Laparoscopic Anatomy Of The Male Pelvis

Bertrand Guillonneau, Karim A. Touijer, and Jeffery W. Saranchuk

Department of Urology, Sidney Kimmel Center for Prostate and Urologic Cancers, Memorial Sloan-Kettering Cancer Center, New York, New York, U.S.A.

■ INTRODUCTION

■ INTRA-ABDOMINAL ANATOMY OF THE PELVIS

The Bladder

The Medial Umbilical Ligament The Lateral Umbilical Ligament The Spermatic Cord The Iliac Vessels The Ureter

The Seminal Complex

The Rectum and Sigmoid Colon

■ THE RETROPUBIC SPACE The Pubis

The Obturator Muscles

The Bladder

The Endopelvic Fascia

The Santorini's Plexus

PROSTATIC FASCIA AND PROSTATIC

PEDICLES

The Visceral Fascia

The Denonvilliers' Fascia

Rectourethralis Muscle

The Prostatic Neurovascular Plexuses

SPHINCTERIC COMPLEX

The Rhabdomyosphincter

CONCLUSION

REFERENCES

INTRODUCTION

Anatomy is the key element to surgery. This is true for open or laparoscopic approach. Clear knowledge of anatomy is the "primum movens" of good surgical technique. In laparoscopy, the anatomical perspective of the surgical field is somewhat different from the one usually seen during open surgery. The magnification and the ease of access to the depths of the male pelvis bring into view anatomical details not fully described in currently available anatomy textbooks. To adapt and revise the anatomy incorporating this different perspective is thus a prerequisite to the realization of safe and efficient laparoscopic surgery. Furthermore, tactile feeling is somewhat diminished in laparoscopy and vision remains the primary fully available sense. Mastery of laparoscopic topographic anatomy is thus indispensable for visually identifying various structures and recognizing their spatial relationships with each other.

In this chapter we attempt to summarize our understanding of male pelvic anatomy from a laparoscopic standpoint.

INTRA-ABDOMINAL ANATOMY OF THE PELVIS

Upon entering the abdomen and visualizing the intra-abdominal pelvis, several structures are identifiable: the bladder and the median umbilical ligament in the mid-line, the medial and lateral umbilical ligament, and the spermatic vessels entering the deep inguinal ring more laterally (Fig. 1).

The Bladder

The bladder dome is median. It constitutes the mobile portion of the bladder, whose relationships change according to its state of distension. However, because a Foley catheter is routinely inserted into the bladder prior to creation of pneumoperitoneum, the bladder is empty and its anatomical boundaries are not visible at the inspection. To better delineate its limits, the bladder needs to be distended.

Once filled, the bladder visibly distends posteriorly, reduces the pouch of Douglas (also called rectovesical recess), and expands (i) laterally toward the medial umbilical ligament; (ii) anterosuperiorly underneath the anterior abdominal wall; and (iii) toward the umbilicus to which it is attached through the urachus.

FIGURE 1 ■ The umbilical ligaments. Transperitoneal view of the right half of the pelvis. Ureter (asterisk). Abbreviations: UL, umbilical ligament; MUL, medial umbilical ligament; LUL, lateral umbilical ligament; B, bladder; V, vas deferens; SV, spermatic vessels; EIV, external ilial vein.

FIGURE 2 ■ The pouch of Douglas. Abbreviations: B, bladder; V, vas deferens; U, ureter; IIA, internal ilial artery.

FIGURE 1 ■ The umbilical ligaments. Transperitoneal view of the right half of the pelvis. Ureter (asterisk). Abbreviations: UL, umbilical ligament; MUL, medial umbilical ligament; LUL, lateral umbilical ligament; B, bladder; V, vas deferens; SV, spermatic vessels; EIV, external ilial vein.

FIGURE 2 ■ The pouch of Douglas. Abbreviations: B, bladder; V, vas deferens; U, ureter; IIA, internal ilial artery.

The vesicular complex usually lies about 2 cm above the pouch of Douglas.

The medical umbilical ligament can be used as a guide to approach the pelvic ureter because at this level, the superior vesical artery crosses the ureter medially.

The umbilical fossa is divided in a superior and inferior portion by the vas deferens, providing access to the obturator fossa.

