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OverviewAetiologyPathophysiologyClinical features and red flagsInvestigationsDifferential diagnosisManagementComplicationsMonitoring and follow-upSpecial situationsCommon pitfallsQuestionsSources
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Educational draft · awaiting clinical reviewThe full textbook explains uncertainty but does not replace live national or local guidance, specialist advice, or current prescribing information.

Urinary-tract infection by age

Paediatrics and child health · UK scope · Sources checked 27 Aug 2026 · Clinical review pending

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Young infant or septic child

A baby under 3 months with suspected UTI needs urgent paediatric specialist assessment. Shock, impaired consciousness, mottling, prolonged capillary refill, respiratory compromise or rapidly worsening physiology at any age indicates possible sepsis.

Action: Arrange emergency transfer or activate the paediatric sepsis response. Obtain urine, blood cultures and other samples promptly when feasible, but do not delay resuscitation or parenteral antibiotics because urine cannot be collected. Use age-appropriate airway, breathing, circulation, glucose and fluid management and involve paediatrics early.

Overview

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.

UTI is bacterial infection of the urinary tract. Escherichia coli predominates, usually ascending from periurethral flora; non-E. coli organisms are more likely after antibiotics, with instrumentation or structural disease and are an atypical feature in NICE imaging decisions.

Age changes both expression and risk. A non-verbal infant may show only systemic illness, whereas a toilet-trained child can localise dysuria, urgency, suprapubic pain or loin pain. Absence of urinary symptoms therefore does not safely exclude UTI in a febrile infant.

Upper UTI involves renal parenchyma and carries greater sepsis and scarring risk. Lower UTI is confined mainly to the bladder. Fever, rigors, loin tenderness and vomiting shift probability towards pyelonephritis but no single symptom perfectly localises infection.

A diagnosis requires compatible illness plus credible urine evidence. Bag contamination, delayed processing and antibiotics given before sampling can create misleading results. Culture remains the reference test for organism identification and susceptibility, although management begins before the result when risk is significant.

Practice

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Paediatrics and child healthOriginal SBA

Fever in a young infant

A 7-week-old has fever, poor feeding and no clear focus. UTI is suspected. What is the most appropriate next action?

Choose one answer, then submit
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Sources and review status4 sources · checked 27 Aug 2026 · clinical review pending+
Sources

Sources and review status

National guidance is shown before implementation-dependent detail. Typical adult dose examples remain subject to patient factors, contraindications and the live BNF or specialist protocol. Source check completed 27 Aug 2026; clinical approval remains outstanding.

  • NICE NG224 UTI in under 16sAge-specific diagnosis, urine collection and testing, upper versus lower infection, imaging and follow-up.
  • NICE NG109 lower UTI prescribingOral antibiotic choices, age bands, course lengths, renal cautions and review.
  • NICE NG111 pyelonephritis prescribingUpper-UTI antibiotic choices, duration and hospital referral criteria.
  • NICE NG254 suspected sepsis in under 16sRecognition, escalation and immediate management of suspected paediatric sepsis.

Editorial contact: Doctor’s Passport editorial team. Source-check date is separate from clinical approval. Report a content problem · Content changes

Authoring stateComplete draftClinical stateAwaiting reviewJurisdictionUnited Kingdom

Assess severity before focusing on the urine. Record age, temperature, heart and respiratory rates, capillary refill, blood pressure when indicated, hydration, alertness, intake, urine output and paediatric early-warning score.

Ask about previous culture-proven infection, previous antibiotics, antenatal renal abnormalities, urinary stream, constipation, withholding, daytime wetting, sexual activity where developmentally appropriate, safeguarding concerns and family renal history.

Examine hydration and perfusion, abdomen, suprapubic region and loins. Look for a palpable bladder or kidney, spinal or sacral abnormality, abnormal genital anatomy, vulvovaginitis, balanitis and another fever source.

Dipstick interpretation is age dependent. Nitrite is specific but may be negative with frequent voiding or organisms that do not reduce nitrate. Leucocyte esterase indicates pyuria but may accompany inflammation outside bacterial UTI.

Oral treatment is appropriate when a child at least 3 months old is clinically stable, can take and retain medicine, and reliable follow-up exists. Intravenous therapy is indicated by severe illness, inability to tolerate oral medicine or a resistant organism without an oral option.

Prevention means treating bowel and bladder dysfunction, avoiding delayed voiding, maintaining normal fluid intake and securing early sampling during recurrence. Routine post-first-episode prophylaxis exposes children to adverse effects and resistance without a general indication.

Key points

  • 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.

Aetiology

01

Ascending enteric bacteria

Perineal organisms, especially Escherichia coli, enter the urethra and ascend into the bladder and sometimes the kidneys.

