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EUROPEAN UROLOGY 70 (2016) 301–311
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Collaborative Review – Prostate Cancer
A Critical Analysis of the Current Knowledge of Surgical Anatomy
of the Prostate Related to Optimisation of Cancer Control and
Preservation of Continence and Erection in Candidates for Radical
Prostatectomy: An Update
Jochen Walz a,*, Jonathan I. Epstein b, Roman Ganzer c, Markus Graefen d, Giorgio Guazzoni e,
Jihad Kaouk f, Mani Menon g, Alexandre Mottrie h, Robert P. Myers i, Vipul Patel j,
Ashutosh Tewari k, Arnauld Villers l, Walter Artibani m
a
Department of Urology, Institut Paoli-Calmettes Cancer Centre, Marseille, France;
c
b
Departments of Pathology, Urology, and Oncology, Johns Hopkins
d
Medical, Baltimore, MD, USA; University of Leipzig, Leipzig, Germany; Martini Clinic, Prostate Cancer Centre, Hamburg, Germany; e Department of Urology,
Humanitas Research Hospital, Rozzano, Italy; f Glickman Urological and Kidney Institute, Cleveland Clinic, Cleveland, OH, USA; g Vattikuti Urology Institute,
Henry Ford Health System, Detroit, MI, USA; h Onze Lieve Vrouw Robotic Surgery Institute, Aalst, Belgium; i Institute of Urology, Lahey Hospital and Medical
Center, Burlington, MA, USA; j Global Robotics Institute, Florida Hospital Celebration Health, Celebration, FL, USA; k Prostate Cancer Institute, Department of
Urology, Weill Cornell Medical College, New York, NY, USA; l Department of Urology, Centre Hospitalier Régional Universitaire de Lille, Lille, France;
m
Department Urology, University of Verona, Verona, Italy
Article info
Abstract
Article history:
Accepted January 18, 2016
Context: In 2010, we published a review summarising the available literature on
surgical anatomy of the prostate and adjacent structures involved in cancer control
and the functional outcome of prostatectomy.
Objective: To provide an update based on new literature to help the surgeon improve
oncologic and surgical outcomes of radical prostatectomy (RP).
Evidence acquisition: We searched the PubMed database using the keywords radical
prostatectomy, anatomy, neurovascular bundle, nerve, fascia, pelvis, sphincter, urethra,
urinary continence, and erectile function. Relevant articles and textbook chapters
published since the last review were critically reviewed, analysed, and summarised.
Moreover, we integrated aspects that were not addressed in the last review into this
update.
Evidence synthesis: We found new evidence for several topics. Up to 40% of the crosssectional surface area of the urethral sphincter tissue is laterally overlapped by the
dorsal vascular complex and might be injured during en bloc ligation. Denonvilliers
fascia is fused with the base of the prostate in a horizontal fashion dorsally/caudally of
the seminal vesicles, requiring sharp detachment when preserved. During extended
pelvic lymph node dissection, the erectile nerves are at risk in the presacral and internal
iliac area. Dissection planes for nerve sparing can be graded according to the amount of
tissue left on the prostate as a safety margin against positive surgical margins. Vascular
structures can serve as landmarks. The urethral sphincter and its length after RP are
influenced by the shape of the apex. Taking this shape into account allows preservation
of additional sphincter length with improved postoperative continence.
Conclusions: This update provides additional, detailed information about the surgical
anatomy of the prostate and adjacent tissues involved in RP. This anatomy remains
Associate Editor:
Stephen Boorjian
Keywords:
Prostate
Prostate cancer
Anatomy
Neurovascular bundle
Sphincter
Radical prostatectomy
Erectile dysfunction
Urinary continence
Urethra
* Corresponding author. Department of Urology, Institut Paoli-Calmettes Cancer Centre, 232, Bd Ste.
Marguerite, 13009 Marseille, France. Tel. +33 491223532; Fax: +33 491223613.
E-mail address: [email protected] (J. Walz).
http://dx.doi.org/10.1016/j.eururo.2016.01.026
0302-2838/# 2016 European Association of Urology. Published by Elsevier B.V. All rights reserved.
302
EUROPEAN UROLOGY 70 (2016) 301–311
complex and widely variable. These details facilitate surgical orientation and dissection
during RP and ideally should translate into improved outcomes.
Patient summary: Based on recent anatomic findings regarding the prostate and its
surrounding tissue, the urologist can individualise the dissection during RP according to
cancer and patient characteristics to improve oncologic and functional results at the same
time.
# 2016 European Association of Urology. Published by Elsevier B.V. All rights reserved.
1.
Introduction
In 2010, we published a review on the current knowledge of
the anatomy of the prostate and surrounding tissue with the
aim of helping urologists better understanding the diverse
structures encountered during radical prostatectomy (RP)
and applying the current nomenclature for these structures
correctly [1]. We now present an update, taking the most
recent research results into consideration as well as the
most recently published technical variations of RP and
adding topics that we left out of the previous article.
