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This is a clinician-written, evidence-based summary aligned to the 2026 MLA Content Map. It is intended for medical students and junior doctors preparing for the UKMLA. Always cross-reference with NICE guidance, local protocols, and clinical judgement.
Key points
- UTI affects ~8% of girls and 2% of boys by age 7. More common in uncircumcised boys in first year of life
- Presentation varies with age: neonates/infants — non-specific (fever, poor feeding, irritability, jaundice); older children — dysuria, frequency, abdominal/loin pain
- Urine collection: clean catch is gold standard. If not possible: urine collection pad. Catheter/SPA for sick infants. Do NOT use bag specimens for culture (high contamination)
- Atypical UTI: seriously ill, poor urine flow, abdominal/bladder mass, raised creatinine, septicaemia, failure to respond to antibiotics within 48 h, non-E. coli organism
- Recurrent UTI: 2+ episodes of upper UTI, 1 upper + 1 lower, or 3+ lower UTIs
- Imaging per NICE NG224: USS for all <6 months + atypical/recurrent. DMSA (renal scarring) 4–6 months after infection. MCUG for atypical <6 months or recurrent <6 months
Overview
UTI in children is important because it may be a marker of underlying urinary tract abnormalities and can cause renal scarring, particularly in young children with vesicoureteric reflux (VUR). E. coli is the most common causative organism (~80%). UTI is classified as upper (pyelonephritis/upper — fever, loin pain, systemic features) or lower (cystitis — dysuria, frequency, no systemic features). NICE NG224 provides clear guidance on investigation and imaging based on age, typicality, and recurrence.
Epidemiology
By age 7, approximately 8% of girls and 2% of boys will have had a UTI. In the first year of life, UTIs are more common in boys (particularly uncircumcised). After the first year, UTIs are much more common in girls due to a shorter urethra. Risk factors include vesicoureteric reflux (30–50% of children with UTI), constipation, dysfunctional voiding, incomplete bladder emptying, and structural abnormalities (PUJ obstruction, duplex kidney, posterior urethral valves in boys).
Clinical Features
Symptoms
Infants: fever without focus, poor feeding, vomiting, irritability, lethargy, prolonged jaundice
Older children: dysuria, frequency, urgency, abdominal pain, enuresis (new onset)
Upper UTI/pyelonephritis: high fever (39C+), loin/flank pain, rigors, vomiting
Poor urine stream in boys (think posterior urethral valves)
Failure to respond to antibiotics within 48 hours
Signs
Fever — may be the only finding in infants
Suprapubic or loin tenderness
Palpable bladder or kidneys (structural abnormality)
Signs of sepsis in neonates
Investigations
First-line
Urine dipstickLeucocyte esterase AND nitrite positive = treat as UTI. Nitrite alone = treat. Leucocyte alone = send for MC&S but consider other causes
Urine MC&SGold standard for diagnosis. Clean catch is best method. Significant bacteriuria: >10^5 CFU/mL (clean catch) or >10^4 (catheter/SPA)
Clean catch urinePreferred method in all children. Urine collection pad if unsuccessful. NEVER rely on bag specimens for culture (contamination rate >60%)
Second-line
Renal and bladder USSAll children <6 months with first UTI. Atypical UTI at any age. Recurrent UTI at any age. During acute infection if atypical
DMSA scan4–6 months after acute infection — detects renal scarring. Indicated for atypical or recurrent UTI
Specialist
MCUG (micturating cystourethrogram)Detects vesicoureteric reflux and posterior urethral valves. Indicated for: atypical UTI in <6 months, recurrent UTI in <6 months, dilatation on USS, poor urine flow, non-E. coli UTI, family history of VUR
1
Acute treatment
- Upper UTI/pyelonephritis: oral co-amoxiclav or cefalexin for 7–10 days. IV antibiotics if <3 months, vomiting, or seriously ill
- Lower UTI/cystitis: trimethoprim or nitrofurantoin for 3 days
- Neonates (<28 days): IV antibiotics (follow neonatal sepsis pathway)
- Ensure adequate fluid intake
2
Imaging based on NICE pathway
- All <6 months with first UTI: USS within 6 weeks (during acute infection if atypical)
- Atypical UTI: USS during acute infection + DMSA 4–6 months later
- Recurrent UTI: USS + DMSA. MCUG if <6 months
- Typical first UTI in >6 months: no routine imaging needed
3
Prevention of recurrence
- Treat constipation (very common contributor)
- Encourage regular voiding and adequate fluid intake
- Antibiotic prophylaxis: consider for recurrent UTI with VUR or renal scarring — trimethoprim or nitrofurantoin at night
- Circumcision reduces recurrence risk in boys with recurrent UTI and VUR
Complications
- Renal scarring: Risk highest in young children with VUR and delayed treatment — can lead to hypertension, proteinuria, and CKD
- Urosepsis: Especially neonates and young infants
- Renal abscess: Rare — consider if prolonged fever despite antibiotics
UKMLA Exam Tips
- 1Clean catch urine is gold standard. Bag specimens should NEVER be used for culture (high contamination)
- 2Fever without focus in an infant = always dip the urine
- 3Atypical UTI: seriously ill, poor stream, non-E.coli, failure to respond in 48h, raised creatinine, mass
- 4DMSA is done 4–6 months AFTER infection to look for renal scarring — not acutely
- 5MCUG is for VUR — indicated in <6 months with atypical or recurrent UTI
- 6Posterior urethral valves: think in a boy with bilateral hydronephrosis, poor stream, and recurrent UTI
- 7Constipation is the most common correctable risk factor for recurrent UTI
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regional clinical guidance
Urinary Tract Infection in Children: guidance by region
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