46

Practical Urology: EssEntial PrinciPlEs and PracticE

wall of the pelvis,and a visceral layer covering the

nomenclature. Particularly the presence of a

pelvic organs. The tendinous arch represents the

deep transverse perineal muscle is under exten-

transition between the parietal and visceral part.

sive discussion, as demonstrated below.

Often the visceral layer is clinically indicated as

The pelvic diaphragm consists of the levator

the endopelvic fascia, especially with regard to

ani muscle and the coccygeus muscle (M. ischio-

radical prostatectomy and nerve-sparing proce-

coccygeus). The levator ani muscle in turn con-

dures. Whether the prostate is actually separated

sists of the following structures, which are

by its own prostatic fascia is under discussion.

named according to their origins and insertions:

The absence of the fascia in the apical region of

the pubococcygeus muscle, iliococcygeus mus-

the prostate and the formation of the so-called

cle and puborectalis muscle. A superior and

puboprostatic ligaments5 by the endopelvic fas-

inferior fascia covers the levator ani muscle, the

cia suggest that the visceral layer of the pelvic fas-

superior layer being part of the parietal layer of

cia (= endopelvic fascia) and the fascia of the

the pelvic fascia as described above. The levator

prostate correlate. The puboprostatic ligaments

ani muscle forms an archway-shaped opening

between the anterior fascia of the prostate and

for the anus and urethra in males, and the anus,

the pubic bone/symphysis pubis do not represent

vagina and urethra in females. The innervations

ligamentous structures in the proper sense. In

for the striated muscles derive principally from

fact the puboprostatic ligaments are character-

the sacral plexus (S3 and S4); some nerve fibers

ized by an aggregation of the pelvic fascia.

reach the puborectal muscle via the pudendal

Possibly muscle fibers (smooth or striated) also

nerve located in the pudendal canal. Even

contribute to the configuration of the so-called

though the contributions of the shape topogra-

puboprostatic ligaments.

phy and the contraction of the pelvic diaphragm

Similarly there is a lack of clarity regarding

to anal continence seem to be proven, it is still

Denonvilliers’ fascia. The anatomical nomencla-

unclear to what extent these anatomical struc-

ture utilizes the description rectoprostatic fascia

tures also affect urinary continence. Recent

or septum. It represents a membranous separa-

publications have reported the muscular inde-

tion between the rectum and the prostate/uri-

pendence between the pelvic diaphragm and

nary bladder.The fascia emerges from two layers

the striated external urethral sphincter, whereas

of a peritoneal cul-de-sac, ranging from the

an association by connective tissue forming a

deepest point of the rectovesical excavation to

tendinous connection starting from the inferior

the pelvic floor. There has been extensive dis-

part of the external urethral sphincter in females

cussion about the possibility of surgical separa-

could be demonstrated. Especially because of

tion of both layers during radical prostatectomy.

these interactions,the authors suggest the neces-

Currently it is evident that microscopically the

sity of an intact pelvic diaphragm for urinary

rectoprostatic fascia consists of two formerly

continence.

peritoneal layers, which often cannot be divided

Considering the urogenital diaphragm, the

bluntly. It is assumed that authors illustrating

exact anatomical and histomorphological com-

techniques of fascia separation are referencing

position is still undefined. Almost all anatomi-

the space between Denonvilliers’ fascia and the

cal atlases report that the urogenital diaphragm

rectal fascia propria (a part of the visceral layer

consists of the deep transverse perineal muscle

of the pelvic fascia = endopelvic fascia).

(less developed in females) with a superior and

Periprostatic neural and vascular structures are

inferior urogenital fascia. Additionally, the

focused on below.2,3,5-10

superficial transverse perineal muscle inserting

at the perineal body (= central tendon of the

perineum),the striated external urethral sphinc-

Pelvic Floor

ter and the surrounding connective tissue com-

plete the traditional view of the urogenital

diaphragm. Some authors report the existence

Two fibromuscular layers are responsible for the

of a deep transverse perineal muscle, but most

closure of the inferior pelvic aperture: the pelvic

recent studies could not verify this conclusion.

