Fact-sheet: Posterior urethral valves


Updated on 11/03/2025 at 5:41 PM

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Definition

Congenital infravesical urinary obstruction caused by a membrane derived from the orifices of the Wolffian ducts, extending obliquely from the verumontanum to the distal prostatic urethra (type 1).
Incidence 1/4000 to 1/8000 male births. The most common cause of end-stage renal disease in children.
Detected in utero in 50% of cases during routine second-trimester ultrasound.
Poor prognostic factors are:

  • Severity of renal insufficiency at the time of diagnosis
  • Presence of high-grade vesicoureteral reflux
  • Persistence of bladder dysfunction
  • Presence of proteinuria

Radiography

Examination of choice: Retrograde voiding cystourethrography with voiding films (must include a voiding phase without catheter)

  • Typical nail-clipping (spinning top) appearance of the posterior urethra
  • Dilated, ballooned appearance of the posterior urethra
  • Assessment of bladder shape (trabeculations, diverticula) and bladder neck
  • +/- vesicoureteral reflux (50%)

Ultrasound

Suprapubic renal and bladder ultrasound

  • Bladder distension with wall thickening, along with dilation and elongation of the posterior urethra
  • Kidney morphology, pyelocaliceal dilation, and assessment of corticomedullary differentiation
  • Bilateral ureteral dilation
  • +/- peritoneal effusion due to intraperitoneal bladder rupture
  • +/- perirenal urinoma due to caliceal rupture

Perineal ultrasound of the urethra

  • Posterior urethral diameter measured via perineal approach > 6mm
  • Possible visualization of the posterior urethral valves as an echogenic band.

Management

Indication for emergency neonatal management!

  • Diagnostic confirmation: Ultrasound on day 1 of life
  • Retrograde voiding cystourethrography: assessment of bladder impact / reflux within 24h
  • Treatment: Endoscopic resection of the valves
  • if endoscopic access is not possible: percutaneous diversion for 1 month

Issues to address:

  • Immediate:
    Risk of post-obstructive diuresis syndrome: excessive urine output, electrolyte loss, and dehydration requiring correction
  • Secondary: Urinary tract infection: antibiotic prophylaxis / hydration and bladder emptying
  • Toilet training: < 3 years, neurological maturation with acquisition of bladder competence.
    Consequence of the obstruction: bladder remodeling, voiding problems: rehabilitation / self-catheterization, vesicostomy
  • Renal failure: 30% (varying degrees, evolving through adolescence)

Classification

  • Type 1: most common. Both mucosal folds extend anteriorly and inferiorly from the lower verumontanum and fuse anteriorly at the distal prostatic urethra
  • Type 2: rare and a normal variant. Mucosal folds extend along the posterolateral wall of the urethra, from the internal urethral orifice to the verumontanum
  • Type 3: "Cobb's collar". Circular diaphragm with a central opening in the membranous urethra located below the verumontanum, resulting from abnormal canalization of the urogenital membrane

Differential diagnosis

Neurogenic bladder

Prune Belly syndrome