In a pediatric patient with recurrent urinary tract infections presenting with dysuria and a urinalysis positive for nitrites and leukocytes, which investigation is most indicated?

Renal Ultrasound is the Most Indicated Investigation

For a pediatric patient with recurrent UTI presenting with dysuria and positive nitrites/leukocytes, renal and bladder ultrasound (RBUS) is the most indicated investigation. The correct answer is B - Renal US.

Rationale Based on Current Guidelines

Why Renal Ultrasound Alone

• The American Academy of Pediatrics (AAP) recommends RBUS for all children with recurrent febrile UTIs to detect anatomic abnormalities such as hydronephrosis, scarring, or structural defects that require further evaluation. 1

• RBUS is the first-line imaging modality with a 9/9 appropriateness rating from the American College of Radiology (ACR), providing excellent detection of structural abnormalities without radiation exposure. 1

• The prevalence of vesicoureteral reflux (VUR) increases from 35% to 74% in children with recurrent UTIs, and each infection episode increases the risk of renal scarring. 2

Why NOT Voiding Cystourethrography (VCUG) Immediately

• VCUG is specifically indicated AFTER the second febrile UTI, not routinely after the first or for recurrent infections without first obtaining ultrasound results. 1, 3

• The AAP explicitly states that VCUG should be performed if RBUS reveals hydronephrosis, scarring, or findings suggesting high-grade VUR or obstructive uropathy—meaning ultrasound guides the decision for VCUG. 1

• VCUG involves urethral catheterization and radiation exposure (RRL = ☢☢), making it more invasive than ultrasound and inappropriate as a first-line test. 1

Clinical Algorithm for Recurrent UTI Imaging

Step 1: Obtain renal and bladder ultrasound first 1, 2

Step 2: If ultrasound shows:

• Normal findings: Monitor clinically, instruct parents to seek prompt evaluation for future fevers 1, 3
• Hydronephrosis, scarring, or structural abnormalities: Proceed to VCUG 1
• After a second febrile UTI: Proceed to VCUG regardless of ultrasound findings 1, 3

Why the Other Options Are Incorrect

• Option A (VCUG alone): Skips the essential first-line ultrasound evaluation and exposes the child to unnecessary radiation and catheterization without first ruling out structural abnormalities that ultrasound can detect. 1

• Option C (Both VCUG and Renal US): Ordering both simultaneously is not evidence-based; ultrasound findings should guide whether VCUG is needed, avoiding unnecessary invasive procedures. 1

• Option D (KUB US): A plain abdominal radiograph (KUB) has very limited utility in UTI evaluation and is rated as "usually not appropriate" by the ACR for this indication. 1

Critical Management Points

• Approximately 15% of children develop renal scarring after their first UTI, which can lead to hypertension (5%) and chronic kidney disease (3.5% of pediatric ESRD cases). 3, 2

• Early treatment within 48 hours of fever onset reduces renal scarring risk by more than 50%. 3

• Parents should be instructed to seek prompt medical evaluation (ideally within 48 hours) for any future febrile illness to detect recurrent infections early. 1, 3

Common Pitfall to Avoid

Do not order VCUG as the initial imaging study for recurrent UTI. The evidence-based approach requires ultrasound first to stratify risk and guide further invasive testing, minimizing radiation exposure and patient discomfort while still identifying all clinically significant abnormalities. 1