The Retroperitoneum

The distribution of metastases from each testis to the retroperitoneal lymph nodes has been described defin-itively.7 The technique of retroperitoneal lymph node dissection is the topic of a subsequent chapter (see Chapter 10) and will not be addressed here. Rather, the major blood vessels and the autonomic nerve supply of the retroperitoneum will be discussed.

Blood Supply

The abdominal aorta passes through the diaphragm at the level of the twelfth thoracic vertebra and lies in front of the anterior longitudinal ligament that covers the lumbar vertebrae.4 It divides into two common iliac arteries at the fourth lumbar vertebra. The branches of the abdominal aorta may be divided into paired arteries to the body wall, arteries to paired viscera, and unpaired midline branches to the digestive tract (Figure 3-6).4

The body wall branches are segmental arteries in series with the posterior intercostal branches of the thoracic aorta.4 The inferior phrenic arteries supply the diaphragm and may send a branch to the adrenal gland. There are four pairs of lumbar arteries, which arise from the posterior abdominal aorta at the bodies of the four upper lumbar vertebrae. They pass laterally and posteriorly against the bodies of the vertebrae, posterior to the sympathetic trunk and posterior to the inferior vena cava on the right side as well.4 The anterior branches of the lumbar arteries are small and barely extend beyond the lateral border of the muscu-lus quadratus lumborum. Each artery also has a large posterior branch that accompanies the dorsal ramus of the corresponding spinal nerve and divides into spinal and muscular branches. The spinal branch passes through the intervertebral foramen and supplies the

Inferior phrenic a.

Celiac trunk Suprarenal a.

Lumbar a LeN renal a.

Inferior phrenic a.

Celiac Trunk Divides Into

Celiac trunk Suprarenal a.

Lumbar a LeN renal a.

Figure 3-6. Branches of the abdominal aorta. (Reproduced with permission from Hall-Craggs EC.4)

Figure 3-6. Branches of the abdominal aorta. (Reproduced with permission from Hall-Craggs EC.4)

spinal cord, the meninges, and the vertebrae.2 The large muscular branches supply the muscles of the back and the overlying skin and subcutaneous tissues. Because of extensive collateral circulation in the younger age group of men undergoing retroperitoneal lymph node dissection, sacrifice of the lumbar arteries has not been associated with adverse neurologic sequelae to the spinal cord itself.

Branches of the abdominal aorta to paired viscera are the middle adrenal (suprarenal) arteries, the renal arteries, and the gonadal arteries to the testes. The suprarenal arteries supply the adrenal glands directly from the aorta.1 The renal arteries arise just below the level of the superior mesenteric artery. The right artery passes behind the inferior vena cava and right renal vein to the kidney. The shorter left renal artery passes posterior to the left renal vein. Small inferior adrenal branches are given off by both arteries.

Figure 3-1 illustrated the embryologic development of the lateral branches of the abdominal aorta. Lateral sprouts vascularize the adrenal glands, the testes, and the kidneys. At about the sixth week, the gonads begin to descend while the kidneys ascend. The gonadal artery lengthens as the testis descends, but the ascending kidney is vascularized by a series of new and more-cephalad sprouts from the aorta (see Figure 3-1). This complex process largely explains why variations in the number and location of renal arteries and veins are so common. This variability in renal vasculature often presents one of the most challenging aspects of retroperitoneal lymph node dissection.

The unpaired branches of the abdominal aorta to the digestive tract are the celiac trunk, the superior mesenteric artery, and the inferior mesenteric artery. It is the superior mesenteric artery that limits the upward extent of retroperitoneal lymph node dissection. This artery supplies the whole length of the small intestine as well as the ascending and transverse colon.2 Injury to this vessel is catastrophic. The inferior mesenteric artery supplies the descending and sigmoid flexure of the colon and most of the rectum.2

There is extensive collateral circulation in these areas of the bowel, so the inferior mesenteric artery may be sacrificed in more extensive dissections, without adverse consequences.

The inferior vena cava is formed to the right of and behind the bifurcation of the aorta, by the junction of the two common iliac veins. The tributaries of the inferior vena cava do not correspond to those of the aorta in several respects.4 There are no veins from the digestive tract since these drain into the hepatic portal system. Only the right gonadal vein drains directly into the inferior vena cava; the left gonadal vein drains into the left renal vein. Lastly, the short hepatic veins drain directly into the inferior vena cava posterior to the liver.

Autonomic Innervation of the Retroperitoneum and Pelvic Viscera

Sympathetic innervation to the pelvic viscera arises from spinal segments T12 to L2 (Figure 3-7).4 White rami communicantes carry the preganglionic sympathetic motor neurons from the lowest thoracic and upper lumbar spinal nerves to the sympathetic chain of paravertebral ganglia.4 Some of the neurons

Sympathetic Chain
Figure 3-7. Autonomic innervation of the pelvic viscera. Visceral afferent fibers are shown as dashed lines. (Reproduced with permission from April EW.5)

may synapse within the paravertebral ganglia before leaving via the lumbar splanchic nerves to join the aortic plexus. The superior hypogastric plexus is the continuation of the aortic plexus; injury to this plexus results in retrograde ejaculation.

The superior hypogastric plexus consists of a broad flattened band of intercommunicating nerve bundles that descend over the bifurcation of the aorta.3 The relationship of the plexus to the aorta and vena cava is shown in Figure 3-8.8 Opposite the first sacral segment, the plexus divides into left and right hypogastric nerves. There are few (if any) parasympathetic neurons in the superior hypogastric plexus. The hypogastric nerves (also called the inferior hypogastric plexuses) run along the anterior surface of the sacrum to provide sympathetic innervation to the pelvic plexus on the walls of the rectum.

Parasympathetic innervation to the pelvic viscera arises from spinal segments S2 to S4.4 The pelvic splanchnic nerves represent the sacral portion of the craniosacral (parasympathetic) portion of the auto-nomic nervous system.4

Craniosacral System Anatomy
Figure 3-8. Anatomy of retroperitoneal sympathetic fibers. (Reproduced with permission from Foster RS, Donohue JP.8

These preganglionic nerves supply the parasym-pathetic innervation of all the pelvic and perineal viscera and the abdominal viscera supplied by the inferior mesenteric artery.3 The pelvic splanchnic nerves arise from the ventral rami of the second, third, and fourth sacral nerves as they emerge from the pelvic sacral foramina. The third sacral nerve usually provides the largest contribution; three to ten strands of nerves pass forward and become incorporated into the inferior hypogastric plexus.3 The fibers synapse in the ganglia of the inferior hypogastric plexus and ganglia in the muscular walls of the pelvic viscera.4

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Responses

  • barbara
    What branches off the celiac trunk?
    7 years ago
  • Natsnet
    How far is the celiac trunk from the descending aorta?
    6 years ago

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