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World J Urol (1997) 15:268-274 Springer-Verlag 1997

J o h n O . L . D e L a n c e yT h e p a t h o p h y s i o l o g y o f s t r e s s u r i n a r y i n c o n t i n e n c e i n w o m e na n d i t s i m p l i c a t i o n s f o r s u r g i c a l t r e a t m e n t

Abstract S t r e s s u r i n a r y i n c o n t i n e n c e i s a s y m p t o m t h a ta r i s e s f r o m d a m a g e t o t h e m u s c l e s , n e r v e s , a n d c o n -n e c t i v e t is s u e o f t h e p e l v i c f l o o r . U r e t h r a l s u p p o r t , v e -s ic a l n e c k f u n c t i o n , a n d f u n c t i o n o f t h e u r e t h r a l m u s c l e sa r e i m p o r t a n t d e t e r m i n a n t s o f c o n t in e n c e . T h e u r e t h r a iss u p p o r t e d b y t h e a c t i o n o f th e l e v a t o r a n i m u s c l est h r o u g h t h e i r c o n n e c t i o n t o t h e e n d o p e l v i c fa s c i a o f t h ea n t e r i o r v a g i n a l w a ll . D a m a g e t o t h e c o n n e c t i o n b e -t w e e n t h i s f a s ci a a n d m u s c l e , l o ss o f n e r v e s u p p l y t o t h em u s c l e , o r d i r e c t m u s c l e d a m a g e c a n i n f l u e n c e c o n t i -n e n c e . I n a d d i t i o n , l o ss o f n o r m a l v e s ic a l n e c k c l o s u r ec a n r e s u l t i n i n c o n t i n e n c e d e s p i t e n o r m a l u r e t h r a l s u p -p o r t . A l t h o u g h t h e t r a d i t i o n a l a t t i t u d e h a s b e e n t o i g -n o r e t h e u r e t h r a a s a f a c t o r c o n t r i b u t i n g t o c o n t i n e n c e ,i t d o e s p l a y a r o l e i n d e t e r m i n i n g s t r e s s c o n t i n e n c e s i n c ei n 5 0 % o f c o n t i n e n t w o m e n , u r i n e e n t e rs t h e u r e t h r ad u r i n g i n c r e a s e s i n a b d o m i n a l p r e s s u r e , w h e r e i t i ss t o p p e d b e f o r e i t c a n e s c a p e f r o m t h e e x t e r n a l m e a t u s .P e r h a p s o n e o f t h e m o s t i n t e r e s t i n g y e t l e a st a c k n o w l -e d g e d a s p e c t s o f c o n t i n e n c e c o n t r o l c o n c e r n s t h e c o o r -d i n a t i o n o f th i s s y st e m . T h e m u s c l e s o f th e u r e t h r a a n dl e v a t o r a n i c o n t r a c t d u r i n g a c o u g h t o a s s is t c o n t i n e n c e ,a n d l it tl e i s k n o w n a b o u t t h e c o n t r o l o f th i s p h e n o m e -n o n . T h a t o p e r a t i o n s c u r e s tr e ss i n c o n t i n e n c e w i t h o u ta l t e r i n g n e r v e o r m u s c l e f u n c t i o n s h o u l d n o t b e m i s i n -t e r p r e t e d a s i n d i c a t i n g t h a t t h e s e f a c t o r s a r e u n i m p o r -t a n t .

John O. L. DeLanceyDepartment of Obstetrics and Gynecology,University o f Michigan M edical School,Ann Arbor, Michigan, USAJ. O. L. DeLancey ([~)D2234 Medical Professional Building,1500 East Medical Center Drive,Ann Arbor, MI 48109-0718, USATel.: + 1-313-764-1195; Fax : + 1-313-764-7261E-mail: DeLancey@um ich.edu

T h i s a r t i c l e c o n s i d e r s o u r b i o l o g i c a l u n d e r s t a n d i n g o ft h e u r i n a r y c o n t i n e n c e m e c h a n i s m a n d e x p l o r e s w h a tt h i s k n o w l e d g e t e l l s u s a b o u t o u r c u r r e n t s u r g i c a l a p -p r o a c h t o s t r e s s u r i n a r y i n c o n t i n e n c e .

Histor ica l backgroundP r o g r e s s h a s b e e n m a d e d u r i n g t h i s c e n t u r y i n t h e s u r -g i ca l t r e a t m e n t o f st r es s u r i n a r y i n c o n t i n e n c e . K e l l y a n dD u m m [ 1 5] n o t i c e d t h a t t h e v e s ic a l n e c k f a i l e d t o c l o sep r o p e r l y i n m a n y w o m e n w i t h s e v er e s tr e ss i n c o n t i n e n c ea n d u s e d s i l k s u t u r e s t o n a r r o w t h e v e s i c a l n e c k i n a t -t e m p t s t o c u r e th i s p r o b l e m . A f e w y e a r s l at e r , B o n n e y[ 1 ] c a l l e d a t t e n t i o n t o u r e t h r a l s u p p o r t l o s s i n s t r e s s -i n c o n t i n e n t w o m e n a n d p l i c a t e d t h e f a s c i a u n d e r n e a t ht h e v e s ic a l n e c k t o c o m p e n s a t e f o r t h i s l o ss o f u r e t h r a ls u p p o r t . I n t h e l a t e 1 9 4 0 s , M a r s h a l l e t a l . [ 1 7 ] r e p o r t e da n e m p i r i c a l o b s e r v a t i o n t h a t i f th e p e r i u r e t h r a l t i ss u e sw e r e s u t u r e d t o t h e p u b i c b o n e , s t r e s s i n c o n t i n e n c ec o u l d b e a l le v i a te d . T h e y h a d n o o b s e r v a t i o n c o n c e r n i n gt h e c a u s e o f st r es s i n c o n t i n e n c e a n d w a r n e d t h a t t h es u c ce s s o f t h e i r s u r g e r y s h o u l d n o t b e u s e d t o c o n f i r ma n y p a r t i c u l a r t h e o r y a b o u t t h e c a u s e o f s tr e ss u r i n a r yi n c o n t i n e n c e . D e s p i t e t h i s a d m o n i t i o n , c o m m o n p r a c t i c eh a s b e e n t o u s e t h e s u c c es s o f s t r e ss i n c o n t i n e n c e s u r g e r yt o m a k e i n f e r e n c e s a b o u t c o n t i n e n c e b i o lo g y .