diaphragm and the urogenital diaphragm. It has

The urogenital diaphragm is described as layers

to be emphasized at this point that the term uro-

of connective tissue embedding the external

genital diaphragm is not part of the anatomic

urethral sphincter in conjunction with the

48

Practical Urology: EssEntial PrinciPlEs and PracticE

the urinary bladder (and most probably of the

proximal urethra as well) run along the para-

sympathetic nerves. Contraction of the detrusor

muscle is mediated through the parasympa-

thetic nervous system. The pudendal nerve is

part of the somatic nervous system and inner-

vates the striated parts of the external urethral

sphincter. The pudendal nerve courses in the

pudendal canal at the bottom of the inferior

pubic bone after the distribution of the lum-

bosacral plexus. The variation of an intrapelvic

nerve branching off the pudendal nerve prior to

entering the pudendal canal and running on the

inside of the levator muscle has been described.

Stimulation results in increased contraction of

the external urethral sphincter and adjacent

segments of the levator muscle. Complex inter-

connections of the different sections of the cen-

tral nervous system, including Onuf’s nucleus

(located in the sacral part of the spinal cord), the

Figure 3.5. nerve course of the sympathetic fibers deriving

periaqueductal gray, the pontine micturition

center and the frontal lobe of the cerebrum, are

from the superior hypogastric plexus (ci: common iliac artery, u:

involved in the process of filling and emptying.

ureter). (reprinted from schilling et al.18 with permission from

wiley-Blackwell).

For example, it could be demonstrated that pel-

vic floor training for stress urinary incontinence

not only influences the competence of the

medial to the crossing of the distal ureter and

sphincteric mechanisms, but the training also

the common iliac artery on both sides (Fig. 3.5).

results in restructuring of supraspinal central

The plexus is part of the rectouterine or rec-

nervous system components.2,3,18-22

tovesical fold beside the pouch of Douglas

(Fig. 3.3). The plexus extends laterally to the

Prostate, Seminal Vesicles and

rectum, the vagina (in females), the bladder

neck and the seminal vesicles (in males) in a

Deferent Ducts

sagittal direction. The continuing course of

nerve fibers along the prostate is described in

the following chapter. An allocation of nerve

The prostate is often compared to a chestnut of

fibers within the plexus to innervated targets

about 20 g. With the base aligned to the urinary

seems to be possible. Roughly, the anterior part

bladder and the apex proximate to the external

is responsible for urogenital innervations, and

urinary sphincter, the prostate incorporates

the posterior part serves the rectum.

the prostatic urethra with a length of about 3 cm.

The sympathetic fibers of the hypogastric

McNeal defined the different zones of the

plexus originate from the superior hypogastric

prostate based on histopathological analysis: the

plexus, which is fed by nerve fibers from two

peripheral zone, the central zone, the transi-

superior retroperitoneal sympathetic chains

tional zone and the anterior fibromuscular zone.

called the sacral splanchnic nerves. Sympathetic

This definition has to be separated from the

excitation generally results in inhibition of the

macroscopic classification into lobes. The ejacu-

detrusor muscle and stimulation of the smooth

latory ducts are paired tubes formed on each

muscle sphincter cells, which leads to a filling of

side by fusion of the deferent duct and the duct

the urinary bladder. The parasympathetic fibers

of the seminal vesicle. The orifices of the ejacu-

derive from the sacral spinal cord (S2–S5) and

latory ducts are located on the seminal collicu-

reach the inferior hypogastric plexus via pelvic

lus (also called the verumontanum). Fifteen to

splanchnic nerves exiting from the foramina of

thirty orifices of ducts of the prostate glands are

the sacral bone. Sensory afferent nerve fibers of

located beside the seminal colliculus.