2.
Evidence acquisition
We searched the PubMed database to identify original and
review articles in English that addressed the anatomy of the
prostate and relevant structures adjacent to the prostate,
with an emphasis on work published after the publication of
our previous review (February 2010 to July 2015). The
keywords used were prostate, radical prostatectomy, anatomy, neurovascular bundle, nerve, fascia, pelvis, sphincter,
urethra, urinary continence, and erectile function. Relevant
articles and textbook chapters were reviewed, analysed,
[(Fig._1)TD$IG]and summarised, with the consensus of all authors.
3.
Evidence synthesis
Regarding the pubovesical/puboprostatic ligaments, the
accessory pudendal arteries, the vesicoprostatic muscle,
and the periprostatic fascia, no new anatomic knowledge
was acquired (Figs. 1–4). Consequently, we refer to the
previous article for this information [1].
3.1.
Dorsal vascular complex
The dorsal vascular complex (DVC) overlies the urethral
sphincter ventrally. During its ligation, injury to the
sphincter tissue is possible, resulting in potentially decreased postoperative continence. A recent study by Ganzer
et al demonstrated that 37% and 30% of the cross-sectional
urethral sphincter surface area are laterally overlapped by
the DVC at the prostate apex and 5 mm distal to the apex,
respectively. The DVC covers the urethral sphincter tissue
laterally and dorsally (Fig. 3) [2]. In the case of transverse en
bloc ligation of the DVC dorsal to its lateral limits, a
substantial portion of the sphincter tissue might be
included in the ligation and rendered nonfunctional. To
avoid this problem, selective dissection and ligation of the
DVC is strongly recommended [2,3].
Fig. 1 – Axial section of prostatic and periprostatic fascia at midprostate.
A = apex; AFMS = anterior fibromuscular stroma; B = bladder; DA = detrusor apron; DF = Denonvilliers fascia; DVC = dorsal vascular complex;
FTAP = fascial tendinous arch of pelvis; LAF = levator ani fascia; M = midprostate; NVB = neurovascular bundle; PC = pseudocapsule; PPF = periprostatic
fascia; PPF/SVF = posterior prostatic fascia/seminal vesical fascia; PRS = perirectal space; PZ = peripheral zone; R = rectum; SV = seminal vesicle;
TZ = transition zone; U = urethra; VEF = visceral endopelvic fascia.
EUROPEAN UROLOGY 70 (2016) 301–311
[(Fig._2)TD$IG]
303
Fig. 2 – Midline sagittal section of prostate, bladder, urethra, and striated sphincter.
B = bladder; CS = colliculus seminalis (verumontanum); DA = detrusor apron; DF = Denonvilliers fascia; DVC = dorsal vascular complex; MDR = medial
dorsal raphe; PC = pseudocapsule of prostate; PPF/SVF = posterior prostate fascia/seminal vesicle fascia; PS = pubic symphysis; R = rectum;
RU = rectourethralis muscle; SMS = smooth muscle sphincter; SS = striated sphincter; SV = seminal vesicles; U = urethra; VEF = visceral endopelvic fascia;
VS = vesical sphincter; VVPM = vesicoprostatic muscle.
3.2.
Prostate arterial supply
The internal pudendal artery is the prolongation of the
internal iliac artery after branching off the obturator artery,
[(Fig._3)TD$IG]the vesical arteries, and the superior and inferior gluteal
Fig. 3 – Axial section of the sphincteric urethra.
A
]FDI$_T[5 = apex; B = bladder; C SMS = circular smooth muscle sphincter;
DVC = dorsal vascular complex; EPF = endoplevic fascia; LA = levator ani
muscle; LAF = levator ani fascia; L SMS = longitudinal smooth muscle
sphincter; M = midprostate; MDR = median dorsal raphe;
NVB = neurovascular bundle; PB = pubic bone; PV/PPL = pubovesical/
puboprostatic ligament; R = rectum; SS = striated sphincter; SV = seminal
vesicle; U = urethra.