The urachus (median umbilical ligament) is visible along the anterior parietal peritoneum. It consists of a cord often accompanied by vessels that must be controlled when dividing the urachus. On either side, laterally, the median umbilical ligament is separated from the medial umbilical ligament by a peritoneal recess. The latter allows access to the vesical space (space of Retzious).

The pouch of Douglas (Fig. 2) appears as a cul-de-sac between the bladder anteriorly and the rectum posteriorly. Its depth varies among patients. Although in thin males the outline of the seminal vesicles and the distal portions of the vasa deferentia may be clearly visible through the visceral peritoneum covering the bladder posteriorly, most often the exact location of the vesicular complex is not visible. The vesicular complex usually lies about 2 cm above the pouch of Douglas.

The Medial Umbilical Ligament

The medial umbilical ligaments, the continuation of the obliterated hypogastric artery, are particularly easy to visualize in laparoscopy and represent an important anatomical landmark. The prominence of the medial umbilical ligament varies according to the amount of surrounding adipose tissue. The ligaments consist of an anteriorly tented cord between the umbilicus (superiorly) and the distal portion of the superior vesical artery branch of the internal iliac artery. At this anatomic location the hypogastric artery within the medial umbilical ligament is almost always completely obliterated, and does not bleed.

The medial umbilical ligament can be used as a guide to approach the pelvic ureter because at this level, the superior vesical artery crosses the ureter medially.

Laterally, the medial umbilical ligament is separated from the lateral umbilical ligament (fold of peritoneum covering the inferior epigastric artery) by the medial umbilical fossa.

The umbilical fossa is divided in a superior and inferior portion by the vas deferens, providing access to the obturator fossa.

The lateral umbilical ligament can be used as a guide to approach the external iliac vessels.

The Lateral Umbilical Ligament

The lateral umbilical ligament can be used as a guide to approach the external iliac vessels.

This ligament is the least pronounced of the three umbilical ligaments but its visualization is important for the insertion of the lower abdominal quadrant trocars. This ligament represents the peritoneal fold covering the inferior epigastric vessels. The inferior epigastric artery, a medial branch of the distal external iliac artery, ascends along the medial margin of the deep inguinal ring, continues between the rectus abdominis muscle and the posterior lamina of its sheath, and then raises the anterior parietal peritoneum creating the lateral umbilical ligament, which is crossed at its origin by the vas deferens superiorly.

The obturator fossa, a triangular area formed by the pubic rami with the obturator muscle, and the internal and external iliac vein as its sides, comprises an important lymphatic drainage zone for the prostate and the bladder, and represents the area to be dissected during pelvic lymphadenectomy.

The vas deferens and the medial umbilical ligament are major landmarks for pelvic lymph node dissection.

Transverse incision of the peritoneal fold about 2 cm above the base of the pouch of Douglas allows access to the seminal complex, and further distally to the Denonvilliers' fascia.

Dissection at the confluence of the internal and external vessels gives access to the superior vesical artery.

The genitofemoral nerve lies lateral to the external iliac artery. It can be used for nerve grafting after neurovascular bundle resection during radical prostatectomy.

The Spermatic Cord

The convergence of the spermatic vessels—spermatic artery and veins—and the vas deferens with its proper vessels forms the spermatic cord. The spermatic vessels course over the psoas-iliac muscle and are joined by the vas deferens before entering the deep inguinal ring.

The vas deferens, rarely visible behind the prostate even at its posterolateral aspect, becomes more superficial and visible laterally, covered with the parietal peritoneum where it crosses the external iliac vessels.

The vas deferens and the medial umbilical ligament are major landmarks for pelvic lymph node dissection.

In fact, a vertical incision of the parietal peritoneal fold across the vas deferens, in the medial umbilical fossa, leads to the external iliac vessels, with the artery located anterolaterally and superficially and the vein located posteromedially and more deeply.

The Iliac Vessels

Pulsations of the external iliac artery are usually seen through the overlying parietal peritoneum fold, at the level where the vas deferens joins the spermatic vessels.

The genitofemoral nerve lies lateral to the external iliac artery. It can be used for nerve grafting after neurovascular bundle resection during radical prostatectomy.

