Surgical Anatomy of the Retroperitoneal and Pelvic Extraperitoneal Space

Chapter

Abstract

The retroperitoneal space (retroperitoneum) is a potential space in the posterior peritoneal cavity that lies between the parietal peritoneum internally and the fascia of posterior abdominal wall externally. The space extends from the diaphragm superiorly to the sacral promontory and to the arcuate line inferiorly, which communicates with the pelvic extraperitoneal space inferiorly, with mediastinal connective tissue superiorly through the lumbocostal triangles, as well as with extraperitoneal fat bilaterally. Therefore, a primary tumor located in the retroperitoneal space may spread or invade to the posterior mediastinum, lateral abdominal wall, or pelvic extraperitoneal space. The retroperitoneal space can be divided into left lumbar region (left flank), right lumbar region (right flank), prevertebral region, left iliac fossa (RIF), and right iliac fossa (LIF) areas.

1 Surgical Anatomy of the Retroperitoneal Space

1.1 Overview

The retroperitoneal space (retroperitoneum) is a potential space in the posterior peritoneal cavity that lies between the parietal peritoneum internally and the fascia of posterior abdominal wall externally. The space extends from the diaphragm superiorly to the sacral promontory and to the arcuate line inferiorly, which communicates with the pelvic extraperitoneal space inferiorly, with mediastinal connective tissue superiorly through the lumbocostal triangles, as well as with extraperitoneal fat bilaterally. Therefore, a primary tumor located in the retroperitoneal space may spread or invade to the posterior mediastinum, lateral abdominal wall, or pelvic extraperitoneal space. The retroperitoneal space can be divided into left lumbar region (left flank), right lumbar region (right flank), prevertebral region, left iliac fossa (RIF), and right iliac fossa (LIF) areas.

The flank is the surrounding area that originates from the level of the 12th thoracic vertebrae and the 12th rib and extends downward to the sacral promontory and iliac crest. The left flank is continuous with the right flank through the prevertebral area. The longitudinal groove located at the outer edge of erector spinae marks its exterior boundary. When viewing from the abdominal cavity, the exterior edge of the quadratus lumborum defines its exterior boundary. Retroperitoneal tumors usually can extend beyond the abovementioned exterior boundaries or cause displacement of quadratus lumborum by pushing them outward. The base of the flank and iliac fossa is formed by the quadratus lumborum and psoas major whose surfaces are covered by fascia. The psoas major is connected downward to the iliac fascia and thus constitutes the posterior wall of retroperitoneal space (Serio and Tenchini 1998).

The retroperitoneal space contains abundant loose connective tissue and adipose tissue. Retroperitoneal tissue is divided into three layers: (a) outer layer of transversalis fascia, close to the inner surface of the posterior abdominal muscles; (b) inner layer, peritoneal basement membrane, constructed by an inner connective tissue layer located directly at the deeper peritoneal surface; and (c) middle layer positioned between the abovementioned two layers. Its thickness varies with the individual’s body weight as well as its surrounding organs or structures. Retroperitoneal tissue either fills in the space between the muscle and organs, such as the duodenum, ascending colon, and descending colon, or encapsulates the kidney, renal vessels, ureter, abdominal aorta, inferior vena cava, iliac artery, lumbar sympathetic trunk, lymph nodes, etc. The organs and urinary system in the retroperitoneal space are shown in Fig. 1.1. As retroperitoneal tumors may involve the abovementioned structures, the surgical treatment of these tumors becomes extremely complex (Nishino et al. 2003).
Fig. 1.1

Front view of the organs and the urinary system in the retroperitoneal space

1.2 Kidney

1.2.1 Shape and Location of Kidney

Kidneys are horse bean-shaped organs located on both sides of the spine. Each of them has anterior vs. posterior surfaces, upper vs. lower poles, and lateral vs. medial borders. The upper pole of the kidney is wide and thin, while the lower pole is narrow and thick. The kidneys lie in the superior part of the retroperitoneum on either side of the spine with upper poles slightly tilted toward the spine. The superior pole of the right kidney is adjacent to the liver, typically making it lower in position than the left kidney. The left kidney therefore lies at a position approximately between vertebral levels T11-L2, whereas the right kidney occupies an area approximately between vertebral levels T12-L3. Kidneys move with respiratory movements of the diaphragm within the range of no more than one vertebra (Rohen et al. 1998).

The renal outer edge is convex, whereas the inner edge is concave. The renal hilus is located in the center of the concave area, serving as the point of entry and exit of the renal vein and artery, renal pelvis, nerves, and lymphatic vessels. The structures at the renal hilus of the kidney from the front backward are the renal vein, renal artery, and renal pelvis and from above downward are the renal artery, renal vein, and renal pelvis. All structures that pass through the renal hilus are enclosed in connective tissues, forming the renal pedicle.

1.2.2 Anatomic Relationships

The upper one third of the anterior left kidney is related to the stomach, the middle one third is adjacent to jejunum, the upper lateral half is in contact with the spleen, and the lower lateral half is adjacent to colic flexure. The upper two thirds of the anterior right kidney is close to the right lobe of the liver, and the lower one third part is in relation to the hepatic flexure of the colon. A narrow area along the curved medial border is in contact with the descending part of the duodenum. The upper pole is separated from suprarenal gland by adipose tissue. Posteriorly, the parts of kidneys above the 12th rib are close to the diaphragm, whereas below the 12th rib they are close to the psoas major, quadratus lumborum, and transversus abdominis, as well as subcostal, iliohypogastric, and ilioinguinal nerves that run downward.