arteries. The most frequent origin of prostate arteries is from
the internal pudendal artery (35–56%) [4,5]. The common
gluteal–pudendal trunk is the next most frequent origin (15–
28%), and less frequently the prostate arteries branch off the
obturator artery (10–12%) or the inferior gluteal artery. Per
side, there is only one common trunk in most cases (60–76%),
and there are anastomoses with the termination of the
internal pudendal arteries (24%), contralateral prostate
arteries (12%), and superior vesical arteries (8%) [4,5]. After
branching off, the artery has a tortuous course obliquely
downward in trajectory towards the posterior and inferior
part of the bladder and provides several inferior vesical
arteries. It terminates with numerous prostate branches,
often after a bifurcation, resulting in two main pedicles. The
urologist can differentiate a posterior pedicle surrounding
seminal vesicles and deferential ducts reaching the prostate
base as well as an anterior pedicle surrounding the lateral
border of the prostate finally running to the prostate apex as
an anterior capsular prostate branch. These latter arteries,
when preserved during RP, may relate to postoperative
erectile function and penile integrity because they may be
responsible for ancillary penile blood flow [6,7]. After
reaching the prostate pseudocapsule, the prostate arteries
give rise to numerous perforating branches to the prostate,
with most penetrations found at the 2 o’clock or 10 o’clock
position for the anterolateral pedicle and at the 5 o’clock or
7 o’clock position for the posterolateral pedicle [4]. The
anterolateral pedicle vascularises mainly the central gland
and the transition zone, whereas the posterior pedicle
vascularises most of the peripheral zone and apical area.
Note that there is considerable inter- and intraindividual
variability in the vascular anatomy.
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EUROPEAN UROLOGY 70 (2016) 301–311
[(Fig._4)TD$IG]
3.4.
Posterior prostatic fascia and seminal vesicles fascia
(Denonvilliers fascia)
Fig. 4 – Coronal section of the prostate, sphincteric urethra, periprostatic
fascia, and associated musculature.
CS = colliculus seminalis (verumontanum); CZ = central zone;
ED = ejaculatory duct; LA = levator ani muscle; LAF = levator ani fascia;
NVB = neurovascular bundle; OI = obturator internus muscle;
PC = pseudocapsule of prostate; PF = prostate fascia; PPF = periprostatic
fascia; PZ = peripheral zone; SMS = smooth muscle sphincter;
SS = striated sphincter; SV = seminal vesicle; U = urethra; VD = vas
deferens.
3.3.
Exterior stromal edge of the prostate versus ‘‘prostate
pseudocapsule’’
There is an ongoing controversy regarding the outer limits
of the prostate. The structure often termed the capsule is the
exterior stromal edge of the prostate parenchyma, formed
by transversely arranged fibromuscular layers of condensed
smooth muscle, with a variable number of glands recognised at the outermost prostate surface [8]. Note that this
condensed fibromuscular layer may intermingle with the
periprostatic tissue, rendering its appearance quite variable
[1]. From a microscopic and pathologic point of view, the
correct term for this layer would be condensed smooth
muscle or the outer edge of the prostate. Despite this
microscopic evidence, from a macroscopic and surgical
point of view, the defined and distinct outer edge of the
prostate, analogous to a capsule, is visibly and grossly
apparent during RP in many cases and is used as a landmark
for proper dissection [9]. Consequently, the coauthors
agreed that the term pseudocapsule might represent an
acceptable compromise to respect its pathologic nature
versus the clinical appearance of the prostate outer limits in
daily practice. Note that the International Anatomical
Terminology refers to capsule (pseudocapsule) [10].
A recent work from Muraoka et al investigated the intraand interindividual variations of the posterior prostatic
fascia (PPF) and seminal vesical fascia (SVF) (Figs. 1 and 2).
They showed that although its configuration appeared to be
a firm membranous structure, it was actually recognised as
a fascicle of multiple leaves with interlacing branches, with
multiple leaves mainly ventrally, and a disorderly, loose
connective tissue mainly dorsally [11]. They observed a
fusion between the PPF/SVF and the pseudocapsule near the
base of the prostate at the insertion of the seminal vesicles
(Fig. 2). The PPF/SVF extended and dispersed laterally into
the neurovascular bundle (NVB), and periprostatic nerves
ran between multiple leaves and appeared embedded in the
fascial complex between PPF/SVF leaves and the pseudocapsule.[11] Another recent work by Kim et al suggests that
the tissue quality of PPF/SVF varies among patients as its
origin might be induced by tissue tension, created by organ
development in the pelvis and not by tissue fusion as
suggested previously. As this development can vary
substantially from patient to patient, the fascia can have
a multilayer configuration, a fragmentation into short
pieces, or be composed of a thick leaf [12]. This theory
supports the observations from Muraoka et al as well as
clinical experience, in which tissue quality varies [13].
3.5.
Neurovascular bundle
3.5.1.
Neurovascular bundle and pelvic lymph node dissection
In the male, the inferior hypogastric plexus, or pelvic plexus,
is responsible for the mechanisms of erection, ejaculation,
and urinary continence [14]. The pelvic plexus lies within a
fibrofatty, flat, rectangular, sagittally oriented plate between the bladder and the rectum [14–17]. Pelvic lymph
node dissection (PLND) might be extended into this area.