The external iliac vein, located medial to the external iliac artery, can be masked by a tortuous iliac artery. Furthermore, visualization of the vein may be impaired by the high-pressure pneumoperitoneum. In this situation, a reduction of the intra-abdominal pressure (5 mmHg) typically decompresses the iliac vein, bringing its gentle undulating pulsations into clear view.

To expose the external iliac vein, the parietal peritoneum directly overlying its medial aspect must be incised along the length of the vein. During such dissection, the surgeon should be aware of the presence of two medial venous branches. The first one, located proximally, or upstream, is the inconstant accessory circumflex vein, which reaches the external iliac vein just below the inferior aspect of the superior pubic ramus. The second branch, more distal, or downstream, is the internal iliac or hypogastric vein that runs in a posteroanterior orientation.

Dissection at the confluence of the internal and external vessels gives access to the superior vesical artery.

It should be noted that the left external iliac vessels are generally located somewhat more posteriorly, deeper in the pelvic cavity, as compared to the right external iliac vessels. As such, a laparoscopic left pelvic lymph node dissection may be technically somewhat more difficult.

The obturator nerve is located posteromedially to the external iliac vein. It appears as a white, shining, striated cord, usually flattened, entering the obturator fossa at the level of the convergence of the internal and external iliac veins, somewhat closer to the internal iliac vein. The obturator nerve enters the obturator canal at its superolateral edge. The nerve is accompanied by the obturator artery (branch of the internal iliac artery), and usually an obturator vein, which typically lies posterior to the nerve.

The obturator fossa, a triangular area formed by the pubic rami with the obturator muscle as its base, and the internal and external iliac vein as its sides, comprises an important lymphatic drainage zone for the prostate and the bladder, and represents the area to be dissected during pelvic lymphadenectomy.

The Ureter

The ureter crosses anteriorly over the common iliac vessels and can be readily identified at this level. The left ureter, covered by the parietal peritoneum and the pelvic mesocolon, remains medial to the internal iliac artery and crosses medially across the proximal part of the superior vesical artery before entering the bladder. Near its entrance in the detrusor, the ureter is also in the vicinity of the lateral aspect of the seminal vesicle, near the inferior hypogastric plexus (see The Seminal Complex).

The Seminal Complex

The distal portion of the two vasa deferentia, the ampullas, and the two seminal vesicles compose the seminal complex. This complex is rarely visible through the visceral peritoneal fold of the anterior aspect of the pouch of Douglas.

Transverse incision of the peritoneal fold about 2cm above the base of the pouch of Douglas allows access to the seminal complex, and further distally to the Denonvilliers' fascia (see The Denonvilliers' Fascia) (Fig. 3).

FIGURE3 ■ Transperitoneal view of the Denonvilliers' fascia after its opening through an incision of the anterior peritoneal fold of the pouch of Douglas. Anterior of the rectum recovered by fatty layer (asterisk). Abbreviations: SV, seminal vesicle; DF, Denonvilliers' fascia.

FIGURE3 ■ Transperitoneal view of the Denonvilliers' fascia after its opening through an incision of the anterior peritoneal fold of the pouch of Douglas. Anterior of the rectum recovered by fatty layer (asterisk). Abbreviations: SV, seminal vesicle; DF, Denonvilliers' fascia.

Transverse incision of the Denonvilliers' fascia exposes the seminal complex, where the vasa deferentia are identified laterally and ventrally. Anterior to each vas runs a deferential artery.

Trendelenburg positioning of the patient allows upward mobilization of the sigmoid colon by gravity, and access to the pouch of Douglas.

The superior portion of the Denonvilliers' fascia appears as a vertically striated tissue, covering the seminal complex posteriorly. Its dissection leads to the prerectal space with the adipose tissue on its proximal aspect.

Transverse incision of the Denonvilliers' fascia exposes the seminal complex, where the vasa deferentia are identified laterally and ventrally. Anterior to each vas runs a deferential artery.

