Blood Supply of Pelvis
The internal iliac (hypogastric) arteries supply the
greater part of the pelvic wall and pelvic organs. Subject to variations, these
arteries each divide into two major branches. The anterior branch gives off the
following arteries: obturator, inferior gluteal, umbilical, superior vesical,
middle vesical, inferior vesical, and internal pudendal, which supplies the
external genitalia.
The blood
supply of the bladder is derived from three arteries that enter it on each side
and anastomose freely. The superior vesical artery, supplying the bladder dome,
arises from the umbilical artery. The middle vesical artery, supplying the
bladder fundus and seminal vesicles, may originate from either the internal
iliac artery or a branch of the superior vesical artery. The inferior vesical
artery, which usually arises as a major division of the middle hemorrhoidal
artery, supplies the inferior portion of the bladder, the seminal vesicles, and
the prostate. The arterial blood supply to the vas deferens (deferential
artery) may rise from the superior vesical artery or from the inferior vesical
artery.
The
internal pudendal artery, which along with the gluteal artery stems from the
internal iliac, or hypogastric, artery, supplies the external genitalia. The vessel
courses downward and anteriorly to reach the lower portion of the greater
sciatic foramen where, at the lower border of the piriformis muscle, it leaves
the pelvis. In this region, the internal pudendal artery is adjacent to the
ischial spine under the cover of the gluteus maximus muscle. The artery then
passes through the sciatic foramen and enters the perineum, where it finally
divides into the perineal artery and the deep (cavernous) and dorsal arteries
of the penis. It is the internal pudendal perineal segment of the artery that may be injured
and result in vascular erectile dysfunction associated with long-term bicycle
use. After the artery enters the perineum, it courses upward and anteriorly
along the lateral wall of the ischiorectal fossa (Alcock canal), where it gives
off the inferior rectal artery.
The
prostatic blood supply is surgically relevant as “nerve-sparing” radical
prostatectomy procedures attempt to identify and avoid cavernous nerves associated
with these vessels to protect erectile function. The blood supply of the
prostate comes from the inferior vesical artery (branch of internal iliac
artery). The middle hemorrhoidal and internal pudendal arteries also send small
branches to the apical prostate. Within the prostate, two groups of arteries
are reliably observed. The internal or urethral groups supply approximately one
third of the prostatic mass and the urethra as far as the verumontanum. These
vessels penetrate the prostatic capsule at the prostaticovesical junction and
give off branches that enter and supply the lateral prostatic lobes
(illustrated in a case of hyperplasia). Inside the gland they proceed in a
perpendicular manner and reach the urethral lumen at the vesical orifice (neck)
at a location of 7 to 11 o’clock on the left and 1 to 5 o’clock on the right of
the orifice, as viewed cystoscopically. After the arteries pass these locations,
they turn distally and course parallel to the urethral surface beneath the
mucosa, supplying the prostatic urethra and also branching to the prostatic
tissue.
The
external or capsular arterial group supplies approximately two thirds of the
prostate. These vessels course along the posterolateral surface of the
prostate, where they are identified during prostatectomy surgery and give off branches
both ventrally and dorsally to supply the outer surface of the gland. Many
branches enter the prostatic capsule and anastomose to a moderate extent with
vessels of the urethral group. At the apex of the prostate, the capsular
arterial group penetrates inward to supply the urethra and that portion of the
prostate in the region of the verumontanum.
Venous
blood from the prostate drains through the puboprostatic and vesicoprostatic
(pudendal) plexus into
the vesical and hypogastric veins. This plexus spreads between the lower part
of the os pubis, the ventral surface of the bladder and the prostate, and
receives major contributions from the deep dorsal vein of the penis and
numerous prostatic veins to form the retropubic plexus of Santorini over the
prostatic capsule. Control of this venous plexus is critical to reduce lood
loss during radical prostatectomy procedures.