Currently, a standard PLND is defined as a dissection of the
fibrofatty tissue between the landmarks of the external iliac
artery and the pelvic musculature laterally, the inner
femoral canal distally, the common iliac artery or the
bifurcation with the ureter proximally, and the bladder wall
medially, including a dissection around the internal iliac
artery [18,19]. In a recent lymph node mapping study, such
a dissection field allows the urologist to correctly stage
patients as N0 or N1 in 94% of all cases and removes 87% of
all positive nodes [20]. In the same study, a more limited
dissection field (external iliac vessels and obturator fossa)
correctly staged only 76% of all patients and removed only
52% of all positive nodes [20]. An extended PLND (ePLND)
might extend the dissection up to the common iliac arteries
as well as to the presacral areas [18,19]. Such a dissection
would correctly stage 97% of all patients, and 99% of all
positive nodes would be removed [20]. The pelvic plexus
and the erectile nerves are at risk in standard dissection
during the medial dissection in the area of the internal iliac
artery and towards the bladder wall. During ePLND, the
nerves are also at risk at their origin in the presacral area
and medial to the common iliac vessels. In fact, decreased
EUROPEAN UROLOGY 70 (2016) 301–311
erectile function in patients with a more extended yield
of lymph nodes relative to patients with a lower yield or
no lymph node dissection has been demonstrated
[21,22]. Others could not find any influence from the extent
of PLND on erectile function [23]. Nevertheless, from an
anatomic point of view, ePLND occurs near or inside the
pelvic plexus and thus can lead to injury of proerectile nerves.
This should be considered when performing PLND during
pelvic surgery.
3.5.2.
is questionable [29]. Nevertheless, several studies proved
that the high anterior release concept with preservation of
the anterior nerve fibres improves both erectile function
and urinary continence relative to patients who did not
undergo a high anterior release [36–38]. It remains unclear
whether this effect is a result of the nerve fibres that are
preserved at the anterolateral aspect of the prostate or
whether it is a result of other aspects, such as less traumatic
handling of the NVB; better identification of dissection
planes; or other, hidden technical details [39].
Anterolateral nerves of the neurovascular bundle
Fibres of the pelvic plexus destined for erectile and urinary
function surround the lateral aspect of the bladder neck, the
proximal prostate, and the seminal vesicles [15,16,24]. During their course lateral to the prostate, several studies
confirmed a spraylike distribution of the nerves on the
lateral and anterolateral surface of the prostate up to the
2 o’clock and 10 o’clock positions [24–30]. Ganzer et al,
using computerised planimetry, identified the largest
percentage of periprostatic nerve surface in the posterolateral position. The periprostatic nerve distribution was
variable, with up to 19% of the overall nerve surface in the
anterolateral position [30]. This finding was corroborated
by Alsaid et al, who found that at the midpart the NVBs
became more dispersed, with less than two-thirds of the
periprostatic nerve fibres remaining in the posterolateral
regions and one-third in the anterior and anterolateral
regions. At the apex, 60% of the nerves were located
posterolaterally, and 40% were located anterolaterally
[31]. Clarebrough et al reproduced the methodology of
Ganzer et al and showed that the overall proportion of nerve
surface on whole-mount sections increased at the anterolateral side of the prostate, from 6.0% at the base to 7.6% at
the midpart to 11.2% at the apex, suggesting that especially
at the apex nerve fibres are more predominant along the
anterolateral aspect of the prostate [32]. All these differing
results can be explained by the interindividual variability of
the anatomy as well as by the difference in methodology
(nerve surface vs number of nerve fibres).
3.5.3.
305
Function of nerves lateral to the prostate
The role and function of the anterolateral nerves on the
prostate are controversial, despite several studies that
included immunohistochemical staining of these nerve
fibres. Alsaid et al showed in a foetus aged 17 wk using
three-dimensional (3-D) reconstruction that sympathetic,
parasympathetic, and sensory nerve fibres are found on the
anterolateral aspect of the prostate. Unfortunately, they did
not provide nerve counts [33]. Ganzer et al showed that up
to 14.6% of all parasympathetic nerve fibres are found
anterolaterally, but in their study at the apex, only 1.5% of
all parasympathetic nerves were found anteriorly [34]. A
similar study by Costello et al demonstrated that only 7% of
all parasympathetic nerve fibres are found on the anterolateral aspect of the prostate [35]. As erectile function is
assured by parasympathetic fibres, the physiologic nature
of these fibres makes participation in erectile function
possible, but because of the low percentage of anterolateral
parasympathetic fibres, their influence on overall function
3.5.4.