The seminal vesicles, whose size varies physiologically, lie posteriorly, inferiorly, and laterally to the vas. The posterior aspect of the seminal vesicle is easy to dissect from the prostatorectal fascia. The anterior aspect of the tip of the seminal vesicle is traversed by the seminal vesicular artery, often a sizable blood vessel, which is a branch of the superior vesical artery. The lateral aspect and tip of the seminal vesicle is in close relationship with the inferior hypogastric plexus also known as the pelvic plexus, which carries innervating fibers to the pelvis (1). The inferior hypogastric plexus measures about 40 mm in height, 10 mm in width and 3 mm in thickness, and is molded to the contours of the seminal vesicle as far as the vesiculoprostatic junction. The inferior hypogastric plexus receives afferent fibers from the superior hypogastric plexus-or preaortic plexus (sympathic fibers arising from the thoracic region) and from the pelvic splanchnic nerves-or erector nerves, nervi erigentes (parasympathetic preganglionic fibers arising from the sacral plexus S2 to S4). The cavernous nerves emerge at the level of the anteroinferior border of the inferior hypogastric plexus.

The Rectum and Sigmoid Colon

Only the superior half or superior third of the rectum is visible during pelvic laparo-scopic surgery.

Trendelenburg positioning of the patient allows upward mobilization of the sig-moid colon by gravity, and access to the pouch of Douglas.

The sigmoid colon is attached by the sigmoid mesocolon to the left lateral aspect of the pelvis, overlying the left external iliac vessels.

THE RETROPUBIC SPACE

The retropubic or prevesical space can be approached laparoscopically either transperi-toneally or extraperitoneally. The retropubic space has a triangular shape, limited (i) anteriorly by the pubis and the fascia transversalis covering the posterior surface of the anterior abdominal wall; (ii) posteriorly by the bladder through the umbilicoprevesical fascia and the endopelvic fascia; and (iii) laterally by the internal obturator muscles.

The Pubis

The superior ramus of pubis is covered witha fascia that thickens laterally, forming Cooper's ligament.

The Obturator Muscles

On each side of the pelvis, the obturator muscle is tented between the ischial spine and the inferior border of the pubic ramus, and is supported inferiorly by the tendinous arch

A branch of the inferior vesical artery joins the prostatic pedicle, gives origin to the prostatic arteries, the vesicular arteries, the deferential arteries, and the arteries running along the cavernous nerves forming the so-called "neurovascular bundle."

The lateral recess of the endopelvic fascia constitutes a weak part of the endopelvic fascia that is incised to approach the lateral aspect of the prostate.

In some patients, an accessory pudental artery branch of the obturator artery, can be seen on the superior surface of the endopelvic fascia and should be preserved because it may represent the single major source of vascularization to the corpus cavernosum.

The puboprostatic ligaments are not vascularized and can be cut safely at their most anterior portion.

of the levator ani muscle. The muscle covers the obturator foramen, yielding, laterally and anteriorly, the passage of the obturator pedicle through the obturator canal.

The Bladder

The bladder is covered with a layer of fat that can be dissected easily off the detrusor. Therefore, there are two spaces of dissection that can be developed. The first one is close to the bladder wall, between the detrusor and the layer of perivesical fat. The second, corresponding to the Retzius space, is more anterior, between the layer of perivesical fat and the posterior aponeurosis of the rectus sheath, up to the arcuate line or aponeurosis of Douglas.

Laterally, the bladder is attached to the pelvic cavity through the vesical ligament, which, from top to bottom, carries the superior vesical artery and veins (a branch of which is obliterated and becomes the median umbilical ligament), the distal portion of the ureter, and (inferiorly) the inferior vesical veins and artery.

Abranch of the inferior vesical artery joins the prostatic pedicle, gives origin to the prostatic arteries, the vesicular arteries, the deferential arteries, and the arteries running along the cavernous nerves forming the so-called "neurovascular bundle."

The Endopelvic Fascia

The endopelvic fascia is the inferior limit of the Retzius space. It is stretched between the tendinous arches of the levator ani muscle, and covers the anterior aspect of the prostate.

Laterally, the endopelvic fascia presents two recesses—or sulci—situated between the prostate medially and the pelvic muscles laterally.

The lateral recess of the endopelvic fascia constitutes a weak part of the endopelvic fascia that is incised to approach the lateral aspect of the prostate.

The endopelvic fascia recess is particularly weak and thin toward the prostate base, and anteriorly toward the apex where it is fenestrated between lateral expansions of the puboprostatic ligaments.