1.2.3 Capsules of the Kidneys

The coverings of the kidneys from outer inward consist of three layers, renal fascia, adipose capsule, and fibrous capsule. The renal fascia is comprised of peritoneal connective tissue and divided into an anterior and a posterior layer, which enclose the kidney and the suprarenal gland along with the anterior of their vessels and adipose capsule. Medially the anterior layer of the fascia is continuous with the contralateral renal fascia across the abdominal aorta and the inferior vena cava. The posterior renal fascia is firmly attached to posterior kidney and the link between the psoas major and quadratus lumborum and medially attached to the side of lumbar vertebrae and intervertebral disks. The anterior and posterior layers of the renal fascia fuse and unite with the fascia of diaphragm above the suprarenal gland but remain separate below it. The posterior renal fascia extends to the lumbar fascia, and the anterior layer encloses the ureter and continues to the pelvis. Perirenal adipose capsule is comprised of adipose tissue, which envelopes both the kidney and suprarenal gland. Especially for the obese, a huge amount of adipose capsule develops, acting as a protective buffer against pressure. There is a very tiny amount or no fatty tissue in front of the kidney, while the renal margin is relatively thicker and enters into the renal sinus. The adipose capsule allows X-ray to pass through, which is in sharp contrast to the renal parenchyma, making it ideally suitable for imaging. The fibrous capsule is an intrinsic renal capsule, enclosing the surface of the renal parenchyma. It is thin, firm, and tenacious, consisting of dense connective tissue and a few elastic fibers. When the fibrous capsule is invaded by retroperitoneal tumors, resection of the renal parenchyma is highly recommended. After partial kidney removal, this layer should be sutured.

1.2.4 Renal Vasculature (Artery and Vein), Lymphatic Vessel, and Nerve

Each kidney weighs about 120–150 g, with a relatively thick and large renal artery and vein. The renal arteries normally arise off the side of the abdominal aorta. The most common location for the origin of renal artery was the L1-L2 intervertebral disk level. The right renal artery is normally longer than the left one. An average diameter of renal arteries is 0.77 cm. The renal artery extends exteriorly and ramifies in the renal hilus into the anterior and posterior branches. Most of people have one renal artery originally for each kidney (86%); a minority gives off two branches, occasionally up to three or four branches.

Accessory renal arteries are common; variate is present in 41.8% of Chinese. They enter into the kidneys through the upper or lower pole instead of passing through the renal hilum. The most common types of origins of the accessory renal arteries in Chinese patients are (A) from the renal artery, (B) from a renal artery segment, (C) from the abdominal aorta, and (D) sharing a branch with adrenal artery. Types A and B are most common, followed by type C. When a resection of kidney is required due to invasion of a retroperitoneal tumor, close attention should be paid to the above anatomical variations.

Renal veins are located inside of the renal hilum and typically merge into one large trunk by 2–3 branches running gradually inward. Renal veins run in front of their corresponding arteries and finally join the inferior vena cava at an approximate right angle. The left renal vein is normally 2 or even more than 3 times longer than the right vein. Besides collecting the left renal vein blood, the left renal vein also houses blood from the left suprarenal gland and testicles (ovaries). Therefore, after being invaded by retroperitoneal tumors, left renal vein can reversely drain through testicular (ovarian) vein. Our team previously established one case of renal vein—left ovarian vein anastomosis to preserve the left kidney function in our hospital. Branches of the left renal vein occasionally anastomose with veins of posterior abdominal wall, and more than half of left renal veins have a large branch which coincides with the ascending lumbar vein. During surgery, it should be noted that in this case, the vertebral venous plexus can be connected to the left renal vein through special communications.

Four to five large lymphatic vessels are formed by confluence of renal lymphatic vessels around the renal pedicle, entering into lumbar lymph nodes and lumbar trunk. The constriction of left renal vein by enlarged retroperitoneal lymph nodes may result in testicular varicose veins. Similarly, lymphatic vessels around renal pedicle can become thickened, distorted, or even destroyed due to the compression and obstruction of cisterna chyli or thoracic duct, leading to chyluria.

The kidney plexus is formed by branches from the celiac plexus around the renal artery. Abdominal aortic plexus and branches of lumbar sympathetic trunk are also distributed along the branches of the renal artery. Tumors of neurogenic origin can occur in these areas.

1.3 Suprarenal Gland

The suprarenal gland is one of the most important endocrine organs in the human body. They are connected with the upper poles and anteromedial sides of both kidneys and enclosed by renal fascia and adipose capsule. The right adrenal gland is pyramidal in shape, attaching to the anteromedial side of the upper pole of the right kidney on the recessed bottom surface. The anterior part of adrenal gland is divided by the longitudinal ridge into an inner region which is not covered by peritoneum at the inner side and directly attached to the back of the inferior vena cava and an outer region which is adjacent to the right lobe of liver and the superior part of duodenum. If the suprarenal gland that is posteriorly attached to the diaphragm is at a higher location, visceral nerves pass through between them and join the celiac plexus. The medial margin is convex, adjacent to right celiac ganglion and right inferior phrenic artery. The left suprarenal gland is shaped like a half moon, closely attached to the superior medial side of the left kidney on the recessed bottom surface, connecting to the renal vessels. The anterior aspect of suprarenal gland is adjacent to the posterior wall of stomach superiorly and connected to the splenic artery and vein as well as the pancreas inferiorly. Also, the left splanchnic nerve passes between the posterior aspect of the suprarenal gland and the diaphragm.

