Concise understanding of urinary continence and incontinence

1. Concepts of continence
Dr Sumanta Mishra
Moderator: Dr Nitin S Kekre

2. Introduction
• Continence – Continentia – “ Holding back”.
• In order to maintain continence the urethral pressure must remain higher
than the intra-vesical pressure at all times except during micturition.
• ICS Definition of incontinece : “The complaint of any loss of urine “
• Prevalence – (ever, any, at least once in past 12 months) – 25 – 45%
• Incidence – 0.9 – 18 %

3. • Anatomical concept
– Bladder ncek vs mid urethra
– External sphincter vs internal sphincter
– Role of pelvic floor muscles
• Physiological correlate
• Neuro-physiology of micturition
– Central control of micturition
– Peripheral control of micturition
– Reflexes in micturition
• Hormonal influences on continence

4. Anatomical concept
• Urethral sphincter:
• The anatomy of the male urethral sphincter has not been stable since
it was first described more than 150 years ago.

5. Henle (1866) –
Urethral sphincter
composed of smooth &
skeletal muscle.
 sphincter vesicae
externus and sphincter
vesicae internus.
 Did not include muscle
around membranous
urethra

6. Holl (1897) -
 Named diaphragma
urogenital.
 Confirmed that the muscle
fibers behind the
membranous urethra end in
the Perineal Body.
 Sphincter urethrae
membranaceae joins sphincter
urethrae prostaticae and cover
the anterior surface of the
prostate.

7. Kalischer (1900) -
– Rhabdosphincter urogenitalis = skeletal urethral sphincter
– Rhabdosphincter prostaticus in a half ring formation
– Rhabdosphincter infraprostaticus completely encircling
the prostatic apex
– Rhabdosphincter diaphragmaticus,surrounds the
membranous urethra.
• in children the skeletal urethral sphincter forms a distinctly marked
muscle cap on the prostate, whereas in adults the muscle fibers are
partially atrophied and dispersed among the smooth muscles of the
prostate.

9. • Manley (1966) and Haines - Confirming the skeletal urethral sphincter
surrounds the membranous urethra in the form of an inverted horseshoe
and continues proximal over the anterolateral surface of the prostate as a
semilunar cap.
• Oelrich 1980:-
– The skeletal sphincter is formed embryologically before the
development of the prostate.
– At puberty accelerated prostate growth causes invasion and thinning
of the sphincter resulting in isolated segments of the sphincter which
partly overlap the prostate and contained within it.

10. Smooth muscle component
• Kohlrausch (1854) - first to introduce the concept of an internal sphincter
from bladder condensesation.
• Versari (1897)- internal sphincter as an anatomical entity independent of
and completely different in appearance and structure from the bladder
musculature.
• Kalischer (1900) – Internal sphincter from urethra.

11. • These findings were recently confirmed by computer generated 3-dimensional
reconstruction of the male pelvis that showed the trigone to migrate at the
bladder neck anterior to the urethra and continue down the front of the prostate
as the anterior fibromuscular stroma, forming with it a single unit in continuity.
• The trigone, while flattening during bladder filling, can act as a sphincter.

13. Male Urethra • 4 parts : -
• Pre prostatic(Bladder neck),
• Prostatic,
• Membranous(Surrounded by
EUS) and
• Bulbar/penile urethra.
• EUS covers the ventral surface of the
prostate as a crescent shape proximal to
the verumontanum, then assumes a
horseshoe shape distal to the
verumontanum and is crescent in shape
at the bulbar urethra.

14. Female Urethra
• 3-4 cm , short , muscular tube
• Extends throughout the distal third
of the anterior vaginal wall from the
bladder neck to the meatus
• Female EUS covers the ventral
surface of the urethra in a
horseshoe configuration and
promotes continence.

