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.