Urethral and perineal instability.

50 out of 271 female patients showed urethral pressure variations of at least 15 cm H2O during bladder filling. These pressure fluctuations were accompanied by variations in the EMG activity of the anal and periurethral striated musculature. Urethral instability is frequently associated with bladder overactivity and occurs in younger people. Possible pathophysiological mechanisms and implications for therapy are discussed.