15. Female urethra :-
• Striated sphincter:-
– poorly defined outer
circular layer
– Longitudinal layer
shortens with voiding
• Sub mucosal vasculature:-
– Rich vascular plexus
– Seal effect during filling
• Squamous epithelium: -
– distal urethra- sensitive
to estrogen

16. Urinary continence during elevations in
intraabdominal pressure
• Passive transmission of abdominal pressure to the proximal urethra
• Guarding reflex involving an active contraction of striated muscle of the
EUS can transiently help continence
• Active urethral continence (neural) mechanism in women

17. Hammock hypothesis
– (DeLancey)
• Abdominal pressure transmitted
through the proximal urethra presses
the anterior wall against the posterior
wall.
• Tissue under the urethra provides a
Hammock of support to compress it
and keep it closed when intra
abdominal pressure rises.
• The underlying urethral support
consists of pubocervical
adventitia/fascia and Vagina, which
are attached laterally to the pubic
bone by arcus tendineus fasca pelvis
and levator ani muscle.

19. female Male

20. Mucosa : -
• Common to both sexes
• organised in longitudinal folds that
give the urethral lumen a stellate
appearance when closed. This
arrangement allows considerable
distensibility.
• The surface tension may be a factor
in urethral closure.

21. • Submucosa : - acts in a passive plastic way to “fill in” between the folds of
mucosa as the urethra closes.
• This occurs as the tension increases in the muscular wall of the urethra,
and its effect is to improve the efficiency of the seal of the urethral lumen.

22. Urethral sphincter
Composed of 2 morphologically related but functionally unrelated components : - inner
lissosphincter of smooth muscle and an outer rhabdosphincter of skeletal muscle
• Lissosphincter
• forms a complete cylinder of circular
muscle fibers around the urethra.
• Does not show appreciable change
after puberty.
• Rhabdosphincter
• From the perineal membrane to the
prostatic apex the skeletal muscle fibers
unite behind the urethra in a central
fibrous raphe, while more proximal they
form a cap on the anterolateral side of
the prostate.
• Atrophy of its prostatic part, of which
the fibers become indistinctly dispersed
among the smooth muscles and glands
of the prostate.

24. Physiologic correlate
• Passive Continence by the Lissosphincter :-
– involuntary aspect of micturition
– primarily and exclusively a function of the urethral lissosphincter
– Evidences –
• 1) Urine is normally held at the level of the vesical orifice, which is
a smooth muscle function.

25. • 2) Post-prostatectomy incontinence results from resecting a few mm in
depth distal to the verumontanum, which obviously injures the
lissosphincter but leaves the more distal rhabdosphincter intact.
- Gudziak MR, McGuire EJ and Gormley EA: Urodynamic assessment
of urethral sphincter function in post-prostatectomy incontinence. J Urol
1996

26. • 3) After posterior anastomotic urethroplasty, which includes excision of
the main part of the rhabdosphincter, continence is achieved only by the
bladder neck and supramontanal urethra, where the proximal part of the
lissosphincter is located.
- Koraitim MM, Atta MA, Fattah GA and Ismail HR: Mechanism of
continence after repair of post-traumatic posterior urethral strictures.
Urology 2003.

27. • 4) No effect on passive continence after rhabdosphincter paralysis by
curare injection, as demonstrated by Lapides on himself.
- Lapides J, Sweat R and Lewis L: Role of striated muscle
in micturition. J Urol 1957;

28. Mechanism of Lissosphincter
• Contraction of its circular muscle fibers, resulting in closure of the vesical
orifice and concentric narrowing of the posterior urethra.
• Maximum closure may be assumed to be at the level of the vesical orifice,
where the lissosphincter is most thick, and in the membranous urethra,
where the urethra is most narrow.
• The presence of the whole length of the lissosphincter is not essential to
maintain continence (the proximal or the distal part of the sphincter
alone).

29. • a minimal length of lissosphincter is crucial for this function, below which
incontinence is inevitable.
- Myers RP: Male urethral sphincteric anatomy and radical
prostatectomy. Urol Clin North Am 1991

31. Female continence mechanism
• 1. Smooth and striated muscle cells in and around the urethra close the
urethral lumen (active sphincteric system) - Constantinou and Govan,
1982
• 2. The length of the urethra and urethral wall tension (collagen and elastic
fibers, mucosa and submucosal cushion of blood vessels in the urethral
wall) --passive sphincteric system or urethral wall factor - a third of the
urethral closure pressure.