I n t h e l a t e 1 9 7 0 s t h e n a t u r e o f u r e t h r a l s u p p o r t l o s sw a s c l a r i f i e d b y R i c h a r d s o n e t a l. [ 25 ], w h o i d e n t i f i e d th ej u n c t i o n o f th e p a r a v a g i n a l e n d o p e l v i c f a sc i a w i t h th ea r c u s t e n d i n e u s a t t h e p e l vi c w a l l a s th e a n a t o m i c l o c a -t i o n w h e r e t h e u r e t h r a l s u p p o r t s f a i l e d . R e a t t a c h m e n t o ft h e d e t a c h e d p a r a v a g i n a l t i s s u e s t o t h e a r c u s t e n d i n e u sa l l e v i a t e d s t r e s s i n c o n t i n e n c e i n th o s e w o m e n w h o s e s t r e s si n c o n t i n e n c e w a s c a u s e d b y p a r a v a g i n a l d e f e c t . A t a b o u tt h e s a m e t i m e , M c G u i r e e t a l . [ 1 9 ] c a l l e d a t t e n t i o n t o t h ei m p o r t a n c e o f d e t er m i n i n g w h e t h e r a w o m a n ' s s tr e ssi n c o n t i n e n c e w a s c a u s e d b y d e f e c t i v e ve s ic a l n e c k

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269function or abnormal support. They observed that agroup of women existed whose stress incontinence wascaused not by loss of urethral support but because ofinadequate vesical neck closure and that these individ-uals constituted an important class of women whofailed typical support operations for stress incontinence.These two observations suggested that treatment ofstress-incontinent women should be based on the typeof damage present rather than being the same for allwomen.These observations have contributed significantly toour clinical managemen t of stress urinar y incontinence.As yet, however, the na ture of incontinence defects havenot yet been tested using the scientific method. Duringthe same period in which these clinical observations havebeen made, data have been accumulating concerningchanges in the pelvic muscle, nerve, and connective tis-sue. This article evaluates scientific observations of thestress-continence control system, considers the types ofdamage that manifest in women with stress inconti-nence, and evaluates how our treatment of stress in-continence might benefit from emerging informationabout the neuromuscular and fascial abnormalities thatexist in incontinent women.This remains a relevant exercise despite reports in theliterature suggesting a high degree of success with sur-gery. Not only is there some question about whetherthese high success rates might be completely accuratebut, in addition, these operations sometimes create newproblems that leave some women cured of their stressincontinence but burdened with a new problem such asdifficult voiding, de trusor instability, or enterocele.

Stress-cont inence control system

Nature of urethral supportA lateral view of the pelvic organs displayed in Fig. 1reveals the relevant anatomy of the continence controlsystem [8]. It should be noticed that some structureshave been cut away to reveal elements contributing tocontinence. The important components to be noticedfirst are the levator ani muscles, which run from thepubic bone to the anal sphincter and behind the rectumin a position where they can support the pelvic organs.These muscles lie lateral to the arcus tendineus fasciaepelvis, a band of endopelvic fascia that stretches betweenthe public bone and the ischial spine. It should also benoticed how the endopelvic fascia unties the anteriorvaginal wall (shown throug h a window cut in the lateralvaginal wall) to the arcus tendineus.The layer formed by the anterio r vaginal wall and itsconnection to the arcus tendineus fasciae pelvis by theendopelvic fascia forms a hammock-like layer in whichthe bladder and vesical neck rest [8]. Although this fas-cial support is usually thought to be a passive ratherthan an active mechanism, the connection between thefascia and the levator ani muscle is an importa nt elementof this system [7, 10]. This connection permits activecontraction of the pelvic muscles to elevate the vesicalneck and their relaxation to allow it to descend [21]. Inaddition, the normal constant activity of the levator animuscles [23] supports the vesical neck du ring normalactivities. It is my opinion that the role of the neuro-muscular control of the urethral and levator ani musclesas well as their attachments to the urethral supportivetissues will likely prove to be one of the major deter-minants of urinary continence.

Surgery for stress urinary incontinence is effective ineliminating incontinence during increases in abdominalpressure. It does not, however, restore normal physiol-ogy. The continence mechanism comprises an elegantlyorgan ized series of nerves, muscles, and connective tissuethat dynamical ly influence bladder control. Thisarrangement allows prompt and complete bladderemptying while also maintaining continence during tre-mendous increases in abdominal pressure.The very dynamic nature of this continence controlsystem is often overlooked in surgical discussions but iscritical to our complete understanding of how conti-nence is controlled. The dynamic nature of the conti-nence system is likely discounted because operations areincapable of influencing the coordination and strengthof the neuromuscular apparatus controlling continence.Therefore, a simpler view of continence is more attrac-tive to both surgeon and patient. This observationshould not be seen as a criticism of surgery for stressincontinence because operative therapy has proved to beremarkably effective despite its empirical nature. Pro-gress, however, may result from a better understandingof the specific mechanism of continence.