Compartmentalisation of the neurovascular bundle
Costello et al divided the NVB into the anterior fibres mainly
innervating the levator ani and the prostate and the more
posteromedial located fibres mainly innervating the corpora cavernosa [16]. Tewari et al proposed a longitudinal
trizonal compartmentalisation of the NVB by dividing it into
the proximal neurovascular plate, which is synonymous
with the already-discussed pelvic plexus; the predominant
NVB; and the accessory neural pathways [40]. Accessory
neural pathways were noted within the layers of the
periprostatic fascia up to the anterolateral aspect of the
prostate. Two sets of neural tissue were identified: one
superficial that lays inside of the periprostatic fascia and a
deeper group of nerves travelling within the pseudocapsule
and probably responsible for direct innervation of the
prostate [40]. In fact, a recent study by Ganzer et al
demonstrated that the total nerve surface decreases by 75%
from the level of the seminal vesicles to the urethra, from
50.2 mm2 to 13.3 mm2, suggesting a role for these nerves
other than innervation of the corpora cavernosa [41]. Another study by Alsaid et al based on 3D reconstruction
demonstrated that at the prostate apex and the urethra, the
NVB is separated into two distinct groups: the cavernous
nerves and corpus spongiosum nerves [31]. They demonstrated that the cavernous nerve fibres running to the
corpora cavernosa were a continuation mainly of the fibres
running on the anterior and lateral aspect of the prostate.
The corpus spongiosum nerve fibres running to the corpus
spongiosum were found to be a continuation of the fibres
running at the posterolateral aspect of the prostate
[42]. They concluded that the ideal dissection plane during
nerve sparing should include the preservation of the
anterolateral tissue and fascia to avoid cavernous nerve
lesions [31].
It is noteworthy that despite extensive research in the
field of prostate anatomy, the exact anatomy of the fascia
and the detailed function of the nerve fibres surrounding
the prostate remain controversial and at times contradictory.
3.6.
Anatomic landmarks for nerve sparing and grading of
nerve sparing extent
In daily practice, the substantial interindividual and
intraindividual variations do not allow the urologist to
reproduce the same surgical dissection in every patient, but
the multilayered character of the periprostatic fascia allows
choice in the dissection between nerves and prostate
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EUROPEAN UROLOGY 70 (2016) 301–311
pseudocapsule with the aim of leaving a more or less thick
tissue layer on the prostate as a safety margin. In cases with
a low risk of extraprostatic extension (EPE), a closer
dissection and in cases with a higher risk of EPE a wider
dissection plane can be chosen. This approach was termed
incremental nerve sparing [43,44]. It is known that EPE is in
most cases only a matter of millimetres, which could allow a
nerve-sparing procedure in selected cases with focal EPE
[45]. Inoue et al evaluated the distance between cancer and
the NVB at the classical 5 o’clock and 7 o’clock position in
prostates without nerve sparing. In patients without EPE,
they found a mean distance of 3.3 mm (standard deviation
[SD]: 2.6), 3.4 mm (SD: 2.7), and 3.7 mm (SD: 2.4) at the
apex, midgland, and base, respectively. In patients with EPE,
the distance between cancer and the NVB was 2.0 mm (SD:
1.9), 1.9 mm (SD: 1.9), and 1.8 mm (SD: 2.1) at the apex,
midgland, and base, respectively [46]. Note that in an
individual case, the nerves could be in direct contact with
the NVB. This observation corroborates the possibility of
nerve-sparing procedures despite the presence of EPE in
well-selected patients.
Depending on the dissection plane chosen during the
procedure, several technical variations are possible. Previously, we described intrafascial, interfascial, and extrafascial dissection (Fig. 5a and 5b; Table 1) [1]. Intrafascial
dissection is considered a dissection that follows a plane on
the pseudocapsule, remaining internal to the prostatic
fascia at the antero- and posterolateral aspect of the
prostate and anterior to the PPF/SVF. The intrafascial
approach allows a whole-thickness preservation of the
NVB. Interfascial dissection of the NVB is considered a
dissection within the thickness or between the leaves of the
periprostatic fascia and includes incremental nerve sparing.
Depending on anatomic variations, the NVB might be prone
to partial resection. This approach allows a greater safety
margin around the prostate relative to the intrafascial
dissection, presumably resulting in an oncologically safer
approach [47,48]. The extrafascial dissection is a dissection
[(Fig._5)TD$IG]
Fig. 5 – (a) Overview of an axial section of the prostatic and periprostatic fascia at midprostate (prostate rotated counterclockwise). (b) Enlarged axial
section with three dissection planes: intrafascial, interfascial, and extrafascial. (c) Enlarged axial section with three dissection planes according to the
Pasadena consensus [44]: full, partial, and minimal nerve sparing. (d) Enlarged axial section with four dissection planes according to Tewari et al [40]:
1 = dissection below veins, 2 = dissection on the veins, 3 = dissection distant from the veins, and 4 = extrafascial dissection. (e) Enlarged axial section
with five dissection planes according to Schatloff et al [50]: 1 = extrafascial dissection, 2 = sharp dissection distant from arteries, 3 = sharp dissection on
arteries, 4 = sharp dissection at the level of arteries, and 5 = blunt dissection below arteries.