The normal size of the suprarenal gland is about 5 cm in length, 3 cm in width, 0.5–1 cm in thickness, and 5–7 g in weight. Suprarenal glands do not move with nephroptosis and have rich blood supply. There are upper, middle, and lower arteries on each side of the suprarenal gland, stemming from the inferior phrenic artery, abdominal artery, and renal arteries, respectively. The origins of these arteries have also been reported as accessory renal artery, gonadal artery, abdominal artery, ureter artery, superior mesenteric artery, renal adipose capsule artery, and common hepatic artery. Each suprarenal gland lack one of the three arteries. Most often each suprarenal vein has only one branch. The left suprarenal vein receives blood from the left inferior phrenic vein on the medial side of the suprarenal glands, descends inwardly, and passes at an acute angle into the upper margin of the left renal vein. The right adrenal vein descends inwardly and mostly flows into the right posterior wall of the inferior vena cava. Otherwise it can enter into the right accessory hepatic vein, etc. Retroperitoneal tumors may displace suprarenal glands, resulting in physical changes in the above blood vessels. For patients with tumors infiltrating the suprarenal gland(s), the resection should be performed by experienced surgeons who are very familiar with retroperitoneal vascular anatomy in order to avoid intraoperative bleeding or accidental damage to inferior vena cava and other important structures.

Neural tumors, pheochromocytomas, may occur in suprarenal gland medulla that is composed of sympathetic ganglion cells (pheochromocytes). Although beyond the scope of retroperitoneal tumors, they are similar in pathogenesis to extra-adrenal pheochromocytomas (also called paragangliomas) which may be derived from peritoneal sympathetic postganglionic neurons with the same functions as medulla cells.

1.4 Ureter

Ureters are a pair of elongated muscular tubes located in the retroperitoneal space, arising from the pelvis of each kidney superiorly and opening into the bladder inferiorly. In adults, the ureter is 25–30 cm in length and 4–7 mm in diameter. The ureter consists of an abdominal part, a pelvic part, and an intramural part. The abdominal part of ureter descends along the anterior of the psoas major, gradually deviates toward the midline, and goes downwardly to the superior aperture of the small pelvis where the left ureter passes in front of the left common iliac artery; the right ureter passes through in front of the right external iliac artery into the pelvic extraperitoneum. The ureter crosses over the testicular blood vessels in men (ovarian blood vessels in women) slightly below the midpoint of the psoas major, where blood vessels descend in front of the ureter. The anterior of the abdominal part of the left ureter is adjacent to duodenojejunal flexure, the left colonic vessels, and sigmoid colon from up to down. The abdominal part of the right ureter is next to the descending part of duodenum, the root of the small bowel mesentery, and appendix. Clinically, retroperitoneal tumors frequently compress, distort, and even invade ureter(s), eventually leading to obstruction.

The ureteral blood supply is derived from multiple sources. The abdominal origins of arterial blood supply to the ureter include small branches of the abdominal aorta, renal artery, testicular (or ovarian) arteries, and iliac arteries. After reaching the surface of the ureter, the arteries bifurcate into ascending and descending branches, which travel along the ureteral walls upward and downward, respectively, anastomose with each other, and further bifurcate into subbranches to supply the ureteral walls. Ureteral veins travel in parallel to the arteries. During surgery, the ureter should not be dissected excessively from retroperitoneal tumors in order to avoid postoperative ureteral ischemia and necrosis.

The ureteral nerves are derived from the renal plexus, abdominal aortic plexus, and hypogastric plexus, which are distributed in the wall of the ureter and constitute ureteric plexus.

When retroperitoneal tumors invade into the ureter, ureteral resection and anastomosis are often performed. Since the ureter is an elongated fibromuscular tube, the anastomosis should be undertaken at a certain inclination angle to maximize the anastomosis surface of the ureter margin and extend the luminal constriction ring, thereby facilitating ureteral patency. Otherwise, patients are prone to develop scars and consequent stenosis, even obstruction.

1.5 Abdominal Aorta

The abdominal aorta is the segment between the left and right common iliac arteries that are derived from thoracic aorta passing through the aortic hiatus of the diaphragm (equivalent to the inferior margin plane of 12th thoracic vertebrae to the 4th lumbar plane). It is located in left-front of the spine, which on average is 13.4 cm in length.

The abdominal aorta runs parallel to inferior vena cava on its right-hand side and parallel to the left sympathetic trunk on its left-hand side. The splenic vein, pancreas, left renal vein, horizontal part of the duodenum, and root of the small bowel mesentery lie from top to bottom in front of the abdominal aorta. Additionally, the lower end of the thoracic duct is situated on the right side or the rear of the initial segment of the abdominal aorta, while the celiac plexus and celiac ganglia are located anterior to this segment. The abdominal aorta is surrounded by the aortic plexus inferiorly. Lumbar lymph nodes lie posterior and lateral to the abdominal aorta.