En~ g ~ ~ / ~ o~ . . A rcusted.n ~ ) " ~ A rc us tend.~ ! ~ ~ . f A . ~?: / fasc.pelv.RectumJ ~ ~ 4 ~ / Levator ni

Externalanal ~ ~ ~ ~ Urethras p h i n c t e r ~ ~ ~0"//'~"--"="~ -- . .- .~ _ r~ / ' - Perineal- ~ membraneFig. 1 Lateral view of the continence mechanism, showing theattachments of the endopelvic fascia to the arcus tendineus fasciaepelvis (Arcus tend. asc. p elv. ) and to the levator ani muscles [8]

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270i t aga ins t an unde r ly ing s idewa lk . I f , however , the laye ru n d e r t h e u r e th r a b e c o me s u n s t a b l e a n d d o e s n o t p r o -v ide a f i rm backs top aga ins t which abdomina l p re ssurecan compress the ure thra , the oppos ing force tha t causesc losure i s los t and the occ lus ive ac t ion i s d imin ished . Thela t te r s i tua t ion i s s imi la r to tha t in which one t r ie s tos to p t h e f l o w o f w a t e r t h r o u g h a g a r d e n h o s e b y s t e p p i n gon i t while i t l ies on sof t soil .

This ana log y could he lp us expla in why some pa t ien tsw h o h a v e a l a rg e c y s to - u r e th ro c e l e a n d i n w h o m th eu r e th r a i s f a r b e lo w i ts n o r ma l p o s i t i o n mi g h t n o n e th e -less be cont inen t . I f th i s subure th ra l laye r e s tab l i shes i tsstabil i ty, a lbeit a t a lower level , this mechanism couldrem ain effective (Fig. 3) .

Fig. 2 View of the urethra and vagin a, cut in cross section ust b elowthe vesical neck demonstrating how abdom inal pressure (arrow) cancompress the urethra against the un derlying fascia [8]

A re levant ques t ion a s ye t unanswered i s the fo l low-ing : how does th is appa ra tus keep the ure thra c losedt igh t ly enough tha t inc reases in ves ical p re ssure dur ing af o r c e fu l c o u g h d o n o t f o r c e u r in e o u t t h r o u g h t h e u r e -thra ( i . e . , to ma in ta in the pos i t ive pre ssure grad ien twhere the ure thra l c losure pre ssure i s g rea te r than theb ladde r pre ssure ) . Some pre l imina ry ins igh t in to th isq u e s t i o n c a n b e g a i n e d b y e x a min a t i o n o f a n a to micspec imens us ing s imula ted inc reases in abdomina l p re s -sure. This v iew revea ls tha t the ure th ra l ie s in a pos i t i onwhere i t can be compressed aga ins t the suppor t ingham mo ck by r i se s in abdom ina l p re ssure (F ig . 2 ) [8 ] . Incons id e ra t ion of th is laye r i t should be r ecognized tha t innorma l women the an te r io r vag ina l wa l l i s in contac twi th the pos te r io r vag ina l wa l l , and fur the r work wi l l beneeded to e s tab l i sh the r e la t ive cont r ibu t ions of thesewa l l s to u re thra l suppor t .In th is conceptua l mode l i t i s the s tab i l i ty o f theses u p p o r t i n g l a y e r s r a th e r t h a n t h e h e i g h t o f t h e u r e th r atha t de te rm ines s t r ess cont inence . In an ind iv idua l wi th af i r m s u p p o r t i v e l a y e r t h e u r e th r a w o u ld b e c o mp r e s s e dbe tween abdomina l p re ssure and pe lv ic f a sc ia in muchthe same way tha t on e can s top the f low of wa te rt h r o u g h a g a r d e n h o s e b y s t e p p in g o n i t a n d c o mp r e s s in g

C o o r d i n a t i o n p r o b l e m sThe e ssence of th is u re thra l suppor t concept i s i t s mul-t i f ace ted na ture . The re i s no s ing le s t ruc ture tha t p ro-v i de s u r e th r al s u p p o r t , b u t r a t h e r s u p p o r t i s p r o v id e d b ythe coord in a ted ac t ion of f a sc iae and musc le s und e rneura l cont ro l ac t ing a s an in tegra ted un i t . The pe lv icmusc le s a re known to cont rac t dur ing inc reases inabdomina l p re ssure , ind ica t ing the i r po ten t ia l pa r t ic i -pa t ion in prevent ing ur ina ry loss . Changes in pe lv icne rve func t ion have a lso been shown to be a ssoc ia tedwi th s t r e ss incont inence , and th is may inf luence cont i -nence by re su l t ing in weake r musc le s o r th rough loss o fmusc le coord i na t ion . In addi t io n , even i f the musc le andi ts ne rve supply i s in tac t a pa t ien t might have a de fec t inth e c o n n e c t i o n b e tw e e n t h e f a s c ia s u p p o r t i n g t h e u r e th r as u c h t h a t mu s c u l a r c o n t r a c t i o n i s me c h a n i c a l l y u n c o u -p l e d f r o m u r e th r a l s u p p o r t . D a ma g e t o a n y e l e me n t o fthe s t r e ss -cont inence cont ro l sys tem might le ssen awomen 's ab i l i ty to r ema in cont inen t dur ing inc reases ina b d o min a l p r e s s u r e . Re c e n t o b s e r v a t i o n s i n o u r u n i td e mo n s t r a t e t h a t c e r t a i n s t r e s s - i n c o n t i n e n t w o me n c a nsignif icantly decrease inco ntin ence in a single visi t s implyby lea rn ing to cont rac t the i r pe lv ic musc le s in an t ic ipa -t ion o f a coug h [20]. In these women the musc le s havenot becom e s t ronge r , nor have conne c t ive ti s sues hea led .These ind iv idua ls have s imply rec rea ted the norma l co-o r d i n a t i o n o f p e lv i c mu s c l e c o n t r a c t i o n t h a t t h e y p r e -sumably had los t . More r e sea rch wi l l be needed to

Fig. 3 A. Diagram showingabdominal pressure closing theurethra against the underlyingurethral supports. B. In thisdiagram the supporting tissuesare unstable and do not form afirm layer against which theurethra can be compressed. C.A cystourethrocele in whic h theurethra is much lower thannormal but has a strong sup-portive layer that allows ure-thral compression [8]

A B C

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d e t e r m i n e h o w m a n y w o m e n w i t h s t r e s s i n c o n t i n e n c el a c k th i s n o r m a l p r e c o n t r a c t i o n o f t h e p e lv i c m u s c l e sa n d w h i c h w o m e n c a n r e p r o g r a m t h e ir p e lv i c m u s c le s t oa c h i e v e c o n t i n e n c e .