In some patients, an accessory pudental artery branch of the obturator artery, can be seen on the superior surface of the endopelvic fascia and should be preserved because it may represent the single major source of vascularization to the corpus cavernosum. (2)

The incision of the endopelvic fascia should start proximally, because there is a paucity of blood vessels at that level. This incision uncovers the medial aspect of the lev-ator ani muscle, below the tendinous arch. In some patients, the dissection may be conducted medially up to the parietal fascia of this muscle, but most often the dissection has to be more lateral, leaving the levator ani fascia on the prostate. Inferiorly, this fascia fuses with the lateral aspect of the Denonvilliers' fascia in the area of the neurovascular bundle.

More laterally and anteriorly, posterior and inferior to the lateral oblique extension of the puboprostatic ligament, veins running from the levator ani muscle to the superolateral aspect of the prostatic apex may be identified. More specifically, it is not unusual to find an artery coming through the fibers of the levator ani muscle and running to the superolateral aspect of the prostatic apex where it turns toward the venous complex after giving a branch(es) to the apex.

Anteriorly, the puboprostatic ligaments are a condensation of the endopelvic fascia attached to the inferior border of the inferior pubic ramus. On each side, the pub-oprostatic ligament is either single and vertical or multiple with often a lateral oblique extension (Fig. 4). In the sagittal plane, the most medial ligament does not appear as a cord tended between the pubis and the prostatic apex, but more as a fold that is in continuity with the transverse perineal ligament (arcuate pubic ligament). Histologically, it has been shown that the puboprostatic ligaments are detrusor muscle extensions (detrusor apron) that partially cover the anterior surface of the prostate, hence the name pubovesical ligaments (3).

Between the two puboprostatic ligaments emerges the superficial dorsal vein separated from the deep venous complex by a plane easy to develop. Frequently, the superficial dorsal vein runs within the fat covering the anterior layer of the endopelvic fascia and gives multiple branches at the level of the vesicoprostatic junction where it enters the detrusor muscle. In some patients, the deep dorsal vein bifurcates or trifurcates immediately after its entrance into the pelvis. The puboprostatic ligaments are not vas-cularized and can be cut safely at their most anterior portion.

Laterally, the puboprostatic ligament fuses with the extension of the parietal fascia of the levator ani and the visceral prostatic fascia, creating a relatively thick "sphinc-teric" fascia that covers the lateral aspect of the deep venous complex. More posteriorly, this sphincteric fascia covers the ischioprostatic ligaments—or Muller's ligaments or

FIGURE 4 ■ The puboprostatic ligaments. View of the Retzius space showing the fat covering the anterior aspect of the endopelvic fascia. Main puboprostatic ligaments (asterisks) and superficial dorsal vein (circle).

FIGURE 4 ■ The puboprostatic ligaments. View of the Retzius space showing the fat covering the anterior aspect of the endopelvic fascia. Main puboprostatic ligaments (asterisks) and superficial dorsal vein (circle).

An "interfascial" dissection conducted between the prostate capsule and the prostate visceral fascia leaves the neurovascular bundle totally intact and surrounded by its fascia.

Walsh's pillars—which anchor the rhabdomyosphincter and the sphincteric membranous urethra to the bony structures.

Posteriorly, the endopelvic fascia becomes attenuated and merges with the detrusor muscle.

The Santorini's Plexus

The Santorini's plexus is composed of the superficial dorsal vein (described above) and the so-called or deep venous complex (Fig. 5). In fact, this complex is composed of large veins draining the penis, and one or two arteries. It may seem therefore more appropriate to name this complex the "deep vascular complex."

Posteriorly, the deep venous complex is separated from the anterior surface of the urethra by an avascular plane that can be developed easily as it extends cephalad, the deep venous complex branches into a network of veins on the anterior aspect of the prostate. Some branches penetrate the prostatic apron and drain into the prostatic pedicular veins. Others drain directly into the pudendal veins along the neurovascular bundles (4).

PROSTATIC FASCIA AND PROSTATIC PEDICLES The Visceral Fascia

The visceral fascia covers the external surface of the prostate, bladder, and seminal vesicles.

Along the posterolateral surface of the prostate, the visceral fascia is in continuation with the Denonvilliers' fascia, and its dissection off the prostatic capsule delineates the medial surface of the neurovascular bundle.