The abdominal aorta can be divided into four branches: (a) unpaired visceral, (b) paired visceral, (c) parietal, and (d) terminal (Fig. 1.2).
Fig. 1.2

Abdominal aorta and its branches

Unpaired visceral branches include the celiac and superior and inferior mesenteric arteries. The celiac trunk is also known as celiac artery, which arises from the anterior aortic wall, just below the aortic hiatus of the diaphragm. It consists of three large branches, the left gastric, the hepatic, and the splenic. Symptoms may appear at the early stage of retroperitoneal tumors involving the celiac artery due to the vital roles of the organs to which celiac arteries provide blood supply. If the tumor does not grow very large at the time of surgery, it is not hard to remove. The superior mesenteric arteries originate from the anterior wall of the abdominal aorta on the first lumbar vertebra plane, traveling into the small mesenteric root in front of the horizontal part of duodenum through the posterior pancreas and obliquely descending to the vicinity of the right iliac fossa. Tumors originating from this arterial trunk (strictly speaking, they belong to retroperitoneal tumors) usually involve blood vessels as they are located in the mesenteric roots. The author’s team has treated many cases of this type of retroperitoneal tumors with end-to-end anastomoses after resection of these arteries, as well as the distal end of the superior mesenteric artery with inferior mesenteric artery, abdominal aorta, or other vasculature anastomoses to reconstruct the blood supply for the digestive tract and successfully resect the tumor. The inferior mesenteric artery arises from the anterior wall of abdominal aorta at the level of the third lumbar vertebra, descending via the left retroperitoneum to the root of the sigmoid mesocolon and extending to the superior rectal artery in the pelvic cavity. If the inferior mesenteric artery is infiltrated by retroperitoneal tumors, its trunk may be resected, and the intestinal blood flow can be maintained through the plexus that communicates between the mesenteric vessels.

Paired visceral branches include the middle suprarenal, renal, and testicular arteries. The middle suprarenal artery originates from the abdominal aortic sidewall on the first lumbar vertebra plane. The anatomy of renal artery was described above. The testicular artery (ovarian artery in women) arises from the anterior wall of the abdominal aorta immediately below the renal artery, obliquely running outward along the anterior psoas major, descending across the anterior ureter, and giving off branches to the ureter. Outwardly passing through the inner ring into the spermatic cord, it is called the internal spermatic artery. The ovarian artery passes across the bifurcation of common iliac artery or initial segment of external iliac artery into the pelvic cavity where it is distributed to the ovaries and ampulla of the fallopian tube. The testicular artery (ovarian artery) may be resected unilaterally when it is invaded by retroperitoneal tumors.

Parietal branches of abdominal aorta include inferior phrenic artery and lumbar artery. The inferior phrenic arteries most often originate from the abdominal aorta and are located on the side of abdominal aorta on T12–L1 plane. Arteries are 2–2.1 mm in diameter. Additionally, the inferior phrenic artery may also arise from celiac artery, renal artery or accessory renal artery, hepatic artery or accessory hepatic artery, left gastric artery, suprarenal artery, internal spermatic artery, etc. During the resection of retroperitoneal tumors combined with multiple organs, care should be taken to avoid accidental injury to these arteries. If ligation of renal artery or left gastric artery is required, the surgeons should carefully check for the presence of an inferior phrenic artery and perform the ligation and resection as close to the organs as possible in order to ensure a plentiful blood supply to the diaphragm afterward.

The lumbar artery is a major source of blood supply to the posterior abdominal wall and peritoneum. It is mostly composed of four pairs of branches, arising from the posterior and lateral wall of abdominal aorta on the plane between L1 and L1~2, between L2 and L2~3, and between L3 and L4, respectively. Sometimes, a fifth pair of lumbar arteries is derived from the lateral wall of the median sacral artery. The above four pairs of lumbar arteries travel through the deep surface of lumbar sympathetic trunk, cross the tendinous arch over the psoas major to the area between psoas major and spine, and thus are located behind psoas major and lumbar plexus. The first and second pairs of lumbar arteries also pass through the diaphragmatic crura or its posterior surface. The first, second, and third pairs of lumbar arteries cross over the posterior of quadratus lumborum. The right lumbar artery passes posterior of the inferior vena cava to the area between the psoas major and spine. The first and second pairs of the right lumbar arteries also cross over the posterior of cisterna chyli. As the prominent feeding vessels for retroperitoneal tumors mostly arise from lumbar arteries, angiography usually reveals that lumbar arteries have become thickened, stretched, twisted, or ruptured, etc. and given off branches to feed the tumors. Lumbar artery embolization may be performed in such cases. Lumbar arteries should be carefully identified during ligation to avoid uncontrollable bleeding.

Terminal branches of the abdominal aorta include median sacral artery, common iliac artery, and its branches. The median sacral artery is a small terminal branch of the abdominal aorta. It is relegated to the posterior and anterior surface 5 mm above the bifurcation of the aorta after gradually giving way to the iliac artery during human evolution. The median sacral artery descends anterior to the L4~5 vertebrae, sacrum, and coccyx and eventually terminates at coccygeal body. Special care should be taken to avoid any damage to these vessels during presacral (or retrorectal) tumor resection because the superior hypogastric plexus of the left common iliac vein and the sympathetic nerve passes through in front of the median sacral artery. The lowest lumbar artery arises from the lateral wall of median sacral artery; it gives off branches through the posterolateral common iliac artery to the lateral sacrum on both sides, which eventually terminates in the iliac muscle and coincides with the branches of iliolumbar artery. The median sacral artery also gives off four pairs of branches (lateral sacral, rectal, etc.), which should be carefully identified during surgery.