02

Urinary stasis

Constipation, infrequent voiding, dysfunctional elimination, neurogenic bladder or obstruction prevents complete emptying and favours bacterial persistence.

03

Structural susceptibility

Vesicoureteric reflux, posterior urethral valves and other congenital urinary anomalies increase recurrence, atypical infection and renal injury risk.

04

Healthcare exposure

Recent antibiotics, catheterisation or urinary surgery changes bacterial flora and increases resistant or non-E. coli infection.

Pathophysiology

  1. 1
    Bladder mucosal inflammation

    Bacterial adherence and local inflammation cause dysuria, urgency, frequency, suprapubic discomfort and sometimes visible blood in affected children.

  2. 2
    Renal ascent

    Organisms reaching the renal pelvis and parenchyma provoke fever, systemic cytokine release, loin pain and potential bacteraemia.

  3. 3
    Infant systemic response

    Immature immunity and limited renal reserve allow rapid dissemination, so poor feeding or temperature instability may precede localisation.

  4. 4
    Scarring after inflammation

    Severe or recurrent pyelonephritis, particularly with abnormal drainage, can leave parenchymal defects associated with later hypertension or proteinuria.

Clinical features and red flags

Young infant phenotype

Seek temperature instability, poor feeding, vomiting, lethargy, irritability, jaundice, apnoea or faltering growth rather than waiting for dysuria.

Older child phenotype

Ask directly about painful or frequent urination, urgency, new wetting, malodorous urine, suprapubic pain, loin pain and haematuria.

Upper tract clues

Fever, rigors, vomiting, systemic illness and loin tenderness increase the likelihood of renal parenchymal infection.

Severity assessment

Document perfusion, hydration, consciousness, urine output and a paediatric early-warning score before deciding community or hospital care.

Atypical features

Identify poor flow, mass, raised creatinine, septicaemia, non-E. coli growth or failure to respond within 48 hours.

Recurrence drivers

Ask about constipation, withholding, weak stream, incomplete emptying, previous imaging, antibiotics and culture susceptibilities.

Red flags requiring action

  • 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.

Investigations

  1. 01
    First-line: correctly collected urineFirst stepFirst line
    Why
    Obtain credible evidence before antibiotics and minimise contamination.
    Interpretation and limitations
    Prefer clean catch; use non-invasive alternatives, catheterisation or ultrasound-guided suprapubic aspiration according to feasibility and urgency.
  2. 02
    Age-specific urine dipstick
    Why
    Guide immediate management in children aged at least 3 months.
    Interpretation and limitations
    Apply NICE combinations of leucocyte esterase and nitrite; isolated leucocytes are less specific, while fresh-sample nitrite supports bacterial infection.
  3. 03
    Reference test: urine culture
    Why
    Identify organism, quantify significant growth and provide susceptibility results.
    Interpretation and limitations
    Interpret with collection method, pyuria, symptoms and prior antibiotics; mixed growth commonly indicates contamination and may need repeat sampling.
  4. 04
    Blood tests for systemic illness
    Why
    Assess inflammation, renal function, electrolytes and bacteraemia when upper UTI, sepsis or dehydration is suspected.
    Interpretation and limitations
    Raised creatinine is an atypical feature; cultures should precede antibiotics when this causes no harmful delay.
  5. 05
    Renal imaging by NICE schedule
    Why
    Detect obstruction, congenital abnormality or parenchymal defects after defined atypical or recurrent infections.
    Interpretation and limitations
    Do not scan every child; age, response within 48 hours, organism and recurrence determine ultrasound, DMSA and MCUG use.

Differential diagnosis

01

Viral febrile illness

Respiratory or gastrointestinal symptoms and a clear alternative focus reduce UTI probability, although coinfection remains possible in an unwell infant.

02

Vulvovaginitis or balanitis

External soreness, discharge or local inflammation can produce dysuria with sterile urine and requires genital examination and hygiene assessment.

03

Appendicitis

Progressive focal abdominal pain, guarding and vomiting may cause urinary leucocytes through adjacent inflammation without primary urinary infection.

04

Diabetes mellitus

Polyuria, polydipsia, weight loss, dehydration or glycosuria suggests hyperglycaemia rather than urinary frequency from infection alone.

05

Renal stone or nephritis

Colicky pain, persistent haematuria, hypertension, oedema or substantial proteinuria directs investigation towards calculus or glomerular disease.

