Urinary Tract Infection (UTI) – Children

• Bacteriuria with no systemic features.

• Bacteriuria plus fever ≥38°C, or fever <38°C with loin pain/tenderness.

• Dysuria, frequency, urgency, suprapubic or abdominal pain, new daytime wetting, cloudy or offensive urine.

• Systemically unwell – high fever, rigors, vomiting, loin pain.

• Oral antibiotics for 3 days.

• Antibiotics for 7–10 days; consider paediatric referral.

• Infant <3 months – fever, vomiting, poor feeding, lethargy, irritability or jaundice (non-specific)?

• Any previous confirmed UTI, and how many episodes?

• Child >3 months – dysuria, frequency, urgency, abdominal or loin pain?

• Constipation and dysfunctional voiding (infrequent or incomplete emptying) – the major modifiable risk factors?

• New daytime wetting or secondary bedwetting in a previously dry child?

• Poor or interrupted urinary stream (possible obstruction)?

• Cloudy, dark or offensive urine, or visible haematuria?

• Antenatally diagnosed renal abnormality, known vesicoureteric reflux (VUR) or other uropathy?

• Is the child systemically unwell – high fever, rigors, repeated vomiting (suggests upper UTI or sepsis)?

• Family history of VUR or renal disease?

• In recurrent cases, the pattern and number of previous episodes (upper vs lower)?

• Poor growth, recurrent unexplained fevers, or high blood pressure (markers of underlying pathology)?

➤ “How is your child in themselves – feeding and drinking normally, and behaving like their usual self?”

➤ “What are you most worried about? Many parents fear long-term kidney damage – explore those concerns and what they expect from tests and treatment.”

➤ Infant <3 months with a suspected UTI or fever ≥38°C → immediate paediatric referral + urgent microscopy and culture.

➤ Suspected sepsis (mottled or ashen skin, altered responsiveness, tachycardia, poor perfusion) → emergency admission; manage per sepsis guidance.

➤ Acute upper UTI / pyelonephritis (bacteriuria + fever ≥38°C, rigors, loin pain, vomiting) → treat without delay; consider paediatric referral.

➤ Atypical UTI (seriously ill, poor urine flow, abdominal or bladder mass, raised creatinine, septicaemia, non-E. coli organism) → urgent paediatric assessment + ultrasound during the acute infection.

➤ Palpable abdominal or bladder mass, or poor urine flow → possible obstruction → urgent paediatric referral.

➤ Failure to respond to an appropriate antibiotic within 48 hours → reassess, check or send culture, and refer.

• Vitals and sepsis screen – temperature, heart rate, respiratory rate, capillary refill and conscious level; cross-check against the traffic-light system for the febrile under-5 and escalate if features of serious illness.

• Hydration – mucous membranes, skin turgor, urine output and, in infants, the fontanelle.

• Abdomen – suprapubic tenderness, a palpable distended bladder (retention), or an abdominal/flank mass.

• Loin / renal-angle tenderness in older children – supports an upper UTI.

• Blood pressure (appropriately sized cuff) and plot growth – markers of underlying renal pathology.

• Genitalia – in boys, phimosis or structural abnormality; in girls, vulvovaginitis; consider threadworm.

• Lower spine – a sacral dimple, hairy patch or other sign of spinal dysraphism and a neuropathic bladder.

⚠️ Common pitfall

Dysuria is not always a UTI. In young girls, vulvovaginitis (often from bubble baths or strong soaps), and in any child threadworm or constipation, can cause dysuria, frequency and urgency with a negative culture. Examine the genitalia and ask about bowels before committing a child to a UTI label and antibiotics on symptoms alone.

A urine infection (UTI) means germs have got into your child’s wee, and it usually settles quickly with a short course of antibiotics. It is important to finish the whole course, even once your child feels better, and to come back if they are not improving within two days. At home, the things that help most are plenty of fluids, regular trips to the toilet, and keeping the bowels soft.