The common iliac artery and its branches are critical for surgical oncology of retroperitoneal tumors. The left and right common iliac arteries originate from the plane of the middle portion of L4 vertebral body and the superior portion of L5 vertebral body. These arteries travel separately to the margin of small pelvis and bifurcate into the internal iliac artery and external iliac artery on the plane between the middle one third of L4 and the superior one third of S1. The internal iliac artery descends into the pelvis and gives off the anterior branch and posterior branch on the plane between the inferior L5 and superior S4. The external iliac artery runs along the margin of the pelvis to the deep surface of inguinal ligament, extending into the femoral artery. The iliac artery is 10.3–10.4 mm in diameter and 4.3–4.6 cm in length. The vessel wall is thinner at the bifurcation of terminal common iliac artery where it divides into internal and external iliac artery, so special care should be taken to avoid any damage when separating from retroperitoneal tumors.

The superior hypogastric plexus passes inward near the front of the right common iliac artery, while the right ureter crosses over the terminal portion of the lateral right common iliac artery or external iliac artery. In addition, the terminal ileum is located anterior, while L4 and L5 lumbar vertebrae body and intervertebral disk are immediately adjacent to the posterior of right common iliac artery. The superior posterior portion of the right common iliac artery is located near the terminus of the left and right common iliac veins at the origin of inferior vena cava and the right sympathetic trunk. Laterally, right common iliac artery is connected to the origin of inferior vena cava and the right common iliac vein superiorly and to psoas major inferiorly. The right common iliac artery is surrounded by iliac lymph node groups outwardly, inwardly, and posteriorly. The anatomical relations of the left common iliac artery are similar to those of the right common iliac artery, except that the sigmoid colon, mesangial root of sigmoid colon, and superior rectal vessel cross over anterior to the left common iliac artery.

The external iliac artery is a direct extension of common iliac artery and is 10.4–11.8 cm in length and 5.9–6 mm in diameter. It passes along the medial margin of the psoas major and descends laterally to the deep surface of inguinal ligament. When the artery crosses the ligament, it becomes the femoral artery. Retroperitoneal tumors sometimes cause displacement of iliac artery; this anatomical variation should be identified carefully during surgery.

Acute abdominal aortic occlusion at or above the renal artery plane may be fatal, whereas below the plane it frequently leads to lower limb gangrene. Compression of retroperitoneal tumors may contribute to chronic abdominal aortic occlusion, which is not life-threatening. Lumbar sympathectomy performed to dilate small blood vessels of limbs is helpful to prevent and reduce the damage caused by the blockade.

1.6 Inferior Vena Cava

Inferior vena cava is formed by the merger of the left and right common iliac veins on the plane between L4 and L5 lumbar vertebrae. It ascends along the right side of the abdominal aorta behind the liver, is enclosed by the vena cava tube, and eventually passes through the central tendon of diaphragm on the right side into the thoracic cavity. The total length of the inferior vena cava is 25.7–27.1 cm, and its diameter is 2.6–3.4 cm. From top to bottom, the right lobe of the liver, the medial margin of the right kidney, and the descending part of duodenum are located on the right side, while the caudate lobe, right crus of diaphragm, and abdominal aorta are located on the left side; the right crus of the diaphragm, right kidney and right suprarenal gland, vertebrae and anterior longitudinal ligament, right psoas major, and right sympathetic trunk are located posteriorly; and common iliac arteries, mesenteric root, right internal spermatic vessels, and sometimes right colonic blood vessels are located anteriorly.

Branches of the inferior vena cava include the renal vein, common iliac vein, internal iliac vein, external iliac vein, etc., which travel parallel to their corresponding arteries (Fig. 1.3). The veins are located on or above the plane of renal vein and cannot adapt to sudden complete occlusion of inferior vena cava, so ligation cannot be performed in this area. In contrast, when the ligation of inferior vena cava is performed below the plane of renal vein, collateral circulation can be established as follows: (a) through the femoral vein, inferior epigastric vein, and superior epigastric vein to the subclavian vein; (b) through the deep circumflex iliac vein, ascending lumbar vein, azygos vein, or semi-azygos vein to the superior vena cava; (c) through the internal iliac vein and inferior mesenteric vein to the portal vein; (d) through the common iliac vein, internal iliac vein, and ascending lumbar vein to the internal and external vertebral venous plexus, which is the major collateral circulation after occlusion of the inferior vena cava; and (e) superficial branches, mainly from the femoral vein through superficial epigastric vein, the thoracoepigastric vein, and the lateral thoracic vein to the superior vena cava system. The presence of these collateral circulations lays a theoretical foundation for treatment of inferior vena cava occlusion caused by invasion of retroperitoneal tumors.
Fig. 1.3

