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Q1: The febrile infant (2 min)
"A febrile, irritable, vomiting 4-month-old has no focus of infection. What do you do, and why?"
- UTI must be excluded — infants present NON-SPECIFICALLY (fever without source, poor feeding, vomiting, irritability, prolonged jaundice in neonates).
- Obtain a PROPERLY COLLECTED urine for culture: SPA (gold standard in infants) or catheter. A bag urine is not diagnostic.
- Culture thresholds: SPA any growth; catheter 10^4 to 10^5; clean-catch over 10^5 (over 10^4 with pyuria).
- Do NOT call it "just a virus" without sampling urine — the trap that causes missed pyelonephritis and renal scarring.
Q2: Organisms and risk factors (2 min)
"What organisms cause childhood UTI and which children are at risk?"
- E. coli in 75 to 85 percent; Klebsiella, Proteus (struvite stones), Enterococcus, Pseudomonas (instrumented/recurrent), Staph saprophyticus (adolescent girls).
- Risk factors: female sex (short urethra), uncircumcised boys, constipation, voiding dysfunction, VUR, posterior urethral valves (boys), neurogenic bladder, structural anomaly.
- Mechanism: ASCENDING infection — P-fimbriated E. coli adhere to uroplakin receptors; VUR delivers infected urine to the kidney.
Q3: Treatment (3 min)
"How do you treat a lower UTI versus pyelonephritis in a child?"
- LOWER UTI (cystitis): well child over 3 months — 3 days oral (trimethoprim, nitrofurantoin, cefalexin, co-amoxiclav per local resistance).
- UPPER UTI / pyelonephritis: 7 to 10 (up to 14) days. Oral co-amoxiclav/cefixime if well; IV ceftriaxone/co-amoxiclav/gentamicin if young (under 3 months), unwell, dehydrated, vomiting, septic or non-responsive — switch oral when afebrile.
- Avoid nitrofurantoin for upper UTI (poor renal tissue penetration).
- Neonate (<1 month): treat as neonatal sepsis (ampicillin + gentamicin or cefotaxime), full workup including LP.
Q4: Investigation pathway (2 min)
"When do you image after a UTI, and with what?"
- Ultrasound: all under 6 months; any age if atypical or recurrent.
- DMSA scintigraphy 4 to 6 months after an upper/recurrent UTI — detects permanent renal scarring.
- MCUG selectively: atypical/recurrent, boys under 6 months (exclude posterior urethral valves), suspected high-grade VUR.
- Atypical UTI = seriously ill, poor urine flow, abdominal/bladder mass, raised creatinine, non-E. coli, or no response at 48 hours. Recurrent = 2+ upper, 3+ lower, or 1 upper + 1 lower.
Q5: VUR, scarring and prevention (2 min)
"What is VUR, why does it matter, and how do you prevent recurrence?"
- VUR = incompetent ureterovesical junction allowing reflux of infected bladder urine to the kidney; graded I to V.
- Consequence: pyelonephritis + scarring -> hypertension and CKD.
- Low-grade (I-II): conservative, usually resolves spontaneously. High-grade (IV-V) with recurrent pyelonephritis/scarring: surgery (endoscopic STING bulking or ureteric reimplantation).
- Prevention: treat CONSTIPATION and bladder-bowel dysfunction (most effective reversible driver), ensure hydration and double-voiding; prophylaxis (trimethoprim 2 mg/kg nocte) for recurrent UTI/high-grade VUR; circumcision selectively for boys with recurrent UTI + high-grade VUR.