgent paediatric referral required. Monitor renal function and drug levels where required (especially aminoglycosides). Watch for sepsis and complications; convert to oral when clinically improved and cultures available.
Antibiotic prophylaxis for recurrent UTI (specialist-led, selected cases)
- Trimethoprim: 1-2 mg/kg at night
- Nitrofurantoin: 1 mg/kg at night
- Cefalexin: 12.5 mg/kg at night
Reserved for recurrent/febrile UTIs or specific urological risk after specialist review. Reassess regularly to limit resistance and adverse effects.
Symptom control
- Paracetamol: 15 mg/kg every 4-6 hours (max 4 doses/24 h)
- Ibuprofen: 5-10 mg/kg every 6-8 hours (max 30 mg/kg/day)
Use antipyretics for distress. Avoid NSAIDs in dehydration/AKI risk. Encourage fluids.
Surgical / Interventional
- No routine surgery for uncomplicated first UTI.
- Investigate and correct underlying obstructive lesions (e. g, posterior urethral valves) where present.
- Selected high-grade persistent VUR with breakthrough infections despite optimal medical management may require endoscopic injection or ureteric reimplantation under paediatric urology.
Complications
- Renal parenchymal scarring (more likely after febrile upper UTI and with high-grade VUR)
- Recurrent UTIs
- Sepsis (especially in young infants)
- Hypertension later in life (mainly with significant bilateral scarring)
- Chronic kidney disease/rare progression to kidney failure in severe bilateral damage
- Adverse pregnancy outcomes in later life in those with significant renal scarring (e. g, hypertensive disorders, bacteriuria risk)
Prognosis
Overall prognosis is good for most children, particularly with prompt diagnosis and treatment. Recurrence is common (higher in girls and in those infected in infancy, VUR, or voiding dysfunction), while serious long-term renal outcomes are uncommon and largely concentrated in children with recurrent febrile infection and substantial bilateral renal scarring.
Sources & References
🏥BMJ Best Practice(2)
💊BNF Drug References(9)
- Amoxicillin[management.pharmacological]
- Botulinum toxin type A[contraindications]
- Cefalexin[management.pharmacological]
- Estradiol[management.pharmacological]
- Estriol[management.pharmacological]
- Nitrofurantoin[management.pharmacological]
- Tiaprofenic acid[contraindications]
- Tobramycin[management.pharmacological]
- Trimethoprim[management.pharmacological]
✅NICE Guidelines(1)
- Urinary tract infection - children[overview]
📖Textbook References(20)
- David Randall PhD MRCP (Editor), John Booth PhD MRCP (Editor), K - Kumar and Clark's Clinical Medicine (2025, American Elsevier Publishing Co.) - libgen.li.pdf(pp. 1772)[context]
- David Randall PhD MRCP (Editor), John Booth PhD MRCP (Editor), K - Kumar and Clark's Clinical Medicine (2025, American Elsevier Publishing Co.) - libgen.li.pdf(pp. 1772)[context]
- David Randall PhD MRCP (Editor), John Booth PhD MRCP (Editor), K - Kumar and Clark's Clinical Medicine (2025, American Elsevier Publishing Co.) - libgen.li.pdf(pp. 871, 872)[context]
- David Randall PhD MRCP (Editor), John Booth PhD MRCP (Editor), K - Kumar and Clark's Clinical Medicine (2025, American Elsevier Publishing Co.) - libgen.li.pdf(pp. 1845)[context]
- David Randall PhD MRCP (Editor), John Booth PhD MRCP (Editor), K - Kumar and Clark's Clinical Medicine (2025, American Elsevier Publishing Co.) - libgen.li.pdf(pp. 1802, 1803)[context]
- David Randall PhD MRCP (Editor), John Booth PhD MRCP (Editor), K - Kumar and Clark's Clinical Medicine (2025, American Elsevier Publishing Co.) - libgen.li.pdf(pp. 830)[context]
- David Randall PhD MRCP (Editor), John Booth PhD MRCP (Editor), K - Kumar and Clark's Clinical Medicine (2025, American Elsevier Publishing Co.) - libgen.li.pdf(pp. 1472, 1473)[context]
- David Randall PhD MRCP (Editor), John Booth PhD MRCP (Editor), K - Kumar and Clark's Clinical Medicine (2025, American Elsevier Publishing Co.) - libgen.li.pdf(pp. 1802)[context]
- David Randall PhD MRCP (Editor), John Booth PhD MRCP (Editor), K - Kumar and Clark's Clinical Medicine (2025, American Elsevier Publishing Co.) - libgen.li.pdf(pp. 39)[context]
- Emergencies in - Obstetrics and Gynaecology, Second Edition (Stergios K. Doumouchtsis, S. Arulkumaran) (Z-Library).pdf(pp. 264, 265)[context]
- Emergencies in - Obstetrics and Gynaecology, Second Edition (Stergios K. Doumouchtsis, S. Arulkumaran) (Z-Library).pdf(pp. 205)[context]
- Emergencies in - Obstetrics and Gynaecology, Second Edition (Stergios K. Doumouchtsis, S. Arulkumaran) (Z-Library).pdf(pp. 262, 263)[context]
- Oxford Handbook of Clinical Diagnosis (Huw Llewelyn, Hock Aun Ang, Keir Lewis etc.) (Z-Library).pdf(pp. 416, 417)[context]
- [Williams, Bailey and Love's Short Practice of Surgery] Norman Williams, Christopher Bulstrode, P Ronan O'Connell - Bailey & Love's Short Practice of Surgery 26E (2013, CRC Press) - libgen.li.pdf(pp. 1339)[context]
- [Williams, Bailey and Love's Short Practice of Surgery] Norman Williams, Christopher Bulstrode, P Ronan O'Connell - Bailey & Love's Short Practice of Surgery 26E (2013, CRC Press) - libgen.li.pdf(pp. 1187, 1188)[context]
- [Williams, Bailey and Love's Short Practice of Surgery] Norman Williams, Christopher Bulstrode, P Ronan O'Connell - Bailey & Love's Short Practice of Surgery 26E (2013, CRC Press) - libgen.li.pdf(pp. 1343)[context]
- [Williams, Bailey and Love's Short Practice of Surgery] Norman Williams, Christopher Bulstrode, P Ronan O'Connell - Bailey & Love's Short Practice of Surgery 26E (2013, CRC Press) - libgen.li.pdf(pp. 1386)[context]
- [Williams, Bailey and Love's Short Practice of Surgery] Norman Williams, Christopher Bulstrode, P Ronan O'Connell - Bailey & Love's Short Practice of Surgery 26E (2013, CRC Press) - libgen.li.pdf(pp. 140, 141)[context]
- [Williams, Bailey and Love's Short Practice of Surgery] Norman Williams, Christopher Bulstrode, P Ronan O'Connell - Bailey & Love's Short Practice of Surgery 26E (2013, CRC Press) - libgen.li.pdf(pp. 1444)[context]
- [Williams, Bailey and Love's Short Practice of Surgery] Norman Williams, Christopher Bulstrode, P Ronan O'Connell - Bailey & Love's Short Practice of Surgery 26E (2013, CRC Press) - libgen.li.pdf(pp. 129)[context]