When should a renal and bladder ultrasound be performed in a child with recurrent urinary tract infections?

Renal and Bladder Ultrasound for Recurrent UTIs in Children

Perform renal and bladder ultrasound (RBUS) after the first episode of recurrent UTI in children of any age to detect underlying anatomical abnormalities, calculi, or complications such as renal or perirenal abscess. 1

Age-Specific Imaging Algorithms

Infants Under 2 Months

• RBUS is mandatory for all UTIs in this age group due to high risk of underlying urologic abnormalities (hydronephrosis found in 45% of cases) and bacteremia (4-36.4% of cases) 1, 2
• Perform imaging during acute infection if atypical presentation, or within 6 weeks if typical infection 1

Children 2 Months to 6 Years

• RBUS is the primary imaging study recommended after first febrile UTI 1, 3
• For recurrent UTI (defined as ≥2 episodes of pyelonephritis, OR 1 pyelonephritis plus ≥1 cystitis, OR ≥3 episodes of cystitis), RBUS is usually appropriate to detect underlying abnormalities 1, 2
• The American Academy of Pediatrics recommends RBUS for children 2-24 months with febrile UTI 1

Children Over 6 Years

• RBUS is not routinely indicated for uncomplicated first febrile UTI in this age group, as the yield is extremely low 2, 3
• However, RBUS should be performed for recurrent or atypical UTI at any age 1, 2

Definition of Recurrent UTI

The American College of Radiology defines recurrent UTI as: 2

• 2 or more episodes of UTI with acute pyelonephritis/upper tract UTI, OR
• 1 episode of pyelonephritis plus 1 or more episodes of cystitis/lower tract UTI, OR
• 3 or more episodes of cystitis/lower tract UTI

Additional Imaging Considerations for Recurrent UTI

Voiding Cystourethrography (VCUG) or Voiding Urosonography (VUS)

• VCUG or VUS is usually appropriate for recurrent UTI given the increased prevalence of vesicoureteral reflux (VUR increases from 35% to 74% in children with recurrent UTI) 1
• The American Academy of Pediatrics suggests VCUG for children 2-24 months after the second febrile UTI 1
• NICE guidelines recommend VCUG for children 6 months to 3 years with atypical UTI and abnormalities on RBUS, poor urine flow, or family history of VUR 1
• VCUG is not recommended by NICE for children >3 years even with recurrent UTI 1

DMSA Renal Scan

• Recommended 4-6 months after atypical or recurrent infection in children <3 years 1
• For children >3 years, DMSA is recommended for recurrent infection 1
• A normal DMSA scan may exclude high-grade reflux and direct toward antibiotic treatment without invasive VCUG 1

CT Abdomen/Pelvis with IV Contrast

• Reserved only for suspected complications such as renal abscess or xanthogranulomatous pyelonephritis 1, 2
• Not indicated for routine evaluation of recurrent UTI 1

Key Clinical Pitfalls to Avoid

• Do not skip RBUS in recurrent UTI regardless of age, as it detects underlying abnormalities in a significant proportion of cases (38% abnormal in one study) 4
• Do not use RBUS as a screening test for VUR due to poor sensitivity (detects only ~25% of VUR cases) 1, 2
• Do not routinely order CT imaging for recurrent UTI; reserve for suspected complications only 1, 2
• Be aware that normal RBUS does not exclude VUR: 24% of children with normal RBUS had dilating VUR in one study, and 15% had recurrent pyelonephritis 4
• Counsel parents that even with normal RBUS, the child may still have VUR, recurrent pyelonephritis, and potential need for surgical intervention 4

Atypical UTI Features Requiring Imaging

Perform RBUS during acute infection if any of the following are present: 2

• Seriously ill appearance
• Poor urine flow
• Abdominal or bladder mass
• Elevated creatinine
• Septicemia
• Failure to respond to appropriate antibiotics within 48 hours
• Infection with non-E. coli organisms