S p h i n c t e r p r o b l e m s : v e s i c a l n e c k a n d u r e t h r aI n a d d i t i o n t o l o w e r - u r i n a r y - t r a c t s u p p o r t , v e s ic a l n e c ka n d u r e t h r a l s t r u c t u r e s h o u l d a l s o c o n t r i b u t e t o c o n t i -n e n c e . T h e t e r m vesical neck i s a r e g i o n a l a n d f u n c t i o n a lo n e a s p r e v i o u s l y d i s c u s s ed a n d d o e s n o t r e f e r to a s i n g lea n a t o m i c e n t i ty . I t d e n o t e s t h a t a r e a a t t h e b a s e o f th eb l a d d e r w h e r e t h e u r e t h r a l l u m e n p a s s e s t h r o u g h t h et h i c k e n e d m u s c u l a t u r e o f t h e b l a d d e r b a s e . I t h a s c o m et o b e c o n s i d e re d s e p a r a t el y f r o m t h e b l a d d e r a n d u r e t h r ab e c a u s e t h e r e a r e s o m e u n i q u e f u n c t i o n a l c h a r a c t e r i s t i c so f t h i s a r e a . S p e c i f i c a l ly , l o s s o f a d r e n e r g i c s t i m u l a t i o no r d a m a g e t o t h i s a r e a r e s u l t s i n i t s f a i l u r e t o c l o s ep r o p e r l y , a n d w h e n t h is i s t h e c a u s e o f st r es s i n c o n t i -n e n c e , s i m p l e u r e t h r a l s u s p e n s i o n i s o f t e n i n e f f e c ti v e i nc u r i n g t h i s p r o b l e m [ 1 8 ] .S o m e p l a u s i b l e h y p o t h e s i s a s t o w h y p o o r v e s i c a ln e c k c l o s u r e m i g h t i n f l u e n c e c o n t i n e n c e i s n e e d e d . A l -t h o u g h d i f fi c u lt t o p r o v e , i t s e e m s l ik e l y th a t t h e c h a n g ei n b l a d d e r - b a s e s h a p e m a y b e i n f l u e n t i a l [ 1 4 ] . I n c r e a s e df l u i d p r e s s u r e i n a c o n t a i n e r a c t s p e r p e n d i c u l a r l y t o t h ew a l l s . W h e n t h e b l a d d e r b a s e i s f l a t t h i s p r e s s u r e t e n d sn o t t o d i l a t e t h e b l a d d e r . H o w e v e r , w h e n f u n n e l i n g o c -c u r s , t h e n a n w e d g e - s h a p e d b o l u s o f u r i n e e x i st s t h a t c a nd r i v e t h e u r e t h r a o p e n d e s p i t e i ts n o r m a l s u p p o r t . T h a tc o l l a g e n i n j e ct i o n , w h i c h c h a n g e s t h e s h a p e o f t h e v e s ic a ln e c k l u m e n b u t n o t t h e c l o s u r e p r e s s u r e, a l l e v i at e s s tr e s si n c o n t i n e n c e i s c o n s i s t e n t w i t h t h is h y p o t h e s i s .U r e t h r aC o m m o n p r a c t ic e h a s b e e n to d i s c o u n t t h e u r e t h r a 's r o l ei n m a i n t a i n i n g c o n t i n e n c e b e c a u s e u r e t h r a l s u s p e n s i o nc u r e s i n c o n t i n e n c e w i t h o u t c h a n g i n g t h e u r e t h r a l c l o s u r ep r e s s u r e . T h e c r e a t i o n o f a n a r t i f ic i a l c o n t i n e n c e m e c h -a n i s m , h o w e v e r , d o e s n o t a l l o w u s t o m a k e c o n c l u s i o n sa b o u t n o r m a l c o n t i n e n c e , a n d s e v e r a l o b s e r v a t i o n ss u p p o r t t h e c o n c e p t t h a t t h e u r e t h r a d o e s p l a y a r o l e i nc o n t i n e n c e . F i r s t , w o m e n w i t h s t r e s s i n c o n t i n e n c e h a v el o w e r u r e t h r a l c l o s u r e p r e s s u r e s ( 34 c m H 2 0 ) a s c o m -p a r e d w i t h a g r o u p o f a g e - m a t c h e d c o n t i n e n t w o m e n( 68 c m H 2 0 ) [ 13 ]. S e c o n d , e x c i s io n o f t h e d i s ta l u r e t h r ac a n c r e a t e s t r e s s i n c o n t i n e n c e i n p r e v i o u s l y c o n t i n e n tw o m e n [ 24 ]. T h i r d , i n 5 0 % o f c o n t i n e n t w o m e n , u r i n ep a s s e s t h e l e v e l o f t h e v e s i c a l n e c k i n r e s p o n s e t oc o u g h i n g , o n l y t o b e r e t u r n e d t o t h e b l a d d e r b y t h eu r e t h r a l m u s c u l a t u r e [ 2 9 ] . A l t h o u g h w o m e n w h o a r ec o n t i n e n t a t t h e v e s i c a l n e c k d o n o t n e e d u r e t h r a lf u n c t i o n t o r e m a i n d r y , t h o s e i n w h o m u r i n e p a s s e sb e y o n d t h i s le v e l d o .

