The unstable urethra in the female.

The clinical and urodynamic characteristics of 54 women with unstable urethras (falls of urethral pressures of at least 20 cm H2O) were compared with those of 171 patients with stable urethras. The unstable-urethra patients were younger and presented with an increased incidence of marked urgency and a lower incidence of genuine stress incontinence. The average urethral pressure fall was preceded by a 6-cm increase in maximum urethral pressure. The mean (+/- SD) fall of urethral pressure was 30 +/- 12 cm H2O and the average duration of the event was 8 seconds. The level of the urethral pressure fall was not influenced by bladder volume but correlated positively with higher maximum urethral pressures. The present findings suggest that the unstable urethra plays a limited role in genuine stress incontinence but may be linked with the unstable detrusor.