Urinary Tract Infection

Introduction And Epidemiology

• Urinary tract infection (UTI) is a very common bacterial infection during childhood.
• It affects approximately 1.7% of boys and 8.4% of girls before they reach the age of seven years.
• Delaying the diagnosis and treatment can cause irreversible damage to the developing kidneys.
• Long-term complications include renal scarring, hypertension, and renal insufficiency.

Etiology And Risk Factors

• Escherichia coli (E. coli) is the most common causative organism, accounting for >70% of cases.
• Uncommon organisms include non-E. coli bacteria and fungi.
• Fungal UTIs are typically seen in immunocompromised patients, intensive care unit settings, prolonged antibiotic usage, and with indwelling catheters.
• Almost 50% of children with recurrent UTI and 10% presenting with a single UTI have an associated urological abnormality.

Common Risk Factors

• Poor perineal hygiene and the unnecessary use of diapers.
• Congenital anomalies of the kidney and urinary tract (CAKUT), including vesicoureteral reflux (VUR), pelvic ureteric junction obstruction, and obstructive uropathy.
• Anatomic variations like phimosis in boys and vulval synechiae in girls.
• Bladder-bowel dysfunction (BBD) presenting as urinary urgency, frequency, voiding postponement, incontinence, and constipation.

Clinical Presentation And Definitions

Symptomatology By Age

• Infants often present with non-specific symptoms such as fever, vomiting, diarrhea, and poor weight gain.
• Older children typically present with fever, dysuria, urgency, frequency, and abdominal or flank pain.

Standard Definitions

Diagnostic Approach

Sample Collection Strategies

• Urine samples should be processed within 30 minutes of collection to avoid contamination.
• Samples must never be collected using a urobag or minicom.

Laboratory Investigations

• Screening Test: A positive urine dipstick for leukocyte esterase and nitrite combination is suggested as a first-line screening tool for presumptive UTI.
• Microscopy: Urine microscopy for bacteriuria and leukocyturia in a freshly voided sample is an acceptable alternative to the dipstick.
• Gold Standard: Diagnosis is confirmed by isolating a single species of microorganism in a significant number from a properly collected culture.

Significant Colony Counts For Diagnosis

• The Indian Society of Pediatric Nephrology (ISPN) has lowered the threshold for positive cultures to prevent missing true UTIs.

Asymptomatic Bacteriuria

• Defined as significant bacteriuria without pyuria or clinical symptoms.
• It is often associated with nonvirulent E. coli colonization and is more common in girls.
• It should not be treated with antibiotics, and urine cultures are not indicated in asymptomatic children.

Management Strategies

Principles Of Antimicrobial Therapy

• Antibiotic therapy must be initiated promptly, preferably within 48 to 72 hours of fever onset to minimize kidney damage.
• The oral route is preferred over intravenous therapy for acute febrile UTI.
• Intravenous antibiotics are reserved for infants less than 2 months of age, severely ill patients, and those unable to tolerate oral intake.
• Change of initial therapy is only suggested for clinical treatment failure, regardless of in vitro sensitivity patterns.
• Routine repeat urine cultures are not required if the patient shows good clinical response.

Treatment Duration And Regimens

Approach Based On Severity

Uncomplicated First UTI

• Seen in children >3 months who are nontoxic and accepting oral feeds.
• Start oral antibiotics and evaluate clinical and pyuria improvement by 48 hours.

Complicated Or Atypical UTI

• Risk features include age <3 months, fever >39 C, lethargy, dehydration, renal angle tenderness, elevated creatinine, or non-E. coli infections.
• Requires hospitalization, intravenous fluids, and empirical intravenous antibiotics.
• Switch to oral antimicrobials after 48 hours once symptomatic improvement is achieved.

