Editing Functional: Urinary Incontinence (section)

== Pathophysiology of SUI in Females ==

* Original theories explaining the pathophysiology of urinary incontinence in females focused on the descent of the proximal urethra and bladder neck. It was believed that as the urethra became hypermobile, intraperitoneal forces could no longer constrict the urethra and incontinence resulted.
* '''Posterior musculofascial fascial/ligamentous support of the urethra from the anterior vaginal wall and extending laterally from the vagina to the levator ani and arcus tendineus fascia pelvis contribute to the maintenance of continence seen at times of increases in intraabdominal pressure'''.
** It is compression of the urethra against this firm posterior backing (hammock) that enables the urethra to prevent urinary loss with stress maneuvers. 
**'''Loss of backing from this musculofascial support leads to incontinence because of an inability to compress the urethra.'''
*** '''This theory suggests that repositioning the urethra, previously considered to be essential, is not necessarily essential to restoring continence in females who leak with SUI.''' 
***'''The essential element to restoring continence rests with restoring the layer of support to the posterior urethra and therefore allowing the urethra to be compressed adequately.'''
* '''Intrinsic Sphincteric Deficiency'''
** '''Some women with no hypermobility have fairly severe SUI which is the concept of intrinsic sphincteric deficiency'''
** '''Patients with ISD have classically been described as having a “pipe stem” urethra, meaning a fixed urethra with little intrinsic closure function. This finding may result from previous surgery and is typically iatrogenic in some way.'''
** '''Subtler forms of ISD, which typically coexist with the finding of urethral hypermobility, are more commonly found and are likely responsible for most forms of SUI.''' 
***ISD in this setting may be secondary to ischemic injury (birth or other trauma) or other forms of progressive pudendal nerve damage.
** ISD was historically identified urodynamically using the concept of abdominal leak point pressure (ALPP).
*** ALPP testing describes the abdominal pressure required to cause urethral incontinence.
*** '''Low ALPP (< 60 cm water) has been associated with ISD.'''
** '''Most forms of SUI likely involve some degree of ISD, even if urethral hypermobility is present.'''
*** Even among patients with hypermobility, treatments such as pubovaginal sling, midurethral sling, and even bulking agents appear to have reasonable efficacy.
** '''However, the reverse is untrue— treatments aimed specifically at the correction of hypermobility may be less helpful in the presence of severe ISD and limited mobility.'''
*** '''Burch colposuspension and various needle suspension procedures, for example, have limited usefulness in the treatment of ISD, particularly in the setting of a fixed urethra.'''