Inferior vena cava and its branches

1.7 Retroperitoneal Lymph Nodes and Lymphatic Vessels

Lymph nodes and lymphatic vessels in retroperitoneal space (Fig. 1.4) are located around the major retroperitoneal blood vessels. They mainly collect the lymph from the lower extremity, pelvis, abdomen, and retroperitoneal organs and drain into the abdominal segment of thoracic duct. They consist of the external iliac, common iliac, and lumbar lymph nodes. External iliac lymph nodes are located medial, lateral, anterior, and posterior to the external iliac vessels, extending upward to the common iliac lymph nodes arranged along the common iliac vessels. Lumbar lymph nodes are distributed around the abdominal aorta and inferior vena cava. Nodular masses formed by confluence of the nodules around these vessels often result from retroperitoneal lymphomas.
Fig. 1.4

Retroperitoneal lymph nodes and lymphatic vessels (green)

The cisterna chyli usually lies in front of the first and second lumbar vertebrae, between right phrenic angle and abdominal aorta, sometimes up to the level of the eleventh thoracic vertebra. It looks like a triangular or spindle-shaped capsule and is 3–4 cm long. It collects the lymph from the left and right lumbar trunks and intestinal trunks (formed by confluence of abdominal lymph nodes, superior mesenteric lymph nodes, and inferior mesenteric lymph nodes). The cisterna chyli ascends through the aortic hiatus into chest, extending to the thoracic duct (Harisinghani et al. 1999).

1.8 Lumbar Sympathetic Trunk and Celiac Plexus

1.8.1 Lumbar Sympathetic Trunk

The lumbar sympathetic trunk (Fig. 1.5) consists of 4–5 lumbar sympathetic ganglia and communicating branches between them. Bilaterally, it is located in front of the lumbar spine and the medial margin of the psoas major. The lumbar sympathetic trunk is covered by the inferior vena cava on the right side and descends along the abdominal aorta on the left side. The lumbar sympathetic trunks on both sides are connected via transverse fibers posterior to abdominal aorta and inferior vena cava. Upwardly, they are connected to the thoracic portion of sympathetic trunk via interganglionic branches. Downwardly, they are connected to the sacral sympathetic trunk via interganglionic branches along the posterior common iliac vessel. Branches of the lumbar sympathetic trunk include:
  1. a.

    Gray ramus communicans, which rejoins five pairs of anterior branches of lumbar nerves. Its fibers are distributed not only in sweat glands, small blood vessels, and arrector pili of the skin along with lumbar nerves but also in the lower limbs along with blood vessels.

     
  2. b.

    The lumbar splanchnic nerve, which contains preganglionic fibers passing through the lumbar sympathetic ganglia, while postganglionic fibers are distributed in the digestive tract and pelvic organs below the left colic flexure.

     
Fig. 1.5

Retroperitoneal autonomic ganglia and nerve plexuses

1.8.2 Autonomic Nerve Plexuses

Autonomic nerve plexuses including the celiac plexus are located around the celiac trunk and the root of superior mesenteric artery and between the two kidneys. The greater or lesser splanchnic nerve, upper ganglia of lumbar sympathetic trunk, bilateral vagus nerves, and bilateral branches of phrenic nerve are included in the celiac plexus, which gives off many branches joining the phrenic plexus, liver plexus, stomach plexus, spleen plexus, renal plexus, superior mesenteric plexus, inferior mesenteric plexus, suprarenal plexus, and spermatic plexus. These plexuses travel parallel to corresponding arteries and are distributed to various organs.

2 Anatomy of Pelvis

2.1 Pelvis

The bony pelvis (Fig.1.6), a skeletal ring, is formed by sacrum and coccyx connecting to bilateral hip bones, as a protective barrier for pelvic organs. The arcuate line of sacral promontory and ilium, iliopubic eminence, pecten pubis, pubic tubercle, pubic crest, and superior margin of pubic symphysis make up a ring line by which the pelvis is divided into a small inferior portion called the true (minor) pelvis and a large superior one called the false (major) pelvis. The anterior wall of the pelvic cavity consists of bilateral pubic portions of the pubic symphysis. The posterior wall is constituted by sacrum and coccyx, and the lateral wall is composed of the ilium, ischium, sacral spine ligament, and sacrotuberous ligament. The greater sciatic foramen is formed by the sacrospinous ligament and sacrotuberous ligament, anterolaterally bounded by the greater sciatic notch. The lesser sciatic foramen is formed by the sacrospinous ligament and sacrotuberous ligament, defined by the boundaries of lesser sciatic notch and the two ligaments. The greater sciatic foramen is a communication between pelvis and hip, while the lesser sciatic foramen is a communication between the hip and perineum. Blood vessels and nerves pass through these foramina. The obturator canal is located in the obturator foramen at the junction of ilium, pubis, and ischium in the front of sciatic foramen, acting as a communication bridge between the pelvis and the medial portion of femora, where the obturator nerve and vessels pass through. As extraperitoneal tumors that occur in pelvis sometimes pass through sciatic foramen, obturator, etc., familiarity with the anatomy is very important for accurate interpretation of the clinical presentation and for the development of efficient therapeutic strategies.
Fig. 1.6

Anatomy of male pelvic extraperitoneum

2.2 Muscles of Pelvic Wall and Pelvic Diaphragm

2.2.1 Internal Obturator Muscle

Internal obturator muscle is a pelvic wall muscle arising from the basal surface of the obturator membrane and the surrounding bone surface, posteriorly crossing the lesser sciatic foramen to the hip and terminating in the trochanteric fossa of the femur outwardly between piriformis and quadratus femoris. The obturator on the upper margin of the muscle is not completely closed; instead, it forms an obturator canal through which tumors in the pelvis may penetrate.

