In which part of the male urethra is a stricture most likely to occur after pelvic radiation therapy?

Radiation-Induced Urethral Strictures in Males: Location and Management

Radiation-induced urethral strictures most commonly occur in the bulbomembranous region of the male urethra following pelvic radiation therapy for prostate cancer. 1, 2

Anatomical Distribution of Post-Radiation Strictures

• Bulbomembranous urethra is the predominant location for radiation-induced strictures, with studies showing this region accounts for 82% of cases (41% bulbar, 41% membranous) 3
• The bulbomembranous location is particularly susceptible due to its proximity to the radiation field during prostate cancer treatment 2
• Less common locations include the vesicourethral junction (10%) and pan-urethral involvement (7%) 3

Radiation Modalities and Stricture Risk

• Stricture rates vary significantly based on radiation modality used 4, 1:
  • Lowest rates occur with external beam radiation therapy (EBRT) alone 1
  • Higher rates with brachytherapy 1
  • Highest rates in patients receiving combination therapy (EBRT plus brachytherapy) 1

Risk Factors for Stricture Development

• Higher radiation dose delivered to the prostatic apex 4
• Larger radiation dose per treatment fraction 4
• Prior transurethral resection of the prostate (TURP) 4
• Combined treatment modalities (external beam plus brachytherapy) 1

Diagnostic Approach

• Urethral stricture should be suspected in men with decreased urinary stream, incomplete emptying, dysuria, urinary tract infections, or rising post-void residual following radiation therapy 5, 6
• Definitive diagnosis requires one of the following 5:
  • Urethro-cystoscopy
  • Retrograde urethrography (RUG)
  • Voiding cystourethrography (VCUG)
  • Ultrasound urethrography

Management Options

• Treatment selection depends on stricture characteristics, particularly length and location 7:

  • For short bulbomembranous strictures (<2 cm): Urethral dilation or direct visual internal urethrotomy (DVIU) may be attempted initially, though success rates are limited (35-70%) 7
  • For longer strictures (≥2 cm): Urethroplasty should be offered as initial treatment due to poor success rates with endoscopic approaches 7

• Urethroplasty techniques for radiation-induced strictures 2, 3:

  • Excision with primary anastomosis is most commonly used (76-80% of cases) 2, 3
  • Buccal mucosa grafts (17%) or perineal flap repairs (7%) for more complex cases 3
  • Overall success rates of 73-90% can be achieved with appropriate technique selection 2, 3

Complications and Pitfalls

• Incontinence is a significant concern following urethroplasty for radiation-induced strictures 1, 2:

  • Transient incontinence occurs in approximately 10% of patients 2
  • Persistent incontinence affects about 40% of patients 2
  • Artificial urinary sphincter placement may be required in 13% of cases 2

• Erectile function is generally preserved following urethroplasty for radiation-induced strictures (pre-operative 47% vs. post-operative 50% erectile dysfunction rates) 2

• Repeated endoscopic treatments may cause longer strictures and increase the complexity of subsequent urethroplasty 7

• Recurrence typically occurs within the first 8 months (mean time to recurrence: 5.1 months) 2