32. • 3. Pressure transmission from the abdominal cavity to the proximal
urethra (passive pressure transmission) .
• 4. Activation of the coughing reflex via the pudendal nerve leads to a fast
contraction of the urethral rhabdomyosphincter and pelvic floor before
and during vesical pressure increase (active pressure transmission) .

33. • 5. Posterior urethral wall support by fibromuscular tissue of the anterior
vaginal wall and the tendinous arch of the pelvic fascia (hammock system)
- DeLancey.
• 6. Ventral kinking of the urethra during contraction of the levator ani
muscle, longitudinal muscle of the anus, and the hammock muscle pulls
the vagina and bladder base back- and downward and presses the urethra
against the pubic bone (integral theory) -(Oelrich, 1983; DeLancey)

34. Fiber Types of Urethral Striated Muscle
• Slow-twitch fibers - maintaining sphincter tone for prolonged periods
• Fast-twitch fibers - maintain continence when intra-abdominal pressure is
abruptly increased.
• The EUS - two parts.
• The periurethral striated muscle of the pelvic floor contains both fast-
twitch and slow-twitch fibers.
• The striated muscle of the distal sphincter mechanism contains
predominantly slow-twitch fibers (Elbadawi, 1984) and provides more
than 50% of the static resistance (Tanagho et al, 1989).

35. • In the male, the rhabdosphincter consists of 35% fast-twitch and 65%
slow-twitch fibers (Padykula and Gauthier, 1970).
• In the female, the ratio of slow-twitch to fast-twitch fibers is 87% slow-
twitch and 13% fast-twitch fibers.
• It has been speculated that the successful treatment of stress
incontinence by pelvic floor exercises or electrostimulation is caused by
the conversion of fasttwitch to slow-twitch striated muscle fibers.

36. Hormonal control
• Female genital and lower urinary tract share a common embryological
origin, arising from the urogenital sinus, so Both are sensitive to the
effects of female sex steroid hormones.
• Estrogen receptors(ER α, ER β- Elwood Jensen) have been demonstrated
throughout the female lower urinary tract.

37. • α receptors are localized in the urethral sphincter and when sensitized by
estrogens are thought to help maintain muscular tone.
• Estrogens may affect continence by –
– Increasing urethral resistance,
– raising the sensory threshold of the bladder, or
– by increasing α adrenoreceptor sensitivity in the urethral smooth
muscle

38. • Measurement of the urethral pressure profile in nulliparous
premenopausal women shows there is an increase in functional
urethral length midcycle and early in the luteal phase
corresponding to an increase in plasma estradiol.
• Detrusor overactivity in the luteal phase of the menstrual cycle may
be associated with raised plasma progesterone- detrusor
overactivity found in pregnancy
• Van Geelen JM , Doesburg WH , Thomas CMG .Urodynamic
studies in the normal menstrual cycle:The relationship between
hormonal changes during the menstrual cycle and the urethral
pressure profile. Am J Obstet Gynaecol 1981

39. Mechanisms of estrogen on continencce
• Neurological Control- Estrogen receptors have been demonstrated in the
cerebral cortex, limbic system, hippocampus, and cerebellum
• Bladder Function - reduce the amplitude and frequency of spontaneous
rhythmic detrusor contractions and increase the sensory threshold of the
bladder in some women.
• Urethral function - increase the number of periurethral vessels, so
increases urethral closure pressure

40. • Collagen - alteration in systemic collagenase activity and urodynamic
stress incontinence, and urogenital prolapse has been associated with a
reduction in both vaginal and periurethral collagen.

41. Estrogens in the Management
of Incontinence
• overall significant effect of estrogen therapy on subjective
improvement in all subjects an for subjects with urodynamic stress
incontinence alone.
• Oestrogen therapy in the management of incontinence
in postmenopausal women: A meta-analysis. First
report of the Hormones and Urogenital Therapy
Committee . Obste Gynaecol 1994

42. INTERSTITIAL CELLS: THEIR ROLES IN MUSCLE AND
SUBUROTHELIAL LAYERS
• Cells resembling the Interstitial Cells of Cajal (ICC) in the G-I tract.
• Suburothelial interstitial cells :- exhibits rhythmic small transient
contractions during the filling phase
• Interstitial cells in the detrusor layer:- might function as pacemaker or
modulator cells initiating or regulating “non-voiding” activity.