2.2.2 The Piriformis Muscle

The piriformis muscle is a pelvic wall muscle arising from the basal surface of sacrum, laterally crossing through the greater sciatic foramen to the hip, terminating at the tip of the greater trochanter. The piriformis laterally rotates the femur with hip extension and abducts the femur with hip flexion.

2.2.3 The Levator Ani Muscle

The levator ani muscle is a muscle of the pelvic diaphragm which can be divided into four parts according their attachment sites:
  1. a.

    The pubic vaginal muscle (puboprostatic muscle), originating from the basal surface of the pubis and the anterior part of tendinous arch of the levator ani muscle, traveling posteriorly bilaterally along the urethra and vagina, attaching to the muscular layer in the urethral and vaginal wall (it bypasses the prostate and terminates in the perineal central tendon in men).

     
  2. b.

    Puborectalis, which commences in the anterior part of tendinous arch of levator ani muscle and the basal surface of medial part of pubis and posteriorly terminates on the lateral and posterior walls of anal canal as well as the central tendon of perineum. It constitutes a “U”-shaped half a circle with their contralateral counterparts.

     
  3. c.

    The pubococcygeus has the same origin as the puborectalis and terminates at the tip of the coccyx and its lateral margin and anococcygeal ligament.

     
  4. d.

    The musculus iliococcygeus which originates from the posterior part of tendinous arch of the levator ani muscle and the basal surface of ischial spine and terminates posteromedially at the lateral margin of coccyx and anococcygeal ligament.

     

2.2.4 The Coccygeal Muscle

The coccygeal muscle is a muscle of the pelvic diaphragm located in the posterolateral musculus iliococcygeus, mostly originating from the ischial spine posteromedially and terminating in the flank of sacrum and coccyx.

It is not uncommon that extraperitoneal tumors invade the muscles of the pelvic wall and pelvic diaphragm. During surgical resection the involved muscles should be dissected carefully, otherwise residual tumor tissues may develop local recurrence and distant metastases.

2.3 Rectum and Anal Canal

The rectum and anal canal are the terminal parts of digestive tract, posteriorly adjacent to fascia in front of sacrum and coccyx, through which the sacral plexus, pelvic splanchnic nerves, pelvic sympathetic trunk, and superior rectal veins and arteries pass. This is a common area for presacral tumors (e.g., teratoma, etc.) to occur. Bilaterally the rectum is attached to the lateral wall of pelvis through the rectal lateral ligament that encloses the inferior rectal vessels and pelvic splanchnic nerves. The pelvic plexuses and branches of the internal iliac artery are located anteriorly to the ligament. The rectovesical pouch or rectouterine pouch is located anterior to the rectum and superiorly below the peritoneum reflex. The rectum is adjacent to the seminal vesicles, ampulla ductus deferentis, prostate, and ureter in men (adjacent to cervix and vagina in women).

2.4 Bladder

The bladder lies in the extraperitoneum anterior to pelvis, closely attached to the basal surface of pubis. It is filled with loose connective tissue and is where pudendal venous plexus passes through. The bladder is adjacent to the rectum, seminal vesicles, and ampulla ductus deferentis posteriorly in men (to the anterior wall of the vagina and cervix in women). Paravesical tissues are located on both sides of the bladder, through which the arteries and nerves insert into bladder.

The prostate is located posteroinferiorly to the symphysis pubis immediately below the bladder, surrounding the beginning of urethra in the male. The author’s team has conducted total pelvic exenteration for eight cases of pelvic extraperitoneal tumors. Detailed knowledge of the pelvic anatomy plays a vital role in this surgery.

2.5 Blood Vessels, Lymph Nodes, and Nerves in Pelvis

In the previous sections, the trunks of common iliac arteries, external iliac arteries, and internal iliac arteries were described in detail. The pelvic vascular anatomy is shown in Fig. 1.6. The internal iliac artery runs along the posterolateral wall of the pelvis within the pelvic fascia. It is posterior and medial to the ureter, anterior to the lumbosacral trunk, and medial to obturator nerve. While running downward to the upper margin of the piriformis, it divides into two large trunks, anterior and posterior. Branches of anterior trunk include (a) the obturator artery, which travels along the pelvic sidewall forward through the obturator canal to the femoral region and (b) the inferior gluteal artery which exits the pelvis via the infrapiriform foramen to the hip. The anterior trunks also give off the umbilical artery, inferior vesical artery, inferior rectal artery, internal pudendal artery, uterine artery, or deferential artery. After birth, the distal segment of umbilical artery occludes, while the proximal segment remains open and bifurcates into 2–3 superior vesical arteries. The inferior rectal artery enters the lateral ligament, which is posterior to the inferior vesical artery and anterior to the internal pudendal artery. The uterine artery descends forward and medially along the pelvic sidewall to the base of broad ligament of uterus and medially 2 cm from the cervical margin where it intersects with the ureter after crossing over its anterior-superior segment and then wiggles upward along the cervical margin in a tortuous manner. The posterior branches include the iliolumbar artery, lateral sacral artery, and superior gluteal artery: the latter exits the pelvis via the suprapiriform foramen to the hip. Combined resection of the sacrum and retroperitoneal tumors often involves the lateral sacral arteries. The internal iliac vein and its tributaries generally travel in parallel to their corresponding arteries. It should be noted that venous plexuses are always formed when the veins surround the organs in the pelvis, such as exterior anorectal venous plexus, bladder venous plexus, uterine venous plexus, vaginal venous plexus, and genital venous plexus, all of which communicate with one another and eventually confluence into the veins to rejoin the internal iliac vein.