Common Antimicrobial Dosages

Imaging Guidelines

• The updated ISPN guidelines advise a less aggressive approach to imaging, aiming primarily to detect high-grade VUR.

graph TD
    A[Confirmed UTI Episode] --> B[Assess for BBD and Perform Ultrasound Scan]
    B --> C{Are there specific risk factors present?}
    C -- Yes: Abnormal Ultrasound OR Recurrent UTI OR Non-E.coli in child <2 years --> D[Perform Micturating Cystourethrography]
    C -- No: Normal Ultrasound and isolated E.coli UTI --> E[Watch for recurrence and monitor]
    D --> F{Is High-Grade VUR Present OR does UTI recur?}
    F -- Yes --> G[Perform Late-Phase DMSA Scan at 4 to 6 months]
    F -- No --> E

Prevention And Prophylaxis

Antimicrobial Prophylaxis

• Routine antibiotic prophylaxis is not suggested for patients with a normal urinary tract and no bladder-bowel dysfunction.
• It is also not suggested for children with antenatally detected hydronephrosis awaiting evaluation.
• Indications: High-grade VUR (Grades 3-5), recurrent febrile UTI with BBD, and pending radiological evaluation after a first episode.
• Preferred Agents: Cotrimoxazole (1-2 mg/kg of trimethoprim) or nitrofurantoin (1-2 mg/kg) in children older than 3 months. Cephalexin is preferred for young infants under 3 months.
• Discontinuation Criteria: Prophylaxis can be stopped in children >2 years if they are toilet trained, have no BBD, and have had no febrile UTIs in the preceding year.

Non-Antibiotic Interventions

• Urotherapy: Recommended for all children with BBD to prevent recurrence. It includes behavioral modifications, fluid intake optimization, and regular voiding habits.
• Cranberry Products: Can be considered for preventing recurrent UTI in children with a normal urinary tract.
• Circumcision: Considered a potential intervention to reduce the risk of recurrence in at-risk children.
• Surgical Reimplantation: Reserved for patients with high-grade VUR experiencing recurrent breakthrough febrile UTIs despite antibiotic prophylaxis.

Follow-Up And Monitoring

• Ensure symptomatic improvement and documented normal urine analysis at the end of treatment.
• Monitor growth periodically.
• Blood pressure should be evaluated every 6 to 12 months.
• Assess renal function annually in children with a history of severe complicated UTI or recurrent episodes.
• Monitor for proteinuria after successful treatment, as it may indicate pyelonephritic renal scarring requiring medical intervention.

Algorithm for MRCPCH based on NICE guidelines

graph TD
    A[Child with Confirmed UTI] --> B{Age Group}
    
    %% Under 6 Months
    B -->|Under 6 Months| C{Clinical Presentation}
    C -->|Responds well within 48h| D[Ultrasound within 6 weeks. 
 If abnormal, consider MCUG.]
    C -->|Atypical UTI| E[Ultrasound during acute infection. 
 DMSA scan 4 to 6 months after. 
 MCUG recommended.]
    C -->|Recurrent UTI| F[Ultrasound during acute infection. 
 DMSA scan 4 to 6 months after. 
 MCUG recommended.]
    
    %% 6 Months to under 3 Years
    B -->|6 Months to under 3 Years| G{Clinical Presentation}
    G -->|Responds well within 48h| H[No routine imaging. 
 Note: If non-E. coli, Ultrasound within 6 weeks.]
    G -->|Atypical UTI| I[Ultrasound during acute infection. 
 DMSA scan 4 to 6 months after. 
 Consider MCUG if specific features present.]
    G -->|Recurrent UTI| J[Ultrasound within 6 weeks. 
 DMSA scan 4 to 6 months after.]
    
    %% 3 Years or Older
    B -->|3 Years or Older| K{Clinical Presentation}
    K -->|Responds well within 48h| L[No routine imaging. 
 Note: If non-E. coli, Ultrasound within 6 weeks.]
    K -->|Atypical UTI| M[Ultrasound during acute infection.]
    K -->|Recurrent UTI| N[Ultrasound within 6 weeks. 
 DMSA scan 4 to 6 months after.]