An "interfascial" dissection conducted between the prostate capsule and the prostate visceral fascia leaves the neurovascular bundle totally intact and surrounded by its fascia.

With this approach the cavernous nerves, the vessels of the bundle, and the fatty tissue embedding them all are not directly seen. As mentioned, it seems appropriate to name this dissection as the "interfascial" neurovascular bundle dissection, as opposed to the "extrafascial" dissection where the dissection is performed with variable width into the neurovascular bundle itself (5). The term "intrafascial" dissection would imply that the plane of dissection is developed between the prostatic parenchyma and the capsule, an oncologically inappropriate plane of dissection.

Distally, the fusion of the visceral fascia with the inferior extension of the pubopro-static fascia and the parietal fascia of the levator ani muscle forms the "sphincteric" fascia that recovers laterally the deep venous complex and the ischioprostatic ligaments.

The Denonvilliers' Fascia

This fascia has several terminologies. It is variously known as "posterior prosta-torectal fascia," "septum rectovesicale," or "prostatoseminal vesicular fascia." To comply with common custom, the eponym terminology, "Denonvilliers' fascia," will be used here. The Denonvilliers' fascia is posterior to the prostate and anterior to the rectum. Superiorly, it surrounds the seminal vesicles where it fuses with the usual visceral fascia. On the anterior aspect of the seminal vesicle, the Denonvilliers'

FIGURE5 ■ Apex of the prostate. The Santorini's plexus has been ligated and divided. Periurethral fascia (asterisks). Abbreviations: DVC, deep vascular complex; U, sphincteric urethra; PA, prostatic apex.

FIGURE 6 ■ Right neurovascular bundle recovered by its fascia, fusion of the prostatic visceral fascia and the Denonvilliers' fascia. Urethra (asterisk). Abbreviations: P, prostate; LA, levator ani muscle; O, obturator muscle; TA, tendinous arch of the levator ani muscle; R, rectum.

FIGURE5 ■ Apex of the prostate. The Santorini's plexus has been ligated and divided. Periurethral fascia (asterisks). Abbreviations: DVC, deep vascular complex; U, sphincteric urethra; PA, prostatic apex.

FIGURE 6 ■ Right neurovascular bundle recovered by its fascia, fusion of the prostatic visceral fascia and the Denonvilliers' fascia. Urethra (asterisk). Abbreviations: P, prostate; LA, levator ani muscle; O, obturator muscle; TA, tendinous arch of the levator ani muscle; R, rectum.

The Denonvilliers' fascia can be closely adherent to the prostatic gland and at risk of malignant involvement in patients with invasive prostate cancer. Thus, the Denonvilliers' fascia should be posteriorly removed en bloc with the radical prostatectomy specimen.

fascia merges with a prostatic extension of the detrusor and becomes multilayered and rich with muscular fibers. Inferiorly, it merges with the expansion of the rec-tourethralis muscle, posteriorly to the sphincteric-membranous urethra. Laterally, it merges with the lateral fold of the visceral fascia, determining the superomedial and inferomedial borders of the neurovascular bundle (Fig. 6).

The Denonvilliers' fascia is more adherent to the prostate than to the rectum, particularly on its superior aspect where it is separated from the rectum by a layer of fatty tissue. Distally, this layer of adipose tissue fades and the Denonvilliers' fascia becomes much more adherent to the rectal wall.

The Denonvilliers' fascia can be closely adherent to the prostatic gland and at risk of malignant involvement in patientswith invasive prostate cancer. Thus, the Denonvilliers' fascia should be posteriorly removed en bloc with the radical prostatectomy specimen (6).

Rectourethralis Muscle

The rectourethralis is a Y-shaped muscle arising within the substance of the rectal wall deep to the outer longitudinal smooth muscle and inserts into the central tendon of the perineum. As such, this structure is rarely encountered in laparoscopy (7). It is currently accepted that the Denonvilliers' fascia inserts distally on the rectourethralis muscle, merging with it.

The Prostatic Neurovascular Plexuses

The prostatic neurovascular plexus contains veins, arteries and autonomic nerves. Its limits are the parietal fascia of the levator ani laterally, and the fusion of the Denonvilliers' fascia and the prostatic visceral fascia medially.

