✅ Model Answer:
• Diagnosis: Cystitis (lower urinary tract infection) — dysuria, frequency, urgency, suprapubic pain, no fever. UA shows leukocyte esterase +, nitrite +, 50 WBC/hpf. Urine culture grew E. coli >100,000 CFU/mL. Normal renal function and normal renal ultrasound rule out pyelonephritis and obstruction.
• Any other test: Urine culture with susceptibility (already done). Consider renal/bladder ultrasound if recurrent UTI, atypical features, or in boys (already done — normal).
• What to do next: Start oral antibiotics — cephalexin 50-100 mg/kg/day divided q6h, or TMP-SMX (if susceptible), or nitrofurantoin (for cystitis only). Ensure adequate hydration. Treat for 3-5 days.
• Follow-up plan: No routine post-treatment culture. Counsel on prevention: adequate hydration, voiding regularly, wiping front-to-back, treating constipation. If recurrence, evaluate for VUR or dysfunctional voiding.

✅ Model Answer:
• Cystitis is an infection of the bladder (lower urinary tract infection), typically caused by bacteria entering the urethra and ascending to the bladder.
• Common organisms:
- Escherichia coli: Most common (80-90% of UTIs).
- Klebsiella pneumoniae
- Proteus mirabilis (associated with stones)
- Enterococcus faecalis
- Staphylococcus saprophyticus (more common in adolescents)
- Group B Streptococcus (in neonates)
• Risk factors:
- Female gender (shorter urethra)
- Poor hygiene (wiping back-to-front)
- Constipation
- Infrequent voiding
- Sexual activity (adolescents)
- Anatomic abnormalities (VUR, obstruction)
- Immunosuppression
• Age: Can occur at any age; more common in girls after toilet training.

✅ Model Answer:
• Cystitis (lower UTI):
- Symptoms: Dysuria, frequency, urgency, suprapubic pain, cloudy or foul-smelling urine.
- Fever: Usually absent.
- Systemic symptoms: None.
- Urinalysis: Pyuria, nitrites, positive leukocyte esterase.
- WBC casts: Absent.
- Renal function: Normal.
- Treatment: Oral antibiotics 3-5 days.
• Pyelonephritis (upper UTI):
- Symptoms: Fever, chills, flank pain, vomiting, ill-appearing.
- Fever: Usually present (≥38.5°C).
- Systemic symptoms: Malaise, anorexia, dehydration.
- Urinalysis: Pyuria, nitrites, WBC casts, proteinuria.
- WBC casts: Present (indicates renal involvement).
- Renal function: May be elevated (if AKI).
- Treatment: IV antibiotics (initially), then oral, total 7-10 days.

✅ Model Answer:
• Urinalysis findings:
- Leukocyte esterase: Positive (indicates WBCs in urine).
- Nitrites: Positive (indicates bacteria that reduce nitrates to nitrites — E. coli, Klebsiella, Proteus).
- WBC (pyuria): >5-10 WBC/hpf (elevated).
- RBC: May be present (hematuria).
- Protein: Mild proteinuria (trace to 1+).
- Bacteria: Present on microscopic exam.
- Casts: None (if WBC casts are present, suspect pyelonephritis).
- pH: May be alkaline (if Proteus).
- Specific gravity: Variable.
• Gold standard: Urine culture (>100,000 CFU/mL of a single organism).

✅ Model Answer:
• Antibiotic therapy:
- First-line (oral):
• Cephalexin: 50-100 mg/kg/day divided q6h (safe, effective).
• Nitrofurantoin: 5-7 mg/kg/day divided q6h (for cystitis only — NOT for pyelonephritis).
• TMP-SMX: 6-10 mg TMP/kg/day divided q12h (if susceptible and age >2 months).
• Amoxicillin-clavulanate: 30-50 mg/kg/day (based on amoxicillin component).
- Duration: 3-5 days for uncomplicated cystitis.
• Supportive care:
- Adequate hydration.
- Avoid irritants (caffeine, spicy foods).
- Phenazopyridine (urinary analgesic) — for symptomatic relief (not for children <6 years).
• If no improvement in 48-72 hours: Re-evaluate for resistant organism or pyelonephritis.

✅ Model Answer:
• Nitrofurantoin: An oral antibiotic used specifically for cystitis (lower UTI).
• Mechanism: Inhibits bacterial enzymes (broad spectrum, including E. coli).
• Indications: Uncomplicated cystitis in children >1 month of age.
• Dose: 5-7 mg/kg/day divided q6h (max 400 mg/day).
• Duration: 5-7 days (or 3-5 days for uncomplicated cystitis).
• Advantages: Low resistance rates, good GI absorption, minimal systemic side effects.
• Contraindications: NOT for pyelonephritis (does not achieve adequate tissue concentrations).
• Not for: Renal impairment (CrCl <60 mL/min), neonates <1 month, G6PD deficiency.
• Side effects: GI upset, urine discoloration (brown/yellow).

✅ Model Answer:
• Complications:
- Pyelonephritis: Ascending infection to the kidneys → fever, flank pain, systemic illness.
- Renal abscess: Collection of pus in the kidney (if pyelonephritis is untreated).
- Urosepsis: Bacteremia from UTI (can be life-threatening).
- Vesicoureteral reflux (VUR): May be unmasked or worsened by recurrent UTIs.
- Renal scarring: Chronic pyelonephritis → hypertension, CKD.
- Recurrent UTIs: Increased risk of recurrence if underlying causes are not addressed (constipation, voiding dysfunction).
- Growth failure: In infants with recurrent UTIs.
- Death: Rare, but possible if urosepsis occurs.

✅ Model Answer:
• Prognosis:
- Excellent: With appropriate antibiotic therapy, symptoms resolve within 48-72 hours.
- Complete recovery: Most children recover without complications.
- Recurrence: 10-30% of children may have recurrent UTIs (especially if risk factors are present).
- No long-term sequelae: If treated promptly and adequately.
- Mortality: Extremely low.
• Long-term follow-up:
- No routine follow-up: For uncomplicated cystitis.
- If recurrence: Evaluate for VUR, dysfunctional voiding, constipation.
- Education: Counsel on prevention: adequate hydration, voiding regularly, wiping front-to-back, treating constipation.
- Consider: Renal/bladder ultrasound if recurrent or atypical features.