The seminal vesicles are located lateral to the

The description of the anatomic affiliations of

deferent ducts. Dorsally and laterally fibers from

pelvic lymph nodes to the drainage field was

the inferior hypogastric plexus engulf the vesi-

originally based on lymphographic studies.

cles. The space between Dennonvillier’s fascia

Recent findings are the results of sentinel lymph

dorsally and the fascia covering the posterior

node studies.The injection of 99mTc-labeled nano-

wall of the bladder is called the spatium urovesi-

colloid into the prostate facilitates the identifica-

cale (urovesical space). Branches of the inferior

tion of sentinel lymph nodes either by surgery or

vesical artery, the middle rectal artery and the

by radiological imaging (Fig. 3.6). The lymph

artery of the vas deferens usually reach the sem-

nodes of the obturator fossa, the external iliac

inal vesicle at its tip.

lymph nodes, the internal and finally the com-

The deferent duct is characterized by a dilata-

mon iliac lymph nodes are responsible for the

tion prior to the confluence with the duct of the

drainage of the prostate gland (Figs. 3.4 and 3.7).

seminal vesicle called the ampulla. The deferent

Although oncological aspects are still the main

duct is accompanied by one or two separate

concern of every radical prostatectomy treating

arteries (arteries of the vas deferens), which

prostate cancer, quality of life aspects including

derive from the inferior vesical artery.

erectile function as well as continence have

The inferior vesical and the middle rectal

become important. The existence of the endopel-

artery contribute to the blood supply of the

vic fascia equipollent to the visceral layer of the

prostate. The main vessels enter the prostate on

pelvic fascia has been outlined above. Most

both sides at the dorsolateral aspect close to the

authors would agree that the neurovascular

base of the prostate. Smaller vessels perforate the

structures are located between the prostate sur-

prostate capsule directly.Venous drainage moves

face with its fibromuscular capsule and the vis-

from the surrounding prostatic venous plexus.

ceral layer of the pelvic fascia, which extends to

Accessory pudendal arteries can be found in

Denonviellers’ fascia at the dorsolateral aspect of

about 25% of the patient population undergoing

the prostate (Fig. 3.8). Some studies describe a

radical prostatectomy. An accessory pudendal

merger between these two layers. Whether ner-

artery is defined as a vessel starting above the

vous tissue can also be found in the fold between

level of the levator ani running down to the penile

the visceral and the parietal layer of the pelvic

structures below the symphysis pubis and the

fascia remains unclear. In 1985, Donker, Walsh

pubic bone, respectively. Some authors subdivide

et al. were the first to extensively describe the

the accessory arteries into lateral (alongside the

neurovascular bundle. The technique of nerve-

anterolateral aspect of the prostate) and apical

sparing radical prostatectomy and cystectomy

(inferior and lateral to the puboprostatic liga-

was adapted regarding these anatomical find-

ments) accessory pudendal arteries.The extent of

ings. Especially the course of these periprostatic

their contribution to the erectile function of the

nerves has resurfaced as a focus of academic

penis is still under investigation and discussion.

interest. The entry of the inferior hypogastric

The puboprostatic complex includes the pubo-

plexus into the pelvis and its location lateral to

prostatic ligaments, the prostatic venous plexus

the seminal vesicles, including the convergent

and their correlation to the prostate and the

fibers of the sacral splanchnic nerves (sympa-

external urethral sphincter. The puboprostatic

thetic) and pelvic splanchnic nerves (parasym-

ligaments formed by the endopelvic fascia, first

pathetic), has been referred to above. In contrast

described by Young, are described above. The

to a separate dorsolateral nerve bundle, several

prostatic venous plexus communicates exten-

authorsreinvestigatedtheanatomyanddescribed

sively with the distinct venous plexus of the uri-

different nerve dispersions. The periprostatic

nary bladder cranially and the superficial/deep

nerves proceed divergently especially in the mid-

dorsal veins of the penis. The proper name

part of the prostate; therefore, a varying amount

(Santorini’s plexus) refers to their initial discov-

of nerve tissue can be found also in the anterior

ery by Giovanni Domenico Santorini in 1724. The

and anterolateral aspect of the prostate in addi-

venous plexus is imbedded in the fibrous struc-

tion to the known accumulation in the dorsolat-

ture of the so-called puboprostatic ligaments.The

eral course (Fig. 3.9). Characteristically, nerve

puboprostatic plexus directly covers the anterior

fibers converge towards the apex located at the

elevated part of the external urethral sphincter

posterior and posterolateral side of the apex and

(see also Chap. Sphincter Mechanisms).

the urethra, respectively. In addition, parts of the