Management

01Under 3 monthsEscalate every suspected infectionFirst stepEscalationA baby younger than 3 months may have UTI.+
  1. 1Refer urgently to paediatric specialist care and assess through the fever and sepsis pathway.
  2. 2Send urine for urgent microscopy and culture and obtain blood investigations as clinically indicated.
  3. 3Start age-appropriate parenteral antibiotics under the neonatal or young-infant protocol without delaying for a difficult specimen.
02At least 3 monthsTest and localiseA stable child has symptoms compatible with UTI.+
  1. 1Collect urine before antibiotics and use the age-specific dipstick strategy.
  2. 2Distinguish likely upper from lower UTI using fever, systemic illness and loin symptoms; send culture whenever NICE criteria apply.
  3. 3Start the relevant oral regimen if clinically stable, then review culture and response within 48 hours.
03Unwell childTreat sepsis and dehydrationThe child has serious-illness features, vomiting or poor perfusion.+
  1. 1Stabilise airway, breathing and circulation, check glucose and obtain cultures when feasible.
  2. 2Give parenteral antibiotics and cautious age-appropriate fluids according to the paediatric sepsis pathway.
  3. 3Monitor urine output and renal function, obtain urgent imaging if obstruction or pyonephrosis is suspected, and involve paediatrics or urology.
04Non-responseReassess at 24 to 48 hoursSymptoms worsen or fail to improve after treatment begins.+
  1. 1Check dose, adherence, vomiting, culture susceptibility and whether the original specimen was credible.
  2. 2Re-examine for obstruction, abscess, stone, appendicitis or another infection and repeat targeted blood or urine tests.
  3. 3EscalationEscalate for paediatric review and image according to atypical-UTI guidance; change antibiotics only on clinical and microbiological grounds.
Key medicines and prescribing safety2 treatments · regimens, roles and cautions+
A first-choice oral option for lower UTI when renal function and susceptibility are suitable.

Nitrofurantoin

Child 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.

An oral option for upper UTI and an alternative for lower infection when indicated.

Cefalexin

For 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.

Complications

01

Urosepsis

Bacteraemia can produce shock and organ dysfunction, especially in young infants or children with underlying urinary obstruction.

02

Renal parenchymal scarring

Upper infection can leave permanent defects, with risk amplified by recurrence, delayed treatment and abnormal urinary anatomy.

03

Renal or perinephric abscess

Persistent fever despite susceptible therapy may reflect focal suppuration requiring imaging, prolonged antibiotics and drainage review.

04

Hypertension and kidney disease

Extensive bilateral scars may later cause proteinuria, reduced filtration, hypertension and pregnancy-related renal risk during adult life.

Monitoring and follow-up

  • Review temperature, pain, hydration, oral intake and urine output; deterioration can precede a culture result.
  • Check the culture and susceptibility result promptly and document whether treatment is continued, narrowed, changed or stopped.
  • Expect clear clinical improvement within 24–48 hours; absence of improvement is an atypical feature requiring reassessment.
  • Monitor creatinine and electrolytes when upper UTI, dehydration, sepsis, nephrotoxic exposure or urinary obstruction is possible.
  • Record organism and collection method so future episodes and imaging decisions are based on confirmed infection.
  • At discharge, teach prompt sampling for recurrence and give explicit advice for fever, vomiting, reduced urine, lethargy or worsening pain.

Special situations

Nitrite needs bladder dwell time

Frequent infant voiding can produce a false-negative nitrite result even with a nitrate-reducing organism.

Age is a management variable

The same nonspecific fever carries a different pathway under 3 months because invasive bacterial infection risk is higher.

Culture quality determines value

A contaminated bag specimen can trigger unnecessary antibiotics and imaging, so collection method must accompany interpretation.

Upper infection changes duration

Pyelonephritis needs the longer NICE regimen; a three-day cystitis course is not adequate for renal parenchymal infection.

Constipation is clinically relevant

Rectal loading can impair bladder emptying, reinforce withholding and drive recurrent urinary symptoms and infection.

Common pitfalls

  1. 01

    Do not wait for dysuria before considering UTI in an infant with unexplained fever or poor feeding.

  2. 02

    Do not manage a baby under 3 months with suspected UTI solely in the community.

  3. 03

    Do not postpone sepsis antibiotics while repeatedly attempting urine collection in a seriously ill child.

  4. 04

    Do not call mixed growth from a poorly collected specimen definitive infection without clinical correlation.

  5. 05

    Do not treat isolated leucocyte esterase in an older child automatically when symptoms do not support UTI.

  6. 06

    Do not use a short lower-UTI course for febrile pyelonephritis.

  7. 07

    Do not ignore constipation, weak stream or recurrent wetting when evaluating recurrence.

  8. 08

    Do not prescribe routine antibiotic prophylaxis after a single uncomplicated infection.