aetiology
Last reviewed 01/2018
The urethral sphincter is situated at the region of the bladder neck and proximal two-thirds of the urethra. It contributes about 50% of the total urethral resistance.
Stress urinary incontinence occurs when the proximal urethra drops below the pelvic floor because of pelvic relaxation defects. Intra-abdominal pressure is no longer transmitted equally to the bladder and proximal urethra.
This situation is most frequent:
- following childbirth - pregnancy, labour and delivery may all cause mechanical and denervation injury to the normal supports of the bladder neck and proximal urethra
- after the menopause - decreased intraurethral pressure due to oestrogen lack
Imperfect sphincter control also complicates epispadias which show a widened bladder neck, shortened urethra and separation of the symphysis pubis.