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Urinary Tract Infection (UTI) in the Paediatric Age Group

Comprehensive Notes for INICET / NEETPG

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1. Epidemiology and Significance

• One of the most common serious bacterial infections in children (after respiratory and ear infections)
• Cumulative incidence by age 7 years: ~8% in girls, ~2% in boys
• In febrile infants <3 months: UTI is the most common serious bacterial infection
• Uncircumcised males have 5-10x higher risk in the first year of life than circumcised males (important MCQ point)
• Risk is higher in girls after the first year of life due to shorter urethra
• E. coli accounts for >70% of cases (most common causative organism - high yield)
• Other organisms: Klebsiella, Proteus (associated with struvite stones; more common in boys), Pseudomonas, Enterococcus, Staphylococcus saprophyticus (adolescent girls)

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2. Classification (High Yield for MCQs)

• APN (Pyelonephritis) = fever + systemic symptoms; more likely in infants; risk of renal scarring
• Cystitis = lower tract symptoms (dysuria, frequency, urgency) without fever; negligible risk of scarring

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3. Clinical Features

Neonates and Young Infants (<3 months)

• Non-specific: fever, poor feeding, vomiting, irritability, jaundice (in neonates), failure to thrive, sepsis
• No localising urinary symptoms

Infants (3 months - 2 years)

• Fever without source is the classic presentation - must rule out UTI
• Vomiting, diarrhoea, poor weight gain, crying during micturition
• Risk of urosepsis

Children >2 years

• Cystitis symptoms: dysuria, frequency, urgency, enuresis, suprapubic pain
• APN symptoms: fever, rigors, flank/loin pain, costovertebral angle tenderness, vomiting

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4. Diagnosis

A. Urine Collection (Critically Important - MCQ!)

• For pre-toilet trained children: catheterisation or SPA is preferred
• For toilet-trained children: clean midstream catch is acceptable

ISPN 2024 update: Culture >10⁴ CFU/mL in an infant is considered significant if clinical suspicion is strong (lowered threshold)

B. Urinalysis (Dipstick / Microscopy)

• Positive dipstick (LE and/or nitrite) = send urine culture before starting antibiotics
• IAP STG 2022: LE + nitrite can replace microscopy as a screening tool

C. Urine Culture (Gold Standard)

• Must be sent before starting antibiotics
• Single species growth + clinical symptoms = UTI
• Polymicrobial growth = likely contamination

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5. Investigations After UTI

Renal Bladder Ultrasonography (RBUS / USG KUB)

• Indicated in ALL children with febrile UTI (first episode)
• Identifies: hydronephrosis, renal anomalies, bladder abnormalities, calculi
• ISPN 2024: RBUS should be done in all children with febrile UTI

Micturating Cystourethrography (MCUG / VCUG)

• Recurrent febrile UTI (≥2 episodes)
• Abnormal kidney USG findings
• Children <2 years with non-E. coli UTI (ISPN 2024)
• Children with family history of VUR
• Boys with first UTI (some guidelines)

DMSA Scan (Technetium-99m Dimercaptosuccinic Acid)

Key MCQ: Acute phase DMSA is NOT recommended routinely. Late DMSA is only for recurrent UTI with high-grade VUR.

Summary "Top-Down" vs "Bottom-Up" Approach

• Top-down: DMSA first - identifies APN, then VCUG only if DMSA abnormal (reduces VCUG exposure)
• Bottom-up: USG + VCUG first - identifies VUR, then DMSA if needed
• ISPN recommends: RBUS first - VCUG selectively, late DMSA only if recurrent UTI + high-grade VUR

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6. Vesicoureteric Reflux (VUR) - Closely Linked to UTI

• VUR present in 25-40% of children with UTI
• Primary VUR: short intravesical ureter (congenital)
• Risk of reflux nephropathy (renal scarring) - long-term hypertension, CKD