LA = levator ani muscle; LAF = levator ani fascia; PC = pseudocapsule of prostate; PPF = periprostatic fascia; R = rectum.
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EUROPEAN UROLOGY 70 (2016) 301–311
Table 1 – Overview of the different dissection planes for nerve sparing during radical prostatectomy and their influence on safety margin
and nerve-sparing quality
Author
Dissection plane
Safety margin to avoid PSM
Low
High
[TD$INLE]
Nerve-sparing quality
Good
Previous article Walz et al [1]
Pasadena consensus,
Montorsi et al [44]
Tewari et al [40]
Schatloff et al [50]
Intrafascial
Full nerve sparing
Grade 1
Grade 5
Poor
[TD$INLE]
Interfascial
Partial
nerve sparing
Grade 2
Grade 4
Grade 3
Minimal nerve sparing
Grade 3
Grade 2
Extrafascial
NA
Grade 4
Grade 1
NA = not applicable; PSM = positive surgical margin.
carried out lateral to the levator ani fascia and posterior to
the PPF/SVF. In this case, the NVB will be completely
resected. This approach results in the largest amount of
tissue surrounding the prostate and thus is the most
oncologically safe dissection, but it carries with it probable
complete erectile dysfunction if done bilaterally [47]. Alternate terminology for dissection planes has been suggested
by a consensus panel using the terms full, partial, and
minimal nerve sparing for the intrafascial, interfascial, and
‘‘sub’’ extrafascial dissection, respectively (Fig. 5c; Table 1)
[44]. Note that the estimation of nerve-sparing extent is
subjective, especially in the category of interfascial or
partial nerve sparing.
Recent studies pushed this concept even further and
suggested subdividing the interfascial dissection into near
and far interfascial dissection planes relative to the
pseudocapsule, proposing grading systems to define the
extent of tissue margin on the prostate [6,43].
Tewari et al proposed a grading system based on four
grades of dissection [43]. They used the veins on the lateral
aspect of the prostate as vascular landmarks for the
definition of the dissection planes as well as a scaling
system, with 1 being maximal nerve sparing and 4 being no
nerve sparing (Fig. 5d; Table 1). A dissection between the
periprostatic veins and the pseudocapsule of the prostate is
considered a grade 1 dissection. Cases in which the
dissection is performed just on the veins are considered
grade 2 dissection. When leaving more tissue on the veins
and the prostate, it is considered a grade 3 dissection, and an
extrafascial dissection is a grade 4 dissection [43]. Using the
Tewari system, Srivastava et al demonstrated that the early
return of continence was associated with the grade of nerve
sparing, in which 72% of patients with grade 1 nerve sparing
had early continence versus 55%, 46%, and 44% for grades 2,
3, and 4, respectively [49]. Data on erectile function were
not available.
Patel and coworkers proposed an inverse five-grade scale
of dissection, in which grade 5 represents optimal nerve
sparing and grade 1 no nerve sparing (Fig. 5e; Table 1)
[50]. They used the arterial periprostatic vasculature as a
landmark, with a ‘‘landmark artery’’ running on the lateral
border of the prostate as either a prostate or capsular artery.
Those arteries were identified in 73% of all prostate halflobes [6]. Maximum nerve sparing was termed a grade
5 dissection, and the dissection is performed without the
need for sharp dissection between this artery and the
pseudocapsule outside the prostatic fascia. A grade
4 dissection is performed using sharp dissection in a plane
between the artery and the prostatic pseudocapsule across
the NVB. Intraoperatively, the dissection is confirmed by the
presence of a strip of adipose tissue over the prostate and an
absence of arterial vessels. For a grade 3 dissection, the
plane of nerve sparing is created at the artery’s lateral
aspect; therefore, the artery is clipped at the level of the
prostate pedicle. Intraoperatively, the dissection is identified by the presence of a strip of adipose tissue over the
prostate, with the artery on top. For a grade 2 dissection,
nerve sparing is performed several millimetres lateral to the
artery, following the prostatic contour. Intraoperatively, the
dissection is identified by the presence of a thick fat strip
over the prostate, with arteries embedded. Finally, for a
grade 1 dissection, an extrafascial dissection is performed
[50]. Using this grading system, Schatloff et al reported on
the amount of nerve tissue on the prostate according to the
degree of nerve sparing. They could confirm that with
increasing degrees of nerve sparing, the amount of nerve
tissue on the prostate decreased [50]. Further studies
evaluating the impact of different grades of nerve sparing on
functional outcomes are awaited.
