Stress urinary incontinence

Stress urinary incontinence due to urethral sphincter incompetence (genuine stress incontinence) afflicts some 5-15% of women. The mechanism of continence is imperfectly understood, as is the precise mode of its cure, whether conservative or surgical. The pathophysiology is a reduction in urethral resistance in the absence of detrusor activity. Aetiological factors include congenital malformation of the bladder neck, denervation of the pelvic floor and sphincter mechanism following childbirth, trauma causing disruption of the urethral sphincter mechanism, fibrosis associated with bladder neck surgery for prolapse, oestrogen deprivation at the menopause, and urethral relaxation or instability. Conventional investigations include urethral pressure measurement, urethral electric conductance, electrophysiological tests, and cystometry or videocystourethrography (the latter procedures diagnose by exclusion). A more precise evaluation of the role of urethral resistance is hampered by lack of suitable techniques for measuring urethral and sphincteric function. Treatments include pelvic floor exercise, drugs to increase urethral resistance, and surgery, either to evaluate the bladder neck or to increase urethral resistance.