The Cavernous Nerves

The cavernous nerves arise from the inferior hypogastric plexus and contain auto-nomic, sympathetic and parasympathetic fibers. These nerves appear like a network distributed to the prostate and to the corpus cavernosum. The nerves join the prostatic artery at the level of the pedicle. The cavernous branches of the network then follow the posterolateral aspect of the prostate toward the apex, accompanied by veins and arterial branches of the prostatic pedicular artery (8). Apically, the nerves run more postero-medially to the prostate. Along their course, small branches of the cavernous nerves penetrate the prostate capsule (intracapsular nerves). However, visualization of these branching nerves is difficult, even during the laparoscopic "interfascial" dissection. Nonetheless, their existence is confirmed by pathological studies (9).

The Arteries

The arteries are very visible during laparoscopic dissection and are important landmarks for initiating the dissection plane of the "interfascial" neurovascular

FIGURE 7 ■ Right prostatic pedicle. Main prostatic pedicular artery (asterisk). Abbreviation: PPF, periprostatic fascia.

FIGURE 7 ■ Right prostatic pedicle. Main prostatic pedicular artery (asterisk). Abbreviation: PPF, periprostatic fascia.

A vein originating from the deep venous complex and running along the anterior tip of the crescent shape neurovascular bundle can be used as a landmark for the neurovascular preservation.

dissection (Fig. 7). At the level of the arborescence of the prostatic arteries into prostatic, vesicular, and deferential arteries, at least one branch runs anteroinferi-orly on the lateral aspect of the base of prostate and joins the cavernous nerves to form the neurovascular bundle posterolaterally. Once within the neurovascular bundle, the artery generates an arterial network. Rarely, one of these arteries crosses the medial visceral fascia to enter the prostatic capsule at the mid portion of the gland. More often the arteries run all along the prostate and only give a retrograde branch to the apex.

The Veins

A vein originating from the deep venous complex and running along the anterior tip of the crescent shape neurovascular bundle can be used as a landmark for the neurovascu-lar preservation.

Although the veins usually follow the course of the artery, it is not infrequent in the case of a large vein originating from the deep venous complex and running along the anterior tip of the crescent shape neurovascular bundle.

The length of the sphincteric urethra measured by magnetic resonance imaging is variable among individuals (between 6 and 24 mm; average, 14 mm) and seems to be directly related to the recovery of continence.

Extrapudendal nerves can sometimes be found inside the pelvis and may be damaged during pelvic surgery.

SPHINCTERIC COMPLEX The Rhabdomyosphincter

Urinary continence relies on a combined function of detrusor, trigone, and urethral sphincter muscles.The external urethral sphincter covers the ventral surface of the prostate as a crescent shape above the veru montanum, assumes a horseshoe shape below the veru montanum, and then becomes more crescent shaped along the proximal bulbar urethra. The levator ani muscles form an open circle around the external sphincter with a hiatus at the ventral aspect. The smooth and striated muscle components of the urethral sphincteric complex are inseparable (10).

The length of the sphincteric urethra measured by magnetic resonance imaging is variable among individuals (between 6 and 24 mm; average, 14 mm) and seems to be directly related to the recover of continence (11).

Innervation of the Rhabdomyosphincter

The innervation of the so-called "rhabdomyosphincter" is supported mainly by fibers coming from the S2 to S4 roots and traveling via the pudental nerve. These nerves are not visualized during a laparoscopic pelvic surgery because they run posterolateral to the rectum, and then inferior to the levator ani muscle. More distally the main trunk gives terminal branches to the inferolateral aspect of the ure-thral sphincter.

Extrapudendal nerves can sometimes be found inside the pelvis and may be damaged during pelvic surgery (12,13).

Rhabdomyosphincteric innervation by branches arising from the pelvic plexus (S4 root) have also been described as a branch of the pelvic splanchnic nerve. They also are posterolateral to the rectum and are not visible during a pelvic dissection for urologic disease (14).

CONCLUSION

The understanding of anatomy is ever evolving. Laparoscopy with its inherent limitations and advantages necessitates a somewhat different comprehension of the surgical anatomy, adapted to a certain angle of vision and magnification. There is no doubt that the knowledge of the laparoscopic anatomy of the pelvis will grow over time, and will allow surgery to reach its ultimate goal: being curative without being deleterious.

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