Apart from the abovementioned vessels, the median sacral arteries, superior rectal arteries, and ovarian arteries are also situated in the pelvis, which should be carefully identified during surgical resection of extraperitoneal tumors.

The pelvic lymph nodes are generally arranged along the blood vessels and consist of the common iliac lymph nodes, external iliac lymph nodes, internal iliac lymph nodes, and sacral lymph nodes; the latter is located in front of the sacrum along the median sacral artery.

The pelvic nerves include:

(a) The sacral plexus, located in front of the sacrum and piriformis. It gives off branches that exit the pelvis via the suprapiriform foramen and the infrapiriform foramen of the piriformis. Presacral tumors may compress these nerves leading to pain of lower limbs.

(b) The pelvic sympathetic trunk which extends downwardly from the lumbar sympathetic trunk. The left and the right trunk separately descend along the medial side of the anterior sacral foramen to the anterior surface of coccyx, where they merge. After confluence, the sympathetic trunks give off postganglionic fibers to constitute the pelvic plexuses.

(c) The pelvic splanchnic nerve, also known as pelvic nerve or erectile nerve, belongs to the parasympathetic nerves and is formed by 2–4 fibers from the anterior rami of sacral nerve. It subsequently joins the pelvic plexus.

(d) The superior hypogastric plexus and inferior hypogastric plexus. The superior hypogastric plexus (also known as the anterior sacral nerve) is located anterior to the 5th lumbar spine, between the bilateral common iliac arteries, as a descending extension from abdominal aortic plexus. It gives off the left and the right hypogastric nerves which connect to the left and the right inferior hypogastric plexus (pelvic plexus), respectively. The inferior hypogastric plexus that runs on both sides of the rectum lateral ligament is formed by the intertwining of the hypogastric nerve, pelvic splanchnic nerve, and postganglionic fibers arising from pelvic sympathetic ganglia, etc.

(e) The obturator nerve which arises from the lumbar plexus through the medial border of the psoas major and posterior aspect of the common iliac artery into the pelvic cavity. It travels along the pelvic sidewall lateral to the ureter, superior to its corresponding vessels, and forward through the obturator canal to the femoral region. Tumors on the sidewall of the pelvis that grow into the obturator foramen can compress the obturator nerve and cause pain in hip and lower limbs (Harisinghani et al. 1999).

3 Sectional Anatomy of Abdomen and Pelvis

CT and MRI imaging is a vital tool for diagnosis and therapy of retroperitoneal tumors. Surgeons in the department of retroperitoneal surgical oncology should have a firm grasp on the sectional anatomy and thus be able to interpret the imaging accurately before surgery.

3.1 Cross Section of Retroperitoneal Space

When viewing from the cross section of the first lumbar vertebra (Fig.1.7), the psoas major lies on both sides of the lumbar spine within the intraperitoneal space, medial to renal cross section and posterior to the ureter. Ascending and descending colons are located lateral and anterior to the kidneys.
Fig. 1.7

Cross section of abdomen (L1 level)

On this plane, the abdominal great vessels are situated anterior to lumbar vertebrae. Cross section of the inferior portion of the duodenum can be seen in front of the abdominal aorta (left) and the inferior vena cava (right).

3.2 Cross Section of Extraperitoneal Pelvis

Viewing from the horizontal cross section of urethral sphincter and vagina (Fig. 1.8), sacrum, rectum, and other extraperitoneal organs can be found.
Fig. 1.8

Cross section of pelvis (vaginal and urethral sphincter level)

The normal retroperitoneal and pelvic extraperitoneal spaces are not very distinct on cross section making it difficult to determine their boundaries using CT and MRI images. However, it is necessary to identify whether tumors, especially large tumors present in these spaces, are located in the retroperitoneum (extraperitoneum) or intraperitoneum. In addition, a huge retroperitoneal tumor that expands far beyond the retroperitoneal space can occupy the normal position of the abdominal cavity and abdominal organs. Therefore, comprehensive understanding of the retroperitoneal or extraperitoneal space must be based on the structural anatomy of the abdominal and pelvic cavities, as well as the organs in the abdomen and pelvis.

References

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  2. Nishino M, Hayakawa K, Minami M, Yamamoto A, Ueda H, Takasu K. Primary retroperitoneal neoplasms: CT and MR imaging findings with anatomic and pathologic diagnostic clues. RadioGraphics. 2003;23(1):45–57.Google Scholar
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  4. Serio G, Tenchini P, Nifosi F, Lacono C. Surgical strategy in primary retroperitoneal tumours. Br J Surg. 1989;76(4):385–89.Google Scholar

Copyright information

© Springer Science+Business Media B.V. 2018

Authors and Affiliations

  1. 1.Peking University Health Science CenterBeijingChina
  2. 2.Peking University International HospitalBeijingChina

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