Bearing in mind that the anatomy of the nerves may vary
substantially, the concept of different dissection planes
aims more for an incremental security margin on the
prostate to avoid positive surgical margins (PSMs) than for
true incremental nerves sparing. Incremental nerve sparing
would imply that the course and location of erectile nerve
fibres can reliably be identified, which is not the case
because of their microscopic nature and the varying
anatomy. The degree of nerve sparing with this approach
is uncertain, and the true extent of nerve fibre preservation
in an individual patient cannot reliably be controlled or
predicted. In contrast, the amount of tissue remaining on
the prostate to avoid a PSM can be well controlled during
the procedure, with the aim of achieving an incremental
safety margin to cover the pseudocapsule and cancer, if
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EUROPEAN UROLOGY 70 (2016) 301–311
present. For this reason, the term incremental safety margin
instead of incremental nerve sparing may better reflect this
technical variation [39].
So far, there is no consensus on which grading system
should be used, and a standard system would need clear and
reproducible landmarks to provide comparability and
reproducibility [44]. Moreover, selection of patients for
such an incremental safety margin approach depends on
patient and cancer characteristics and is the fundamental
concern with this technique. Address this issue is beyond
the scope of this review but needs to be taken into
consideration when these variations in surgical techniques
are applied in daily practice.
3.7.
this paper as the urethral sphincter (musculus sphincter
urethrae) [55]. This terminology seems more appropriate as
most of the vesical sphincter tissue is found at the level of the
(caudal) urinary bladder, and its function is to close the
storage organ bladder at the bladder level and not at the
urethral level. Moreover, the vesical sphincter helps separate
the storage organ bladder form the genital part of the
genitourinary tract that then serves for its genital function
(ejaculation). At the same time, the urethral sphincter has its
function at the level of the urethra as it closes the urethra at a
distance to the bladder when activated [55]. Consequently,
the terms vesical sphincter and urethral sphincter will be used
in the following text to replace the terms internal and external
urethral sphincter, respectively.
Pelvic floor musculature
3.8.1.
The innermost muscle of the anterior pelvis is the levator ani
muscle. Close to the urethral sphincter, it has been termed the
puboperinealis muscle and represents the anteromedial
component of the levator ani [3,51,52]. Voluntary contraction of the puboperinealis muscle pulls the urethra and
prostate forward and upward, resulting in closure of the
urethra [51,53]. Innervating this muscle are fibres of the long
pelvic nerve, or levator ani nerve, which runs on the levator
ani surface just lateral to the fascial tendinous arch (Fig. 6)
[54]. For full functional integrity of the puboperinealis and
the quick-stop mechanism, this nerve needs to be identified
and preserved. It might be injured by incision of the
endopelvic fascia and by mobilisation of the levator ani
laterally away from the prostate [54].
3.8.
Bladder neck and urinary sphincter
There are two well-recognised urinary sphincter systems: (1)
a proximal internal urethral sphincter, referred to in this
paper as the vesical sphincter (musculus sphincter vesicae),
and (2) the distal external urethral sphincter, referred to in
[(Fig._6)TD$IG]
Fig. 6 – Intraoperative picture of the long pelvic nerve or the levator ani
nerve (arrow) on the left side of the prostate. Picture taken at the
moment of the endopelvic fascia opening (pelvic wall on the left side,
prostate on the right side). Reproduced with permission from V. Patel,
Ohio State University (Columbus, OH, USA).
Bladder neck and vesical sphincter
The bladder neck is the anatomic area of the urinary bladder
outlet and the entrance to the prostatic urethra. It is formed
by several structures, including detrusor muscle, the vesical
sphincter, and adjacent proximal prostatic tissue. The
detrusor muscle consists of a densely interwoven network
of three recognised smooth muscle layers: an inner
longitudinal layer, a middle circular layer, and an outer
longitudinal layer [55,56]. The detrusor is anteriorly and
laterally in close contact with the bladder neck, but there is
no participation of any of the three layers in the formation of
the vesical sphincter. Some anterior fibres of the outer
longitudinal muscle layer reach out over the prostate to
reach the os pubis in puboprostatic/pubovesical ligaments.
This sheath of smooth muscle is also termed the anterior
detrusor apron (Fig. 2) [1,57]. Posterior fibres of the outer
longitudinal muscle layer cover the trigone posteriorly and
reach out over the bladder neck to penetrate the posterior
aspect of the prostate. This structure is also termed the
vesicoprostatic muscle or posterior detrusor apron (Fig. 2)
[1,58,59]. These muscle bundles attach the urinary bladder
in the pelvis but do not participate in the sphincter system.