T h e u r e t h r a i s a c o m p l e x t u b u l a r v i sc u s e x t e n d i n gb e l o w t h e b l a d d e r . E m b e d d e d w i t h i n i t s s u b s t a n c e a r e a

271Table 1 To pog rap hy of urethral and p araurethral structures ~'bApproximate Region of the urethra P araurethral s tructureslocation

0-20 Intramural urethra Urethral lumen traversesthe bladder wall20-60 Midurethra Sphincter urethrae musclePubovesical muscleVaginolevator attachement60-80 Perineal memb rane Com pressor urethraemuscleUrethrovaginal sphinctermuscle80-100 Distal urethra Bulbocavemosus muscle

a Smooth m uscle of the urethra was not consideredb Expressed as percentage o f the total urethral lengthReprinted with permission from the A merican Co llege of Ob-stericians and Gyne cologists [8]

n u m b e r o f el e m e n ts t h a t a r e i m p o r t a n t t o l o w e r - u r in a r y -t r a c t d y s f u n c t i o n . T h e i r l o c a t i o n s a r e s u m m a r i z e d i nT a b l e 1 [6 ] . B o t h t h e m u s c l e o f t h e s t r i a t e d u r o g e n i t a ls p h i n c t e r m u s c l e a n d t h e s m o o t h m u s c l e a c t t o c o n s t r i c tt h e u r e t h r a l l u m e n [ 2 6] . T h e s e s t r u c t u r e s n o t o n l y d i-m i n i s h w i t h a g e [ 5] b u t a l so s h o w e v i d e n c e o f d e n e r v a -t i o n i n j u r y [ 1 1 ] .

I n n e r v a t i o nR e c e n t s t u d i e s h a v e d e m o n s t r a t e d a l t e r a t i o n s i n p u -d e n d a l n e r v e f u n c t i o n i n w o m e n w i t h s t r e s s u r i n a r y i n -c o n t i n e n c e [ 2 7 , 2 8 ] . A t p r e s e n t i t i s u n c l e a r w h y t h i sn e u r o p a t h y r e s u lt s in d e c r e a s e d c o n t in e n c e . T h e s t r e n g t ho f t h e a s s o c i a ti o n b e t w e e n s t re s s i n c o n t i n e n c e a n d n e u -r o p a t h y , h o w e v e r , s u g g e s t s t h a t i t s h o u l d b e s e r i o u s l yc o n s i d e r e d . N e r v e d a m a g e m i g h t c h a n g e s e v e r a l t h i n g sa b o u t t h e c o n t i n e n c e m e c h a n i s m , r e s u l ti n g in d e c r e a s e dr e s e rv e . L o s s o r w e a k e n i n g o f l e v a t o r a n i m u s c l e c o n -t r a c t i o n d u r i n g a c o u g h c o u l d d e s t a b i l i z e t h e s u p p o r t i v el a y e r a n d p r e v e n t a b d o m i n a l p r e s s u r e f r o m b e i n g c a -p a b l e o f c o m p r e s s i n g t h e u r e t h r a a g a i n s t t h e e n d o p e l v i cf a s c i a . I n a d d i t i o n , d e c r e a s e s i n u r e t h r a l c l o s u r e p r e s s u r ew o u l d d i m i n i s h t h e p r e s s u r e d i f f e re n t i a l t h a t n e e d b eo v e r c o m e t o c a u s e i n c o n t i n e n c e . S p e c if i c t e s ti n g o f t h e seh y p o t h e s e s w i ll b e n e e d e d t o d e t e r m i n e w h e t h e r t h e y a r er e l e v a n t a n d h o w f r e q u e n t l y t h e y o c c u r as a c a u s e o fi n c o n t i n e n c e .T h e r e a r e s e v e r a l l e v e l s a t w h i c h t h e c o n t i n e n c em e c h a n i s m c a n f a il . T h e e n d o p e l v i c f as c i a m a y d e t a c hf r o m i ts l a te r a l a t t a c h m e n t s ( p a r a v a g i n a l d e f e c t ) a n d t h i sm a y i n v o l v e t h e l e v a t o r a n i m u s c l e s . T h e n o r m a l n e u r a lc o n t r o l o f th e m u s c l e m a y b e lo s t s u c h t h a t c o n t r a c t i o nc a n n o t o c c u r , o r i t m a y n o t b e a c t i v a t e d a t t h e r i g h tt i m e . T h e v e s i c al n e c k m a y f a i l t o c l o s e a n d t h e u r e t h r am a y n o t h a v e s u f f i ci e n t c o n s t r i c t i o n t h a t i t c a n k e e pu r i n e f r o m e s c a p i n g o n c e t h e v e s i c a l n e c k h a s b e e nt r a n s g r e ss e d . I t i s l i k el y t h a t m o s t w o m e n h a v e a c o m -b i n a t i o n o f d e f ec t s a n d t h a t s o r t i n g t h e m o u t w i l l r e q u i r el a r g e s t u d ie s o f i n c o n t i n e n t a n d c o n t i n e n t w o m e n .

