Blood Supply of Testis
The internal spermatic artery originates from the
abdominal aorta just below the renal artery. Embryo- logically, the testicles
lie opposite the second lumbar vertebra and keep the blood supply that is
acquired during the first weeks of life as they descend into the scrotum. The
internal spermatic artery joins the spermatic cord above the internal inguinal
ring and lies adjacent to the testicular veins (pampiniform plexus) to the
testis mediastinum. Inferior to the scrotal pampiniform plexus, the spermatic
artery is highly coiled and branches before entering the testis. Extensive
interconnections, especially between the internal spermatic and deferential
arteries, allow maintenance of testis viability even after division of the
internal spermatic artery. A single artery enters the testis in 56% of cases;
two branches enter in 31% of cases and three or more branches in 13% of testes.
In men with a single testicular artery, its interruption can result in
testicular atrophy. The testicular arteries penetrate the testis tunica albuginea
and travel inferiorly along its posterior surface and penetrate into the
parenchyma. Individual arteries to the seminiferous tubules, termed centrifugal
arteries, travel within the septa between tubules. Centrifugal artery branches give
rise to arterioles that become individual intertubular and peritubular
capillaries.
The
deferential artery (artery of the vas deferens) originates from either the
inferior or superior vesical artery (see Plate 2-6) and supplies the vas
deferens and the cauda of the epididymis. Near the testis, the internal
spermatic artery and the deferential artery anastomose. A third artery, the
external spermatic artery (cremasteric artery), arises from the inferior
epigastric artery from within the internal inguinal ring, where it enters the
spermatic cord. This artery forms a network over the tunica vaginalis and
usually anastomoses at the testicular mediastinum with the internal spermatic
and deferential arteries. The external spermatic artery also forms anastomotic
patterns that supply the scrotal wall. The veins of the spermatic cord emerge
from the testis mediastinum to form the extensive pampiniform plexus. These
veins gradually coalesce and, in 60% of cases, form a single trunk within the
inguinal canal. The pampiniform plexus consists of three groups of freely
anastomosing veins: (1) the internal spermatic vein group that emerges from the
testicle and accompanies the spermatic artery to enter the vena cava; (2) the
deferential group that accompanies the vas deferens to veins within the pelvis;
and (3) the external spermatic (cremasteric) group that follows a course along
the posterior spermatic cord. The latter group empties into branches of the
superficial and deep inferior epigastric veins and into the superficial external
and deep pudendal veins. These groups of veins afford routes of collateral
circulation for blood return from the testicles.
The right
internal spermatic vein enters the inferior vena cava obliquely below the right
renal vein, whereas the left internal spermatic vein terminates in the left
renal vein at a right angle, apparently without natural valve formation. These
differences in drainage patterns likely explain the fact that 95% per cent of
varicoceles
occur on
the left side, where natural resistance to increased abdominal pressure on
retrograde flow through these veins is lower.
With
varicocele formation, blood flow in the internal spermatic vein is reversed.
With varicocelectomy, all veins except the deferential veins are ligated to
reverse this process and improve pain or testis function. The deferential vein
affords a sufficient avenue for blood return. When performed in the
retroperitoneum (Palomo
or laparoscopic), varicocele recurrence rates after surgery are higher than
when performed inguinally or subinguinally because of more complete ligation of
all suspicious contributing veins observed more distally. Because of the
increased number of pampiniform plexus veins subinguinally and the potential lack
of a sufficiently collateralized arterial supply, varicocelectomy at this
anatomic level is performed microscopically.
