Tuesday, August 12, 2008

Arterial Supply

Major arteries of the pelvis are summarized in Table 2-1 . At the bifurcation of the aorta, the middle sacral artery arises posteriorly and travels on the pelvic surface of the sacrum to supply branches to the sacral foramina and the rectum. The common iliac arteries arise at the level of the fourth lumbar vertebra, run anterior and lateral to their accompanying veins, and bifurcate into the external and internal iliac arteries at the SI joint ( Fig. 2-15 ). The external iliac artery follows the medial border of the iliopsoas muscle along the arcuate line and leaves the pelvis beneath the inguinal ligament as the femoral artery ( Fig. 2-16 ). Its inferior epigastric artery is given off proximal to the inguinal ligament and ascends medial to the internal inguinal ring to supply the rectus muscle and overlying skin. Because the rectus is richly collateralized from above and laterally, the inferior epigastric arteries may be ligated with impunity. A rectus myocutaneous flap based on this artery has been used to correct major pelvic and perineal tissue defects. Near its origin, the inferior epigastric artery sends a deep circumflex iliac branch laterally and a pubic branch medially. Both vessels travel on the iliopubic tract and may be injured during inguinal hernia repair. Its cremasteric branch joins the spermatic cord at the internal inguinal ring and forms a distal anastomosis with the testicular artery (see Fig. 2-44 ). In 25% of people, an accessory obturator artery arises from the inferior epigastric artery and runs medial to the femoral vein to reach the obturator canal. This vessel must be avoided during obturator lymph node dissection.

Table 2-1 -- Arteries of the Pelvis
Artery Name Origin Supplies
Middle sacral Aorta Sacral nerves and sacrum
External Iliac Branches
Inferior epigastric External iliac Rectus abdominis muscle and overlying skin and fascia
Deep circumflex iliac Inferior epigastric Inguinal ligament and surrounding structures laterally
Pubic Inferior epigastric Inguinal ligament and surrounding structures medially
Cremasteric Inferior epigastric Vas deferens and testis
Internal Iliac Branches
Superior gluteal Posterior trunk Gluteus muscles and overlying skin
Ascending lumbar Posterior trunk Psoas and quadratus lumborum muscles and adjacent structures
Lateral sacral Posterior trunk Sacral nerves and sacrum
Superior vesical Anterior trunk Bladder, ureter, vas deferens, and seminal vesicle
Middle rectal Anterior trunk Rectum, ureter, and bladder
Inferior vesicle Anterior trunk Bladder, seminal vesicle, prostate, ureter, and the neurovascular bundle
Uterine Anterior trunk Uterus, bladder, and ureter
Internal pudendal Anterior trunk Rectum, perineum, and external genitalia
Obturator Anterior trunk Adductor muscles of the leg and overlying skin
Inferior gluteal Anterior trunk Gluteus muscles and overlying skin

Figure 2-15 Right internal and external iliac arteries. The ureter and vas deferens pass medial to the vessels. (From Clemente CD: Gray's Anatomy, 30th American ed. Philadelphia, Lea & Febiger, 1985, p 750.)

Figure 2-16 Right obturator fossa, showing the iliac vessels and obturator nerve. (From Skinner DG: Pelvic lymphadenectomy. In Glenn JF [ed]: Urological Surgery, 2nd ed. New York, Harper & Row, 1975, p 591.)

Figure 2-44 Collateral arterial circulation to the testis. (From Hinman F Jr: Atlas of Urosurgical Anatomy. Philadelphia, WB Saunders, 1993, p 497.)

The internal iliac (hypogastric) artery descends in front of the SI joint and divides into an anterior and a posterior trunk (see Fig. 2-15 ). The posterior trunk gives rise to three parietal branches: (1) the superior gluteal, which exits the greater sciatic foramen; (2) the ascending lumbar, which supplies the posterior abdominal wall; and (3) the lateral sacral, which passes medially to join the middle sacral branches at the sciatic foramina.

The anterior trunk gives off seven parietal and visceral branches: (1) The superior vesical artery arises from the proximal portion of the obliterated umbilical artery and gives off a vesiculodeferential branch to the seminal vesicles and vas deferens. The artery of the vas deferens travels the length of the vas to meet the cremasteric and testicular arteries distally (see Fig. 2-44 ). Because of these anastomoses, the testicular artery may be sacrificed without compromising the viability of the testis. (2) The middle rectal artery gives small branches to the seminal vesicles and prostate and anastomoses with the inferior and superior rectal arteries in the rectal wall. (3) The inferior vesical branches supply the lower ureter, the bladder base, the prostate, and the seminal vesicles. In the female, they supply the ureter, the bladder base, and the vagina. (4) The uterine artery passes above and in front of the ureter (“water flows under the bridge”) to ascend the lateral wall of the uterus and meet the ovarian artery in the lateral portion of the fallopian tube (see Figs. 2-13 and 2-31 [13] [31]). The ureter is vulnerable during division of the uterine pedicles. (5) The internal pudendal artery leaves the pelvic cavity through the greater sciatic foramen, passes around the sacrospinous ligament, and enters the lesser sciatic foramen to gain access to the perineum. Its perineal course is discussed later. (6) The obturator artery, variable in origin, travels through the obturator fossa medial and inferior to the obturator nerve and passes through its canal to supply the adductors of the thigh (see Fig. 2-16 ). (7) The inferior gluteal artery travels through the greater sciatic foramen to supply the buttock and thigh.