Urine dipstick (leukocyte esterase + nitrite)

First test in children 3 months to under 3 years and 3 years or older; both negative makes UTI unlikely in these groups. Do not use a dipstick to rule out UTI in babies under 3 months.

Urine microscopy & culture (clean-catch MC&S)

Obtain before antibiotics. Send for babies under 3 months (urgent), and when the dipstick is positive, an upper UTI is suspected, the UTI is recurrent or atypical, there is intermediate/high risk of serious illness, or there is no response within 48 hours.

Renal tract ultrasound

During the acute infection for an atypical UTI; within 6 weeks for babies under 6 months with a first UTI, and for recurrent UTI – following the age-based schedule.

DMSA scintigraphy – specialist-initiated

Performed 4–6 months after the acute infection to detect renal scarring, per the age and atypical/recurrent criteria.

MCUG (micturating cystourethrogram) – specialist-initiated

To assess vesicoureteric reflux in selected cases (e.g. under 6 months, dilatation on ultrasound, poor urine flow, non-E. coli infection, or family history of VUR). Give prophylactic antibiotic cover around the procedure.

🧠 Clinical pearl

A fever of 38°C or higher with bacteriuria is an upper UTI by definition – treat for 7–10 days, not 3, even when there is no loin pain. And do not reach for nitrofurantoin in that situation: it concentrates in urine but not in kidney tissue, so it does not treat pyelonephritis.

• Send a clean-catch MC&S before antibiotics wherever culture is indicated.

• Any infant <3 months → immediate paediatric referral for same-day assessment and parenteral antibiotics.

• Lower UTI (≥3 months) → oral antibiotics for 3 days.

• Suspected sepsis or high risk of serious illness → emergency admission.

• Upper UTI (≥3 months) → oral antibiotics for 7–10 days; consider paediatric referral.

• Unable to tolerate oral antibiotics, dehydrated, or severely unwell → admit for IV antibiotics.

• Encourage fluids; identify and treat constipation and dysfunctional voiding; offer paracetamol for pain and fever.

• No response within 48 hours → reassess, check or send culture, and refer.

• Do not treat asymptomatic bacteriuria; do not start prophylaxis after a first UTI.

• Atypical features (mass, poor flow, raised creatinine, non-E. coli) → urgent paediatric assessment + ultrasound during the acute infection.

• Image per age and atypical/recurrent criteria; a detected abnormality must never be lost to follow-up.

🔑 Key principle – treat the child, find the cause, prevent the next one

Most childhood UTIs resolve with a short antibiotic course. The lasting work is twofold: spot the minority with an underlying abnormality by imaging according to the age and atypical/recurrent rules, and relentlessly treat constipation and dysfunctional voiding – the commonest modifiable drivers of recurrence. A clean-catch culture sent before the first dose is the single highest-value action, steering therapy when roughly a third of urinary E. coli are now resistant to trimethoprim. Prophylactic antibiotics are not started in primary care after a single UTI.

Hydration

Encourage regular fluids to maintain a good urine output and flush the urinary tract.

Complete & regular voiding

Avoid “holding on”; encourage a regular toileting routine and double voiding (passing urine again a moment later) where incomplete emptying is suspected.

Constipation

Identify and actively treat – the commonest modifiable driver of recurrence and incomplete bladder emptying.

Hygiene

In girls, wipe front to back; avoid bubble baths and strong soaps if they cause irritation.

Toilet access

Ensure unhurried access to clean toilets at nursery or school so voiding is not delayed.

➤ Lower UTI (cystitis) – child 3 months and over · 3-day oral course

→ First-line: Trimethoprim (if low risk of resistance) or Nitrofurantoin (if eGFR ≥45). Representative doses: trimethoprim 4 mg/kg (max 200 mg/dose) twice daily; nitrofurantoin 750 micrograms/kg four times daily – dose by age and weight per BNFc.
→ Trimethoprim is a folate antagonist and teratogenic, so take a pregnancy history in adolescent girls; check local resistance.