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272W i l l i t m ake any d i f fe rence to unders tand the de ta i l so f how the cont i nence m echan i sm works?One wonders whether a better understanding of conti-nence physiology could lead to improved treatmentoutcomes for incontinent women. Why would a changefrom empirically based treatment to therapy directed atan exact understanding of the defects involved in in-continence make a difference? The following story [9] isprovided to call attention to the difference betweenempirically based treatments as currently used and thosebased on knowledge of the specific nature of an indi-vidual's injury.Imagine that you have fallen, twisting your left legawkwardly beneath you. As you get up you find thatyour leg is difficult to control and that the knee seemsunstable. An orthopedic surgeon examines your leg inthe emergency room, confirms that your knee movesabnormally, and diagnoses genu i n s t ab i l i cus . He suggestsan operation to fuse your knee permanently in a straightposition to eliminate the instability.The problems with this approach are immediatelyapparent. First, an accurate anatomic diagnosis has notbeen made. Is the cartilage torn? Is collateral ligamentruptured? Did the quadriceps tendon avulse from thepatella? Might you have injured a nerve that has alteredmuscular control? In consideration of these questions itis apparent that the physician's diagnosis has simplyreiterated your symptoms in a medical-sounding phrase.It has not established what is wrong with the anatomiccomponents of the knee. In addition, an operation hasbeen planned that may solve the instability but willdisrupt normal function. The surgeon may be quitesatisfied that your knee does not wobble after the op-eration, but you may not be happy hobbling around ona stiff leg.As obvious as the problems with this scenario are, thediagnostic and therapeutic approach it illustrates is un-comfortably close to the current diagnosis and tr eatmentof stress u rina ry incontinence. A woma n seeking care forincontinence who says she is wet when she coughs,sneezes, or performs activities that increase abdominalpressure is examined, tested, and told she has stressurinary incontinence. This gives a name to the symptomsshe has provided. It does not, however, say anythingabout the actual damage that has occurred, be it neu-rologic, ligamentous, or muscular. Treatment is some-times instituted irrespective of the specific anatomiclesion involved. If surgery is proposed, it may cure theincontinence but may lead to loss of other normal uri-nary tr act function in the form of difficulty with normalurination [16], new detrusor instability [4], or pelvic or-gan prolapse in the form of an enterocele [30]. Alter-natively, pelvic muscle exercise may be prescribed, whichhelps many (but by no means all) women, and is im-plemented regardless of whether a patient has intactinnervation to her pelvic floor muscles or whether themuscles have become detached from their connections.

Pelvic-muscle exerciseOne definite way in which an understanding of thespecific continence-system injuries might improve ourtreatment concerns the effectiveness of pelvic muscleexercise. Women with stress urinary incontinence areoften told to perform pelvic muscle exercise to improvetheir continence. An individual who has sustained sig-nificant denervation at the time of vaginal birth and whohas lost all control of her pelvic muscles could not beexpected to improve any more than paraplegics could beexpected to improve their leg-muscle strength. Since halfof women treated with muscle strengthening fail to re-duce their wetting episodes by 50% and only about onein six is dry [3], the question as to why this treatment isvariably effective arises.A woman who has lost the nerve supply to the pelvicmuscles will not succeed in improving continence withpelvic muscle exercise. Similarly, a women whose mus-cles have been torn from their normal attachments mightnot be expected to get better. On the other hand, dra-matic improvements in continence occur in women whohave lost the normal unconscious activation of the pelvicmuscles during a cough but are capable of learning thatskill. Women whose muscles contract normally but aretoo weak to maintain continence can exercise theirmuscles such that the latter become strong enough towithstand the forces placed on them.Precision in patient selection might improve the suc-cess of pelvic muscle education without changing theregimens used. If we can exclude as inappropriate can-didates for this mode of therapy all women who havelost the nerve supply to the muscles and those in whomurethral supports have become disconnected from themuscles, then the success of the pelvic-muscle skill in-struction and pelvic muscle strengthening will rise.Women destined from the start to fail muscle trainingbecause of their anatomic or functional abnormalityshould be triaged into other effective therapy and savedthe frustration and expense of trying something theycannot do.

Voiding parado xAnother way in which an understanding of the dynamicnature of continence helps us to understand clinicalproblems concerns postoperat ive voiding difficulties seenin women whose urethras are sewn immovably to bone.There is an ironic paradox between the concept of nor-mal continence control and the operations for stressincontinence. Many women void by increasing abdo-minal pressure to facilitate bladder emptying. Althoughthis is not a normal mechanism, it is quite commonlyused and is responsible for a voiding mechanism in ap-proximately one-fourth of stress-incontinent women.This is accomplished through relaxation of the pelvicfloor musculature, which puts the continence mechanism

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273i n a c o n f i g u r a t i o n i n w h i c h i n c r e a s e s i n a b d o m i n a lp r e s s u re f a v o r e m p t y i n g .

O p e r a t i o n s d o n o t c h a n g e t h e r e s t i n g u r e t h r a l p r e s -s u r e. T h e g o a l o f s t r e ss i n c o n t i n e n c e s u r g e r y i s t o c r e a t ep e r f e c t p r e s s u r e t r a n s m i s s i o n , w h e r e i n c r e a s e s i n a b d o -m i n a l p r e s s u r e a r e c o u n t e r e d b y e q u a l o r g r e a t e r i n -c r e a s e s in u r e t h r a l c l o s u r e p r e s s u r e . T h e r e f o r e , i f a no p e r a t i o n a c h i e v e s s u c c e s s b y p e r m a n e n t l y f i x i n g t h eu r e t h r a i n p l a c e w h e r e p r e s s u r e t r a n s m i s s i o n i s p e r f e c t ,t h a t w o m e n l o s e s t he a b i l i ty t o v o i d o r to a u g m e n t u r i -n a t i o n b y th e V a l s a l v a m a n e u v e r . I n w o m e n w h o h a v ep r e v i o u sl y v o i d e d b y t h e V a l s a l v a m a n e u v e r t h e d e t r u s o rm u s c l e m u s t b e r e a w a k e n e d t o c o n t a c t b e f o re c o m p l e t ee m p t y i n g c a n o c c u r . I f t h e r e i s s u f f ic i e n t n e r v e l o s s t o t h ed e t r u s o r m u s c l e t h a t i t c a n n o t b e c a l le d i n to a c t i o n , t h e ns p o n t a n e o u s v o i d i n g c a n n o t o c c u r . I n t h e s e i n d i v id u a l st h e r e a r e o n l y t w o p o s s i b il i t ie s : s o m e s t r e s s i n c o n t i n e n c ea n d t h e a b i li t y t o e m p t y t h e b l a d d e r b y t h e V a l s a l v am a n e u v e r o r n o s t r e ss in c o n t i n e n c e a n d t h e n e e d fo ri n t e r m i t t e n t s e l f - c a t h e t e r i z a t i o n . T h i s h i g h l i g h t s t h e i m -p o r t a n c e o f th e d y n a m i c n a t u r e o f th e c o n t i n e nc em e c h a n i s m a n d i t s a b i l i t y t o s w i t c h b e t w e e n p r e s s u r et r a n s m i s s i o n a n d v o i d i n g f u n c t i o n . T h a t t h i s is u n d e rm u s c u l a r c o n t r o l i s s u p p o r t e d b y B u m p e t a l. 's o b s e r-v a t i o n s [2] t h a t p r e s s u r e t r a n s m i s s i o n i s d e c r e a s e d w h e nt h e m u s c l e s o f t h e p e l v ic f l o o r a r e p a r a l y z e d .

