Urinary incontinence: anatomy, physiology and pathophysiology

Urinary continence in the female depends on urine being stored in a receptive bladder closed by a competent sphincter mechanism. Incontinence can result from a failure of storage, i.e. detrusor instability or a failure of the sphincter mechanism leading to stress incontinence. In addition there is a complex neural control which co-ordinates urethral and bladder function to alter from storage to voiding at socially acceptable times. Although the majority achieve continence early in childhood, there are a number of insults brought to bear on the continence mechanism other than advancing age. The most notable of these is childbirth with resultant neuromuscular damage to the pelvic floor. The onset of the menopause with oestrogen deprivation and increased risk of urinary tract infection can further compromise bladder function. Restoration of continence in those affected involves a thorough knowledge of normal functioning anatomy and physiology of the lower urinary tract as only through improved understanding of disease mechanisms can rational treatment be applied.