→ Second-line (no improvement at 48 h, or first-line unsuitable): Nitrofurantoin (if not used first-line), Amoxicillin (Amoxil® – only if culture confirms susceptibility, as ≈50% of E. coli are resistant) or Cefalexin (Keflex®). Always review against the culture result.

➤ Upper UTI (acute pyelonephritis) – child 3 months and over · 7–10 day oral course (if not admitted)

→ First-line: Cefalexin (Keflex®; e.g. 12.5 mg/kg twice daily, higher in severe infection) – a first-generation cephalosporin with ≈10% E. coli resistance; the pragmatic oral choice when the kidney is involved.

→ Alternative: Co-amoxiclav (Augmentin®) – only if culture confirms susceptibility (≈20% resistant); warn about cholestatic jaundice / hepatotoxicity, particularly with repeated or prolonged courses.

→ Penicillin allergy: Ciprofloxacin (Ciproxin®) – a fluoroquinolone; reserve and counsel per the MHRA restrictions (tendon, musculoskeletal and aortic cautions).

→ Not for upper UTI: Nitrofurantoin – it does not reach therapeutic levels in renal tissue.
→ If vomiting, unable to take oral, or severely unwell → IV antibiotics (co-amoxiclav, cefuroxime, ceftriaxone or gentamicin) in hospital, stepping down to oral to complete the course.

➤ Infant under 3 months – specialist

→ Immediate paediatric referral; treat with parenteral antibiotics in line with the fever-in-under-5s guidance – not a primary-care prescription.

➤ Symptom relief and prophylaxis

→ Paracetamol (e.g. Calpol®) for pain and fever, or ibuprofen (e.g. Nurofen®) if suitable; maintain fluids.
→ Antibiotic prophylaxis is not routine after a single UTI and is specialist-initiated for selected recurrent cases – a single night-time dose of a different agent from the one used to treat the acute episode.

➤ Key prescribing warnings

→ Nitrofurantoin (Macrodantin®; Macrobid® MR for those ≥12 years who can swallow capsules) – contraindicated under 3 months; needs eGFR ≥45; avoid in pyelonephritis; avoid near term (neonatal haemolysis); caution in G6PD deficiency; MHRA warns of pulmonary and hepatic reactions with prolonged use.
→ Trimethoprim – folate antagonist with rising resistance (check local sensitivities); avoid in the first trimester in adolescents.
→ Co-amoxiclav / cefalexin – reserve broad-spectrum agents for upper UTI or per sensitivities; counsel on diarrhoea and nausea.

🧠 Clinical pearl

Nitrofurantoin works only where it concentrates: the urine. It reaches negligible levels in the renal parenchyma and bloodstream, so it is excellent for cystitis but ineffective and unsafe to rely on in pyelonephritis or any systemically unwell child. When the kidney is involved, reach for cefalexin.

• Two or more episodes of upper UTI (acute pyelonephritis).

• One episode of upper UTI plus one or more episodes of lower UTI (cystitis).

• Three or more episodes of lower UTI (cystitis).

• Referral – refer to a paediatrician.

• Referral – refer to a paediatrician or paediatric nephrologist.

• Ultrasound – should already have been performed in the first episode (within 6 weeks); arrange it now if it was not.

• Ultrasound – indicated if not done previously, within 6 weeks of the acute infection settling.

• Further imaging – specialist assessment for DMSA (scarring) and MCUG (reflux) to exclude significant reflux or renal scarring.

• Further imaging – DMSA (scarring) is specialist-requested; MCUG is reserved for selected cases (suspected obstruction or significant reflux).

🔑 Key principle – prophylaxis is a specialist decision, prevention is yours

Do not routinely start antibiotic prophylaxis in primary care, and never after a single UTI. Where a specialist initiates it, it is a single night-time dose of trimethoprim or nitrofurantoin – deliberately a different agent from the one used to treat the acute episode. Meanwhile the highest-value action you can take is to find and treat constipation, the commonest reversible driver of recurrence, alongside good fluids, regular voiding and front-to-back hygiene (see Non-pharmacological Treatment).