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7. Treatment

A. Indications for Hospitalisation / IV Antibiotics

• Age <3 months (all)
• Toxic/septic appearance
• Unable to tolerate oral feeds (vomiting)
• Immunocompromised
• Obstructive uropathy
• No response to oral antibiotics after 48 hours

B. Empiric Antibiotic Choices

• Cefixime (3rd gen cephalosporin) - preferred oral agent for febrile UTI
• Amoxicillin-clavulanate
• Cefpodoxime, Cefalexin
• Co-trimoxazole (TMP-SMX) - high resistance rates in India (>50%), use cautiously
• Nitrofurantoin - lower tract only (cystitis), NOT for APN (poor renal tissue penetration)

• Ceftriaxone (drug of choice for IV)
• Ampicillin + Gentamicin (combination for sepsis in neonates)
• Piperacillin-tazobactam, Meropenem for resistant organisms

C. Duration of Treatment (ISPN 2024 / IAP STG 2022)

Key MCQ: Oral antibiotics are as effective as IV for non-toxic infants with APN (ISPN 2024, WikiGuidelines 2024).

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8. Antibiotic Prophylaxis

When IS prophylaxis indicated? (ISPN 2024)

• Children with Bladder Bowel Dysfunction (BBD)
• Children with high-grade VUR (grades 3-5)
• Children with recurrent UTIs and underlying anatomical abnormality

When is prophylaxis NOT indicated?

• Normal urinary tract after first UTI - prophylaxis NOT recommended
• Low-grade VUR (grades 1-2) in toilet-trained children without BBD
• Asymptomatic bacteriuria (do not treat)

Stopping Prophylaxis (ISPN 2024)

• Child is toilet trained
• Free of BBD
• No UTI in the last 1 year

Prophylaxis drugs

• Co-trimoxazole (TMP-SMX) 1-2 mg/kg TMP once at night
• Nitrofurantoin 1-2 mg/kg once at night (preferred in older children >3 months)
• Cephalexin (in infants <3 months, where nitrofurantoin is contraindicated)

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9. Surgical Management of VUR

• Considered for:
  • High-grade VUR (4-5) with recurrent breakthrough febrile UTIs on prophylaxis
  • Parental preference over long-term antibiotic prophylaxis
  • Failed medical management

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10. Recurrent UTI

• Full anatomical evaluation (RBUS + VCUG)
• Rule out: BBD, phimosis, vulval synechiae, constipation, renal stones
• ~50% of children with recurrent UTI have an underlying urological abnormality (IAP STG 2022)

• Timed voiding, double voiding
• High fluid intake
• Treat constipation
• Prophylaxis until BBD resolved

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11. Complications and Follow-up

• Document normal urinalysis at end of treatment
• Do NOT repeat culture unless new/breakthrough UTI
• Monitor growth, BP (every 6-12 months), renal function (yearly)

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12. Special Points for MCQs (High Yield)

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13. Recent Evidence Updates (2023-2025)

1. ISPN 2024 Guidelines (Hari P et al., Pediatr Nephrol 2024, PMID: 37897526) - Indian Society of Pediatric Nephrology evidence-based guidelines: Oral antibiotics equally effective as IV for non-toxic APN; acute DMSA not recommended; MCUG selectively in non-E. coli UTI <2 years; prophylaxis only for BBD and high-grade VUR.
2. WikiGuidelines 2024 (Nelson Z et al., JAMA Netw Open 2024, PMID: 39495518) - Multi-country consensus: most UTI topics lack high-quality prospective data; emphasises individualised approach; notes majority of recommendations are eminence-based rather than evidence-based.
3. JAMA Pediatrics Meta-analysis 2023 (Yang S et al., PMID: 37252727) - Kidney ultrasound after first febrile UTI: USG has moderate yield; most useful in detecting obstructive anomalies.

Note for INICET/NEETPG: Indian guidelines (ISPN, IAP) are increasingly being tested. Know the thresholds for MCUG, the role of DMSA, and the current position on prophylaxis. The trend is towards less aggressive imaging (no routine VCUG/acute DMSA) and oral-first antibiotic therapy for non-toxic children.