Aetiology

Congenital:

• meatal stricture, for example, with coronal hypospadia
• bulbar stricture, for example, Cobb's collar

Acquired:

• inflammatory:
  • urethral catheterisation - common in the UK; it is influenced by:
    • duration of catheterisation - prolonged pressure on the wall of the urethra produces a zone of ischaemia that heals with a scar. The most common sites are those where the urethra is most narrow e.g. the external urethral meatus, and at points of angulation e.g. the penoscrotal junction
    • catheter material and other chemicals e.g. lubricants
    • associated infection
  • balanitis xerotica obliterans - often diagnosed late
• endarteritis obliterans - radiotherapy causing tissue damage and ischaemia
• traumatic:
  • instrumentation - especially, at the membranous urethra
  • injury to the anterior urethra from a "fall astride" - the bulbar urethra is crushed against the under surface of the pubic bone
  • injury to the posterior urethra in association with pelvic fractures; bulbar urethra may also be injured
• infective:
  • gonorrhoea - less prevalent today
  • non-specific urethritis
  • tuberculosis
• neoplastic:
  • invasion from prostatic adenocarcinoma
  • squamous carcinoma - usually in association with chronic stricture where urinary stasis has given rise to squamous metaplasia
  • transitional cell carcinoma