Urinary-tract infection by age — Rapid

Synopsis

Recognise urinary-tract infection despite age-dependent presentations, separate lower from upper infection, obtain a valid specimen without delaying treatment of a seriously ill child, and select safe antimicrobial and escalation pathways.

Presentation changes with age: young infants may have fever, hypothermia, poor feeding, vomiting, lethargy, irritability, jaundice or faltering growth without urinary symptoms.
Older children more often report dysuria, frequency, urgency, new wetting, malodorous or cloudy urine, suprapubic pain, abdominal pain or visible haematuria.
Refer every baby under 3 months with suspected UTI for paediatric specialist care; send urine for urgent microscopy and culture and follow the fever or sepsis pathway.
First-line sampling is clean catch before antibiotics. Use another non-invasive method if necessary, then catheterisation or ultrasound-guided suprapubic aspiration when a reliable specimen cannot otherwise be obtained.
Do not delay antibiotics in a baby or child at high risk of serious illness merely because a urine specimen is difficult to obtain.
From 3 months to under 3 years, both leucocyte esterase and nitrite negative usually excludes UTI; either positive requires culture and antibiotics under NICE NG224.
At age 3 years or more, nitrite positivity supports immediate antibiotics; isolated leucocyte esterase requires culture and treatment only when the clinical evidence is convincing.
Send culture for suspected upper UTI, age under 3 months, recurrent UTI, serious illness, any positive leucocyte esterase or nitrite, non-response within 24–48 hours, or discordant symptoms and dipstick.
Assume upper UTI when bacteriuria accompanies fever of at least 38°C, or when fever is lower but loin pain or tenderness is present. Bacteriuria without systemic features is lower UTI.
First-line treatment for an otherwise well child at least 3 months old is oral, selected from the relevant NICE lower-UTI or pyelonephritis table using culture history, renal function and local resistance data.
Review culture and susceptibility when available: narrow, change or stop therapy when the microbiology and clinical diagnosis require it, and reassess any child not improving within 48 hours.
Do not routinely prescribe prophylactic antibiotics after a first UTI. Address constipation, dysfunctional voiding, adequate fluids and prompt access to testing for recurrence.

Key red flags

Age under 3 months with suspected UTI requires urgent paediatric referral, urgent urine microscopy and culture, and management through the fever or neonatal sepsis pathway.

Shock, altered responsiveness, cyanosis, grunting, marked tachypnoea, prolonged capillary refill or a deteriorating paediatric early-warning score requires emergency sepsis care.

Poor urine flow, a palpable abdominal or bladder mass, raised creatinine, septicaemia, non-E. coli infection or failure to improve within 48 hours defines an atypical UTI feature.

Fever with loin pain or tenderness, rigors, vomiting or systemic illness suggests upper UTI and requires a longer pyelonephritis regimen and culture.

Dehydration, persistent vomiting, inability to take oral antibiotics or concern about adherence lowers the threshold for hospital assessment and intravenous treatment.

Recurrent upper or lower infections, hypertension, impaired growth, proteinuria or abnormal imaging requires specialist assessment for renal damage or urinary-tract abnormality.

Investigation priorities

First-line: correctly collected urineFirst stepFirst line

Obtain credible evidence before antibiotics and minimise contamination.

Management branches

Under 3 monthsEscalate every suspected infection

A baby younger than 3 months may have UTI.

Refer urgently to paediatric specialist care and assess through the fever and sepsis pathway.
Send urine for urgent microscopy and culture and obtain blood investigations as clinically indicated.
Start age-appropriate parenteral antibiotics under the neonatal or young-infant protocol without delaying for a difficult specimen.

At least 3 monthsTest and localise

A stable child has symptoms compatible with UTI.

Collect urine before antibiotics and use the age-specific dipstick strategy.
Distinguish likely upper from lower UTI using fever, systemic illness and loin symptoms; send culture whenever NICE criteria apply.
Start the relevant oral regimen if clinically stable, then review culture and response within 48 hours.

Key medicines

NitrofurantoinChild aged 3 months to 11 years with uncomplicated lower UTI: 750 micrograms/kg orally four times daily for 3 days; age 12 to 15 years: 50 mg orally four times daily or 100 mg modified release twice daily for 3 days, following the current NICE table.Do not use for pyelonephritis because renal-tissue concentrations are inadequate. Check eGFR, age, formulation and G6PD status where relevant; review pulmonary or hepatic symptoms and local resistance advice.

CefalexinFor acute pyelonephritis from age 3 months, use the current NICE age or weight band orally for 7 to 10 days; a commonly used child dose is 12.5 mg/kg twice daily, with higher dosing only for severe infection under paediatric advice.Verify the current BNFC maximum, allergy history, renal function, severity and culture susceptibility. Admit for intravenous therapy if septic, vomiting, unable to absorb medicine or lacking a susceptible oral option.

Open full textbook →Answer 2 questions