Urinary Tract Infections & Vesicoureteric Reflux

Forfar & Arneil 7th Edition · UTI epidemiology, risk factors, pathophysiology · Clinical presentation · Urine collection (SPA, catheter, clean catch) · Microscopy, culture · Treatment (antibiotics, prophylaxis) · Imaging (US, MCUG, DMSA) · Vesicoureteric reflux (VUR) grading, inheritance, management · Screening siblings

📌 Key principles: UTI is common in young children. Gold standard urine collection: suprapubic aspirate (SPA) or catheter. E. coli most common. Febrile UTI requires prompt antibiotics to prevent renal scarring. VUR predisposes to pyelonephritis. MCUG for VUR diagnosis. DMSA for scarring.

📖 Urinary Tract Infections & Vesicoureteric Reflux: Core Concepts

🦠 Epidemiology & risk factors
UTI occurs in 7-8% of febrile infants. More common in girls (after 1y) and uncircumcised boys (<1y). Risk factors: female sex, Caucasian race, voiding dysfunction, constipation, VUR, obstructive uropathy.
🧫 Diagnosis & urine collection
Suprapubic aspiration (SPA) – gold standard. Catheter sample (clean catch). Bag urine unacceptable (high contamination). Significant bacteriuria: ≥10⁵ CFU/ml (or any growth on SPA). E. coli >80%.
💊 Treatment
Oral antibiotics (cephalexin, co-amoxiclav, trimethoprim) for 7-10 days. IV antibiotics (ceftriaxone/gentamicin) if <3 months, toxic, vomiting, or urosepsis. Antibiotic prophylaxis (trimethoprim, nitrofurantoin) for recurrent UTI or high-grade VUR.
📷 Imaging guidelines (NICE)
<6 months: US + MCUG (if US abnormal, recurrent, or atypical). 6m-3y: US; MCUG if US abnormal or recurrent. >3y: US only if recurrent. DMSA for scarring.
🔄 Vesicoureteric reflux (VUR)
Grade I-V. Primary (immature ureteric orifice) or secondary (PUV, neurogenic bladder). Family screening (siblings) – 27-50% risk. Prophylaxis for high grade (III-V). Surgery if breakthrough infections.

📊 Key facts: Febrile UTI risk of renal scarring 10-20% (higher with delayed treatment, high-grade VUR). DMSA scan 4-6 months after infection to detect scarring.

🔍 Clinical approach to UTI and VUR in children

Suspect UTI in febrile child without source – Especially <2 years. Ask about poor feeding, vomiting, lethargy, malodorous urine. Older children: dysuria, frequency, abdominal pain.

Collect urine before antibiotics – SPA or catheter for infants; clean catch for older cooperative children. Bag urine NOT for culture (high false positives).

Interpret urine dipstick – Nitrite + leukocyte esterase (high sensitivity/specificity). Positive dipstick → treat pending culture. Negative dipstick makes UTI unlikely but not excluded.

Start appropriate antibiotics – Oral cephalexin/co-amoxiclav for well child. IV ceftriaxone/gentamicin if <3 months, septic, vomiting. Duration 7-10 days.

Arrange imaging based on age and severity – <6 months: ultrasound + MCUG (if abnormal or recurrent). DMSA for scarring if recurrent or high risk.

VUR diagnosis and grading – MCUG grades I-V. Prophylaxis for high-grade (III-V). Surgical reimplantation or endoscopic injection for breakthrough infections.

📌 Clinical pearl: In a febrile infant <3 months, UTI is a serious bacterial infection. Requires hospital admission, IV antibiotics, and full septic workup. Delayed treatment increases risk of renal scarring.

📋 Stepwise management of UTI and VUR

Acute UTI – antibiotics – Oral (cephalexin 50 mg/kg/day, co-amoxiclav, trimethoprim) for 7-10 days. IV (ceftriaxone 50 mg/kg/day or gentamicin) for severe illness. Paracetamol for fever/pain.

Antibiotic prophylaxis indications – Recurrent UTIs (≥2 pyelonephritis or 3 cystitis/year), high-grade VUR (III-V), or after pyeloplasty. Trimethoprim or nitrofurantoin (single nightly dose).

Imaging after first febrile UTI (UK NICE) – <6m: ultrasound during acute infection, MCUG if US abnormal or recurrent. 6m-3y: ultrasound within 6 weeks. MCUG only if US abnormal, recurrent, or atypical. >3y: US only if recurrent.

VUR – medical management – Prophylaxis for grade III-V. Monitor for breakthrough UTIs. Annual US, DMSA if scarring suspected. Constipation treatment, voiding dysfunction management.

VUR – surgical management – Endoscopic injection (Deflux) or ureteric reimplantation. Indications: breakthrough UTIs on prophylaxis, high grade V (IV-V) with scarring, poor compliance, parental choice.

Screening siblings of VUR – MCUG in siblings of index case (27-50% risk). Screen infants early.

⚠️ VUR grading (International Reflux Study): Grade I: ureter only; II: pelvis, no calyceal dilatation; III: mild/moderate dilatation; IV: moderate dilatation, blunted calyces; V: severe dilatation, tortuous ureter.

🧠 Reflex prompts: UTI & VUR

🦠 A 2-month-old with fever 39°C, no source. Urine dipstick: nitrite positive, leukocyte esterase positive. Next step?
Collect urine by SPA or catheter before antibiotics. Start IV ceftriaxone or gentamicin. Full septic workup.
🧪 What is the most common organism causing UTI in children?
Escherichia coli (80-90%). Others: Klebsiella, Proteus, Enterococcus, Pseudomonas.
📷 A 4-month-old with first febrile UTI, ultrasound normal. What imaging is recommended (NICE UK)?
Ultrasound during acute infection is sufficient. MCUG only if US abnormal, recurrent, or atypical (e.g., non-E. coli, poor response).
🔄 A 3-year-old girl with recurrent febrile UTIs, MCUG shows grade IV VUR. Management?
Antibiotic prophylaxis (trimethoprim). Consider surgical reimplantation if breakthrough infections or new scarring.
👶 A 1-year-old with febrile UTI, DMSA scan shows renal scarring. Long-term follow-up?
Monitor blood pressure annually. Check proteinuria, eGFR. ACE inhibitor if hypertension or proteinuria.
🧬 A child has VUR grade III. What is the risk for siblings?
27-50% risk. Screen siblings with MCUG (especially if <2 years and febrile UTI risk).
💊 What is the first-line antibiotic for UTI prophylaxis?
Trimethoprim or nitrofurantoin (single nightly dose). Avoid in infants <3 months (nitrofurantoin).
🩸 A 6-year-old with recurrent UTIs, normal ultrasound, no VUR on MCUG. Next step?
Assess for voiding dysfunction, constipation, poor hygiene. Treat constipation (polyethylene glycol). Urotherapy.
🔬 What is the gold standard urine collection method for an infant?
Suprapubic aspiration (SPA). Catheter sample is acceptable alternative. Bag urine is NOT suitable for culture.
📈 When should DMSA scan be performed to assess for renal scarring?
4-6 months after acute febrile UTI (to allow resolution of reversible defects).