[Active forces of urinary continence and urethral fatigability. Application to stress urinary incontinence in women].

Eighteen women who had urinary stress incontinence were studied to find the existence of urethral fatigue on effort by using a sphincterometric technique. Urethral pressure measurements at rest as compared with after six heavy coughs showed a mean lowering of the urethral pressure of 40% (range 24.5%-90%) in 10 women. Spectral analysis of the electromyographic trace of the striated urethral sphincter at rest and then after coughing confirms that the striated muscle and the periurethral tissues are involved with a marked quantitative lessening of electric sphincter activity. The clinical, physiopathological, prognostic and therapeutic consequences of this new concept are discussed, together with their relationship to other active forces involved in continence.