The innervation of the DUS runs along the walls of the urethra in posterolateral fashion and has both a sympathetic and a somatic component. In patients undergoing MTF surgical approach, the DUS should not suffer any alteration, and in any case even if there was a lesion of the latter continence should be kept intact for the persistence of integrity of PUS, since male continence can be maintained even with the integrity of a single sphincter (PUS or DUS).

In this context the filling phase of the bladder should in any case be preserved even if it is believed by some that the prolonged administration of estrogen may lead to a reduction of the protective effect on the escape of urine during the increase of abdominal pressure due to a reduction of the functional length of the urethra. Of particular interest, however, is the relief of the urgency and urge incontinence in some cases. Surely, the obstructive component could be responsible for this symptomatology even if some assume that the creation of the neovagina can determine a variation of the anatomical position of the bladder with the consequent appearance of detrusor overactivity [2]. With regard to the emptying phase, it appears obvious that the shortening of the urethra is relative to the component under the sphincteric area and it is identifiable with the urethra fixed which contributes passively to empty the bladder. In any case, however, the patient changes its condition of bladder emptying both for the assumption of a no longer standing but sitting body position and finally because the reduction of urethral resistance requires a reduction of the detrusor contractility and of mechanical energy required to ensure the complete emptying of the bladder.