s i n c e s o m e s t u d i e s f a i l t o r e v e a l a d i f f e r e n c e b e t w e e nu r e t h r a l s u p p o r t i n s t r e s s - c o n t i n e n t a n d s t r e s s - i n c o n t i -n e n t w o m e n [ 12 ]. T h e r e i s a r e a l a n d c o n s i s t e n t d i f f e r -e n c e in t he a v e r a g e m a x i m a l u r e t h r a l c l o s u r e p r e s s u r em e a s u r e d i n i n c o n ti n e n t a n d c o n t i n e n t w o m e n , y e t th eu r e t h r a h a s l a r g e l y b e e n ig n o r e d a s p a r t o f t h e p a t h o -p h y s i o l o g y [ 1 3 , 2 8 ] . T h i s r e m a r k a b l e r e s i s t a n c e t o t h ea c c e p t a n c e o f s ci e nt if ic d a t a l ik e l y c o m e s f r o m s u r g e o n s 'd e s i re t o b e l i e ve t h a t t h e y a r e r e c r e a t i n g t h e n o r m a l . I t ish a r d f o r u s to a c c e p t t h a t o u t o p e r a t i o n s f o r s tr e s s i n -c o n t i n e n c e a r e e m p i r i c a l a n d b y p a s s t h e n o r m a l c o n t i -n e n c e m e c h a n i s m . R e c o g n i t i o n t h a t o p e r a t i o n s c r e a t e an e w f o r m o f c o n t in e n c e s h o u l d n o t m a k e u s a n y l e sse n t h u s i a s t i c a b o u t t h e i r e ff e c ti v e n es s . T h a t a g a s t r i c e x -c l u s i o n o p e r a t i o n c o r r e c t s o b e s i t y d o e s n o t s u g g e s t t h a ta n a b n o r m a l l y l a r g e s t o m a c h i s r e s p o n s i b l e f o r o b e s i t y ,n o r d o e s t h e f a i l u r e o f th i s s u r g e r y t o a d d r e s s t h e c e l l u la ra n d b e h a v i o r a l p r o b l e m s i n v o l v e d i n o b e s it y m a k e t h eo p e r a t i o n a n y l e s s e f fe c t iv e . W e m u s t b e g i n t o a c c e p t t h ee m p i r i c a l n a t u r e o f o u r o p e r a t i o n s a n d r e c o g n i z e b o t ht h e i r a d v a n t a g e s a n d t h e i r d i s a d v a n t a g e s . T h i s w il l l e a du s t o a p r o p e r r e c o g n i t i o n o f t h e d a m a g e e x i s ti n g ini n d iv i d u al w o m e n a n d t o w a r d t h e s e le c ti o n o f t r e a t m e n tt h a t i s a p p r o p r i a t e f o r t h e d a m a g e p r e s e n t .

Re fe re nc e sIs a bs olute c ont ine nc e a re a l is t ic goa l?T h e a s s u m p t i o n o f t h e s u r g ic a l l it e r a t u r e t h a t a b s o l u t es t re s s c o n t i n e n c e u n d e r a l l c i r c u m s t a n c e s i s r e q u i r e d f o ra n o p e r a t i o n t o b e j u d g e d e f f ec t iv e i s a g a i n s t n o r m a lc o n t i n en c e p h y s i o l o g y . A p p r o x i m a t e l y 4 0 % o f h e a l t h yn u l l ip a r o u s w o m e n a r e in c o n t i n e n t d u r i n g v i g o r o u s e x-e r c i s e [ 2 2 ] ; t h e r e f o r e , a t t e m p t s t o c r e a t e c o n t i n e n c em e c h a n i s m t h a t i s p r o o f a g a i n s t t h e se s t r es s es m e a n st h a t w e w i ll h a v e t o i m p r o v e u p o n t h e n o r m a l c o n t i -n e n c e m e c h a n i s m . O u r o n l y a b i l it y to d o t h is w o u l d b et o d i s t o r t t h e c o n t i n e n c e m e c h a n i s m a b n o r m a l l y s u c ht h a t i t be p e r m a n e n t l y i n a s t a t e o f c o n t i n e n c e , w h i c hm e a n s t h a t w e w o u l d s a c ri f ic e v o i d i n g f u n c t i o n a t t h es a m e t i m e .

Conc lud ing thoughtsI n h is f o u r t h b o o k o f l aw s , H i p p o c r a t e s o b s e rv e d :" T h e r e a r e i n f a c t t w o t h i n g s , s c i e n c e a n d o p i n i o n ; t h ef i r s t b e g e t s k n o w l e d g e , t h e s e c o n d i g n o r a n c e " . T h i s i s ,p e r h a p s , a n o v e r ly h a r s h c o n d e m n a t i o n o f o p i n io n .F r o m o p i n i o n a n d c a r ef u l o b s e r v a t i o n s c o m e i m p o r t a n tt r u t h s t h a t a r e s u b s e q u e n t l y p r o v e d . O n t h e o t h e r h a n d ,i t e m p h a s i z e s t h a t o p i n i o n s d i ff e r a n d t h a t s c ie n c e isr e q u i r e d t o d i s t in g u i s h t h e f i r m l y h e ld p r e j u d i c e f r o m t h ef u n d a m e n t a l p r in c ip l e.

