What imaging is recommended for a 5-year-old boy with urinary retention?

Imaging for Urinary Retention in a 5-Year-Old Boy

Ultrasonography (US) of the kidneys and bladder should be the initial imaging study for a 5-year-old boy with urinary retention. 1

Initial Imaging Approach

First-Line Imaging

• Renal and bladder ultrasonography:
  • Provides non-invasive assessment without radiation exposure
  • Can detect anatomical abnormalities such as:
    • Hydronephrosis
    • Duplex renal systems
    • Ureterocele
    • Bladder wall thickening
    • Bladder distension
    • Post-void residual urine volume
    • Fecal impaction (a common cause of urinary retention in children)
  • Should include pre-void and post-void bladder assessment to evaluate for retention syndrome 1

When to Consider Additional Imaging

After initial ultrasonography, additional imaging should be guided by findings and clinical presentation:

1. If US shows anatomical abnormalities:

   • Voiding cystourethrography (VCUG) should be considered, especially in boys where posterior urethral valves are a concern 1
   • VCUG is particularly important for evaluating suspected urethral causes such as:
     • Posterior urethral valves
     • Urethral polyps
     • Meatal stenosis
     • Urethral stricture 1

2. If neurological causes are suspected:

   • Consider spinal MRI to evaluate for:
     • Tethered cord
     • Spinal dysraphism
     • Spinal cord tumors 2

Common Causes of Urinary Retention in Children

Understanding the etiology helps guide appropriate imaging:

• Neurological processes (17% of cases) 2
• Severe voiding dysfunction (15%) 2
• Urinary tract infection (13%) 2
• Constipation (13%) 2
• Adverse drug effects (13%) 2
• Local inflammatory causes (7%) 2
• Locally invading neoplasms (6%) 2
• Benign obstructing lesions (6%) 2

Important Considerations

• Urinary retention in children is relatively rare but has significant association with neurological abnormalities 2
• Boys are more likely to have obstructive causes (posterior urethral valves, benign prostatic hyperplasia) 2
• In-office ultrasonography has demonstrated 98% sensitivity and 82% specificity for detecting urological abnormalities in children 3
• Avoid unnecessary radiation exposure by starting with ultrasonography before considering other imaging modalities 4

Pitfalls to Avoid

• Don't start with CT scanning as the initial imaging study due to radiation exposure concerns in children
• Don't skip bladder assessment during ultrasonography - both pre-void and post-void images are essential
• Don't assume constipation isn't the cause - fecal impaction is a common and treatable cause of urinary retention in children that can be visualized on ultrasound
• Don't miss neurological red flags - if no clear anatomical cause is found on initial imaging and history suggests neurological involvement, prompt neurological evaluation and appropriate spinal imaging should be pursued 2

Ultrasonography provides the best balance of diagnostic utility and safety for the initial evaluation of urinary retention in a 5-year-old boy, with additional imaging guided by these initial findings.