43. Neurogenic control
• Central Control of Micturition
• Reflex Mechanisms Involved in Micturition Control
• Peripheral Control of Micturition

44. Central Control of Micturition
• Schematic representation of possible connections and interactions existing among various brain structures thought to be involved in micturition
control . The exact direction of interactions has yet to be clarified. PAG = Periaqueductal gray

45. • Peri-aquaeductal grey (PAG) and the pontine micturition center (PMC),are
key centers in the supraspinal control of micturition and continence.
• An fMRI study of the role of suprapontine brain structures In the
voluntary voiding control induced by pelvic floor contraction .
Neuroimage 2005 .
• Anterior cingulate gyrus, the prefrontal cortex, and the insula appear to be
involved in the perception of a full versus empty bladder.

46. • Women with urinary retention due to a primary disorder of urethral
sphincter relaxation (Fowler’s syndrome) had activation of cortical regions
without midbrain or brain stem activity.
• Dasgupta R , Critchley HD , Dolan RJ , Fowler CJ
. Changes in brain activity following sacral
neuromodulation for urinary retention . J. Urol
2005
• Increased activation of cortical areas but with a wea activation of the
orbitofrontal cortex was seen in patients with idiopathic detrusor
overactivity (IDO) on filling.
• Griffiths D , Derbyshire S , Stenger A , Resnick N
. Brain control of normal and overactive
bladder . J Urol 2005

47. Reflex Mechanisms Involved in
Micturition Control
• Reflexes promoting urine storage :- sympathetic and somatic (pudendal)
nerves that mediate efferent input to the urethral sphincter and inhibitory
input to the bladder.
• Reflexes promoting micturition :- parasympathetic nerves mediating
efferent input to the detrusor and inhibitory input to the urethral
sphincters.

48. • The “guarding reflex” :- parasympathetic afferent firing from the
bladder during filling activates the external urethra sphincter via a
synapse with sacral interneurons, which results in stimulation of the
pudendal urethral efferents.
• When micturition threshold is reached and voiding is initiated,
urethral sphincter activity ceases first, followed by a rise in detrusor
pressure due to detrusor contraction and flow of urine.
• Micturition is further promoted by a bladder-to-bladder excitatory
reflex and a bladder-to-urethral sphincter inhibitory reflex, which
are activated when the bladder is full.

49. Bladder–sphincter–
bladder reflex pathway
in which the bladder-to-external
urethral sphincter excitatory reflex
activates the urethral sphincter-to-
bladder inhibitory reflex via
interneuronal synapses facilitates
urine storage.

50. Peripheral Nervous System
• Three sets of peripheral nerves :-
• Pelvic parasympathetic - arise at the sacral level of the spinal cord, excite
the bladder, and relax the urethra
• Lumbar sympathetic - inhibit the bladder body and excite the bladder base
and urethra
• somatic nervous systems - Pudendal nerves excite the EUS. These nerves
contain afferent (sensory) as well as efferent axons

51. Peripheral Control of Micturition
• Bladder sensation is conveyed by 2 types of afferent axons :-
• The myelinated Aδ- fibers - sensitive to mechanical stimuli, e.g.,
distension, stretch
• The unmyelinated C- fibers - primarily nociceptive, e.g., chemical
irritation and cooling.
• The efferent parasympathetic input, mediated by acetylcholine (ACh)
receptors in the bladder wall, results in contraction of the detrusor muscle

59. • Neurogenic detrusor overactivity - emergence of an aberrant C-fiber–
driven sacral spinal reflex i.e becoming sensitive to mechanical stimuli
(mechanosensitive).
• Basis for the use of deafferenting neurotoxins, such as capsaicin (CAPS)
and resiniferatoxin (RTX), in the treatment of lower urinary tract
symptoms (LUTS).
• Dasgupta P , Chandiramani VA , Beckett A ,
et al. The effect of intravesical capsaicin on
the suburothelial innervation in patients
with detrusor hyper-reflexia . BJU Int 2000