Well its a pretty hot topic among uro's and they're trying to get it right which is why they probably keep telling women to get them even though success rate is around 33% as compared to 90% with men.
www.urotoday.com/3391/urotoday_international_journal/female_urology/hypercontinence_in_women_after_
Introduction: There is a great debate about the cause of the higher incidence of hypercontinence in women undergoing orthotopic diversion after cystectomy in relation to men.
Conclusion: The relaxation of the striated sphincter and the contraction of the longitudinal smooth muscle opens the way for micturition. The loss of this normal coordinated reflex leads to the presence of a urethra with a fixed tone that does not open with trials of evacuation. As men and women have an intact striated sphincter, the higher incidence of hypercontinence in females compared to males is due to the presence of the extra tone of the urethral smooth muscles. This study proves that the more urethral length left, the higher the incidence of hypercontinence because more smooth muscle tone is faced during micturition. Nerve preservation has no impact because the coordinated detrusor urethral smooth muscle action is lost.
Pat