[Definition and etiologic factors of hypotonic urethra in relation to urinary stress incontinence in the female].

In 555 stress-induced urinary incontinent and 119 continent women patients, we studied the history, clinical and urodynamic investigations to define the hypotonic urethra and to find out important etiological factors of the low urethral closure pressure. The linear depression of the urethral pressure and the urethral closure pressure at rest--well known from literature--has been confirmed in this study. With hypotonic urethra, closure pressure values were found to be below the simple standard deviation from a norm-curve. Also, in cases of stress urinary incontinence, we found a nearly linear depression of closure pressure. The stress incontinent patients could be divided in two groups: 46% with hypotonic urethra, 54% with nearly normal closure pressure. History of former incontinence surgery, but also of other operations such as simple abdominal or vaginal hysterectomy, is correlated with low urethral closure pressure. The degree of closure pressure is correlated with shortening of the functional urethral length. The maximum closure pressure shifts distally. Women, who, despite hypotonic urethras, are continent, build up a positive closure pressure throughout a broad zone of the functional urethral length. Contrarily, in the case of incontinent patients, even a weak coughing spasm, which does not even break through the bladder sphincter in maximum closure, can cause opening of the urethra and establishment of pressure equilibration between bladder and urethra.