Figure 2-31 Female internal genitalia, from behind. The ureter passes beneath the uterine artery. (From Hinman F Jr: Atlas of Urosurgical Anatomy. Philadelphia, WB Saunders, 1993, p 402.)

The internal iliac artery can be ligated to control severe pelvic hemorrhage. Ligation decreases the pulse pressure, allowing hemostasis to occur more readily. Internal iliac blood flow does not stop but reverses its direction because of critical anastomoses (lumbar segmentals to iliolumbar; median sacral to lateral sacral; and superior rectal and middle rectal). Bilateral ligation almost invariably produces vasculogenic impotence.

Venous Supply

The dorsal vein of the penis passes between the inferior pubic arch and the striated urinary sphincter to reach the pelvis, where it trifurcates into a central superficial branch and two lateral plexuses ( Reiner and Walsh, 1979 ) ( Fig. 2-17 ). To minimize blood loss at radical retropubic prostatectomy, the dorsal vein complex is best divided distally, before its ramification. Part of this complex runs within the anterior and lateral wall of the striated sphincter; thus, care must be taken not to injure the sphincter when securing hemostasis. The superficial branch pierces the visceral endopelvic fascia between the puboprostatic ligaments and drains the retropubic fat, the anterior bladder, and the anterior prostate (see Figs. 2-17 and 2-40 [17] [40]).

Figure 2-17 Pelvic venous plexus. A, Trifurcation of the dorsal vein of the penis, viewed from the retropubic space. The relationship of the venous branches to the puboprostatic ligaments is shown. B, Lateral view of the pelvic venous plexus after removal of the lateral pelvic fascia. Normally these structures are difficult to see because they are embedded in pelvic fascia. (From Reiner WG, Walsh PC: An anatomical approach to the surgical management of the dorsal vein and Santorini's plexus during radical retropubic surgery. J Urol 1979;121:198-200.)

The lateral plexuses sweep down the sides of the prostate, receiving drainage from it and the rectum, and communicate with the vesical plexuses on the lower part of the bladder. Three to five inferior vesical veins emerge from the vesical plexus laterally and drain into the internal iliac vein. In the female, the dorsal vein of the clitoris bifurcates to empty into the laterally placed vaginal plexuses. These connect with the vesical, uterine, ovarian, and rectal plexuses and drain into the internal iliac veins. Connections between the pelvic plexuses, the emissary veins of the pelvic bones, and the vertebral plexus have been proposed to be routes for the dissemination of infection or tumor from the pelvic viscera to the axial and pelvic skeleton ( Batson, 1940 ).

The internal iliac vein is joined by tributaries corresponding to the branches of the internal iliac artery and ascends medial and posterior to the artery. This vein is relatively thin walled and at risk for injury during dissection of the artery or the nearby pelvic ureter. The external iliac vein travels medial and inferior to its artery and joins the internal iliac vein behind the internal iliac artery. In half the patients, one or more accessory obturator veins drain into the underside of the external iliac vein and can be easily torn during lymphadenectomy (see Fig. 2-16 ).

Pelvic Lymphatics

The pelvic lymph nodes can be difficult to appreciate on gross examination because they are embedded in the fatty and fibrous tissue of the intermediate stratum. Three major lymph node groups are associated with the pelvic vessels ( Fig. 2-18 ). A substantial portion of pelvic visceral lymphatic drainage passes through the internal iliac nodes and their tributaries: the presacral, obturator, and internal pudendal nodes. The external iliac nodes lie lateral, anterior, and medial to the vessels and drain the anterior abdominal wall, urachus, bladder, and, in part, internal genitalia. The external genitalia and perineum drain into the superficial and deep inguinal nodes (see later discussion). The inguinal nodes communicate directly with the internal and external iliac chains. The common iliac nodes receive efferent vessels from the external and internal iliac nodes and the pelvic ureter and drain into the lateral aortic nodes.

Figure 2-18 Lymphatic drainage of the male pelvis, perineum, and external genitalia.

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