📌 Stay safeguarding-aware

• Persistent or unexplained ano-genital symptoms or signs in a child should prompt you to consider sexual abuse, as flagged by NICE in the child-maltreatment guidance – alongside the commoner benign causes (vulvovaginitis, threadworm, irritants).

• Take a careful history, document findings clearly, do not collude with secrecy, and follow your local safeguarding procedures if you are concerned.

• Infant <3 months with suspected UTI → immediate paediatric referral for same-day assessment + urgent microscopy and culture.

• Recurrent UTI (any age) → paediatric specialist for investigation (ultrasound ± DMSA / MCUG).

• Suspected sepsis or high risk of serious illness → emergency admission.

• Ultrasound within 6 weeks for babies under 6 months with a first UTI, and for recurrent UTI per the age schedule.

• Atypical UTI (mass, poor flow, raised creatinine, non-E. coli, no response within 48 hours) → urgent paediatric assessment + ultrasound during the acute infection.

• Abnormal imaging → paediatric specialist; bilateral defects, impaired function, hypertension or proteinuria → paediatric nephrology.

• Unable to tolerate oral antibiotics or dehydrated → admit for IV antibiotics.

• DMSA / MCUG → specialist-initiated in selected cases.

🧭 AKT – high-yield facts

• Under 3 months with suspected UTI → immediate paediatric referral + urgent microscopy and culture; dipstick is not used to rule out.

• Upper UTI = bacteriuria + fever ≥38°C (or fever <38°C + loin pain) → 7–10 days. Lower UTI = 3 days.

• Lower UTI first-line: trimethoprim or nitrofurantoin. Upper UTI: cefalexin (co-amoxiclav only if culture-susceptible). Nitrofurantoin does not treat pyelonephritis (no renal tissue penetration).

• England E. coli resistance: trimethoprim ≈30%, co-amoxiclav ≈20%, cefalexin / ciprofloxacin ≈10% – hence trimethoprim and co-amoxiclav are culture-dependent.

• Nitrofurantoin: contraindicated <3 months; avoid eGFR <45; caution in G6PD deficiency.

• Recurrent UTI = ≥2 upper; or 1 upper + ≥1 lower; or ≥3 lower.

• Atypical UTI = seriously ill, poor flow, abdominal/bladder mass, raised creatinine, septicaemia, non-E. coli, or no response within 48 hours.

• Imaging: ultrasound for all <6 months first UTI, atypical (acute), or recurrent; DMSA/MCUG specialist-initiated.

• Do not treat asymptomatic bacteriuria; prophylaxis is not routine after a single UTI – specialist-initiated (trimethoprim or nitrofurantoin nocte).

🎯 SCA – consultation case

A 3-year-old girl attends with her mother for her third confirmed lower UTI in a year. The mother is very worried about long-term kidney damage and asks for “a daily antibiotic to stop them” and “every scan available”. The child has a long history of hard, infrequent stools. The challenge is to honour the mother’s understandable anxiety and her specific requests while delivering proportionate, guideline-based care: this meets the threshold for recurrent UTI and warrants referral and ultrasound, but routine prophylaxis is specialist-led and not started in primary care, and the likely key driver – constipation – needs a tactful conversation rather than reassurance that dismisses her fears.

A strong consultation explores her ideas, concerns and expectations (fear of kidney damage, any guilt, expectations about antibiotics and scans); explains the recurrent-UTI pathway and the constipation link in plain language without minimising her worry; agrees a shared plan – treat the current infection with a pre-treatment MC&S, refer to paediatrics, arrange an ultrasound, and start a regular toileting routine with a laxative, explaining why daily antibiotics are not begun in primary care; and provides clear safety-netting for fever, systemic illness or failure to improve – all with empathy and respect for the family’s autonomy.