The trigone is a creaseless, triangular area extending
anteriorly from the two ureteral orifices to the urethral
opening, with superficial submucosal longitudinal smooth
muscle fibres [55]. This smooth muscle extension is the site
of formation of middle-lobe benign prostatic hyperplasia
(BPH). At its cranial border, the trigone consists of a
transverse, submucosal band formed by the prolongation of
ureteral muscle, extending from one ureteral orifice to the
contralateral orifice [55]. The main part of the trigone is
formed by fibres of the vesical sphincter, which is an elliptic
structure formed by circular smooth muscle fibres surrounding the urethral opening circumferentially. The
urethral opening is eccentrically positioned and located
in the anterior third of the ellipsis. Posteriorly, the circular
muscle fibres reach almost to the ureteral orifices (Fig. 2)
[55]. This muscular structure is part of the vesical sphincter
that assures continuous urinary continence as well as
bladder neck closure during ejaculation to avoid retrograde
ejaculation. Inferiorly, circular fibres of this muscle
surround the proximal prostatic urethra down to the
colliculus seminalis. This part of the sphincter is modified
by and interspersed with the development of BPH, and the
309
EUROPEAN UROLOGY 70 (2016) 301–311
intravesical part may be displaced upward, in this case into
the bladder lumen. The so-called bladder neck–sparing
technique is performed in this anatomic area to improve
postoperative continence. To date, there is a controversy
regarding the effect of bladder neck sparing on urinary
continence, and no clear conclusion for or against bladder
neck sparing can be drawn [44,60–62].
results at the same time. Today, RP is no longer an all-in-one
procedure but rather an individualised operation that
should take many details into consideration.
3.8.2.
Study concept and design: Walz, Artibani.
Urethral sphincter
The urethral sphincter complex is found primarily distal to the
prostate apex. It is in close relationship with but independent
from the levator ani muscle (pars puboperinealis) and thus
independent of the pelvic floor musculature [47,63,64].
The urethral sphincter itself consists of two muscle types
(Fig. 2 and 3). First, the outer striated muscle fibres, described
to be omega shaped and extending to the apex and the
anterior surface of the prostate [65–68]. Recently, an
extension of the striated muscle not only on the outside of
the apex but also inside the apex was suggested [69]. Second,
an inner muscle layer of the urethral sphincter surrounds the
urethra completely and consists of smooth muscle fibres
(outer circumferential and an inner, longitudinally oriented
layer) and elastic tissue [64]. The smooth muscle layer has its
proximal limits at the level of the colliculus seminalis or
verumontanum (Fig. 2) [30,65]. The shape of the prostate at
the apex may vary substantially, directly influencing the
form and length of the urethral sphincter after emerging from
the apex because parts of the urethral sphincter can be found
inside the prostate apex as a distinct structure surrounded by
prostatic tissue [47,69]. The apex may overlap the urethral
sphincter circumferentially, symmetrically bilaterally, asymmetrically unilaterally, anteriorly only, or posteriorly only, or
it can end bluntly above the sphincter [70]. Significant
overlap might render the preservation of the entire urethral
sphincter difficult.
Based on the above anatomy, Schlomm et al described a
full-length preservation of the urethral sphincter by
identifying and dissecting the distinct striated and smooth
muscle part of the sphincter inside the prostate apex until
the colliculus seminalis is encountered [69]. This technique
allows preservation of the entire length of the urethral
sphincter system irrespective of the apical shape. This
approach resulted in early continence results of 50% 1 wk
after catheter removal and 97% at 12 mo [69]. To date, it is
unclear whether dissection proximal to the colliculus
seminalis or just distal to the colliculus results in a
significant difference in the results [69,71], but full-length
preservation of the urethral sphincter up to the colliculus
seminalis clearly preserves a longer urethral sphincter and
thus may result in better continence.
4.
Conclusions
Recent focus on the anatomy of the prostate and its
surrounding tissue has produced expanded details applicable to surgical technique. Based on detailed anatomy and its
variations, the surgeon should individualise the dissection
in a patient according to cancer characteristics by altering
the technique to improve both oncologic and functional
Author contributions: Jochen Walz had full access to all the data in the
study and takes responsibility for the integrity of the data and the
accuracy of the data analysis.
Acquisition of data: Walz, Ganzer.
Analysis and interpretation of data: Walz, Epstein, Ganzer, Graefen,
Guazzoni, Kaouk, Menon, Mottrie, Myers, Patel, Tewari, Villers, Artibani.
Drafting of the manuscript: Walz.
Critical revision of the manuscript for important intellectual content: Walz,
Epstein, Ganzer, Graefen, Guazzoni, Kaouk, Menon, Mottrie, Myers, Patel,
Tewari, Villers, Artibani.
Statistical analysis: Walz.
Obtaining funding: None.
Administrative, technical, or material support: Walz, Villers, Tewari, Myers,
Patel.
Supervision: Artibani.
Other (specify): None.
Financial disclosures: Jochen Walz certifies that all conflicts of interest,
including specific financial interests and relationships and affiliations
relevant to the subject matter or materials discussed in the manuscript
(eg, employment/affiliation, grants or funding, consultancies, honoraria,
stock ownership or options, expert testimony, royalties, or patents filed,
received, or pending), are the following: None.
Funding/Support and role of the sponsor: None.
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