I t h a s l o n g b e e n m a i n t a i n e d t h a t s t r e s s u r i n a r y i n -c o n t i n e n c e i s c a u s e d p r i m a r i l y b y a l o ss o f u r e t h r a ls u p p o r t . I t i s c u r i o u s t h a t t h i s i d e a i s r a r e l y c h a l l e n g e d

1. Bonney V (1923) On diurnal incontinence o f urine in wom en.J Obstet Gynaecol Br Emp 30:358-3652. Bump RC, Huang KC, McClish DK, et al . (1991) Effect ofnarcotic anesthesia and skeletal muscle paralysis on passivedynamic urethral function in continent and stress incontinentwomen. Neurourol Urodyn 10:523-5323. Burns PA, Pranikoff K, Nochajski T H, H adley EC, Levy KJ,Ory M G (1993) A comparison of effectiveness of biofeedbackand pelvic muscle exercise treatment of stress incontinence inolder community-dwelling women. J Gerontol 48: M 167-M 1744. Cardo zo L D, Stanton SL, Williams JE (1979) De trusor insta-bi.lity following surgery f or ge nuine stress incontinence. Br JUro l 51:204-2075. Carlile A, Davies I, R igby A, Brocklehurst JC (1988) Agechanges in the huma n female urethra: a morp hom etric study.J Urol 139:532-5356. DeLancey JOL (1986) Correlative study of paraurethral a nat-omy. Obstet Gynecol 68:91 977. DeLancey JOL (1988) Structural aspects of the extrinsic con-tinence mechanism. Obstet Gynecol 72:296-3018. DeLancey JOL (1994) Structural support of the urethra as i trelates to stress urinary incontinence: the hammock hypothesis.Am J Obstet Gynecol 170:1713-17209. DeLa ncey JO L (1996) Stress urinary incontinence: where arew enow, where should we go? Am J Obstet Gynecol 175:311-31910. DeLa ncey JO L, Starr RA (1990) Histology o f the connectionbetween the vagina and levator ani muscles. J R eprod Med 35:765-77111. DeLancey JOL , Peschers UM , Schaer G N (1996) Discorda ntstriated muscle/connective tissue ratio in different parts of thestriated urogenital sphincter. Neurourol Urodyn 15:153-15412. Fantl JA, Hurt WG, Bump RC, Dunn LJ, Choi SC (1986)Urethral axis and sphincteric function. A m J O bstet Gynecol155:554-55813. H ilton P, Stan ton SL (1983) Ur ethra l pressure measureme nt bymicrotransducer: the results in symptom-free wome n and inthose with genuine stress incontinence. Br J Obstet Gynaecol90:919-933

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27414. Hutch JA (1967) A new theory of the anatomy of the internalurinary sphincter and the physiology of micturition. V. Thebase plate theory. Obstet Gynecol 30:309-31715. Kelly HA, Durum WM (1914) Urinary incont inence n women,without manifest injury to the bladder: a report of cases. SurgGynecol Obstet 18:444-45016. Lose G, Jorgensen L, Mortensen SO, Molsted-Pedersen L,Kristensen (1987) Voiding difficulties after colposuspension.Obstet Gynecol 69:33-3817. Marshall VF, Marchetti AA, Krantz KE (1949) The correctionon stress incontinence by simple vesicourethral suspension.Surg Gynecol Obstet 88:509-51718. McGuire EJ (1987) Urodynamic findings in patients after failureof stress incontinenceoperations. Prog Clin Biol Res 78:351 36019. McGuire EJ, Lytton B, Pepe V, Kohorn EI (1976) Stressurinary incontinence. Obstet Gynecol 47:255-26420. Miller J, Ashton-Miller JA, DeLancey JOL (1996) The knack:use of precisely P-timed pelvic muscle contraction can reduceleakage in SUI. Neurourol Urodyn 15:392-39321. Muellner SR (1951) Physiology of micturi tion. J Urol 65: 805-81022. Nygaard I, DeLancey JOL, Arnsdorf L, Murphy EM (1990)Exercise and incontinence. Obstet Gynecol 75:848 851

23. Parks AG, Porter NH, Melzak (1962) Experimental study ofthe reflex mechanism controlling muscles of the pelvic floor.Dis Colon Rectum 5:407-41424. Reid GC, DeLancey JOL, Hopkins MP, Roberts JA, MorleyGW (1990) Urinary incontinencefollowing radical vulvectomy.Obstet Gynecol 75:852-85825. Richardson AC, Lyons JB, Williams NL (1976) A new look atpelvic relaxation. Am J Obstet Gynecol 126:568 57326. Rud T, Anderson KE, Asmussen M, Hunting A, Ulmsten U(1980) Factors maintaining the intraurethral pressure inwomen. Invest Urol 17:343 34727. Smith ARB, Hosker GL, Warrell DW (1989) The role of pu-dendal nerve damage in the aetiology of genuine stress incon-tinence in women. Br J Obstet Gynaecol 96:29-3228. Snooks SJ, Badenoch DF, Tiptaft RC, Swash M (1985) Peri-neai nerve damage in genuine stress urinary incontinence. Anelectrophysiological study. Br J Urol 57:422-42629. Versi E, Cardozo LD, Studd JWW, Brincat M, O'Dowd TM,Cooper DJ (1986) Internal urinary sphincter in maintenance offemale continence. BMJ 292:166-16730. Wiskind AK, Creighton SM, Stanton SL (1992) The incidenceof genital prolapse after the Burch colposuspension. Am JObstet Gynecol 167:399-404