Handa 9781496386441 Full Sample Chap 1

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SECTION I  Preparing for Surgery

I ligament with overlying muscle contributes to the pos- terior and inferior boundary of the pararectal space. As its name implies, the sacrospinous ligament courses from the lateral aspect of the sacrum to the ischial spine. In its medial portion, it fuses with the sacrotuberous ligament and is a distinct structure only laterally. It can be reached from the rectovaginal space by perforation of the rectal pillar to enter the pararectal space or by dissection directly under the enterocele peritoneum. It can also be reached from the paravesical space. The nerve to the coccygeus and the levator ani nerve, both from S3–S5, are associated with the anterior surface of muscle–ligament complex. This area is covered in more detail in Chapter 37. Many structures are near the sacrospinous ligament, and their location must be remembered during surgery in this region. The sacral plexus lies cephalad to the ligament on the inner surface of the piriformis muscle, and its major branch, the sciatic nerve, leaves the pelvis through the lower part of the greater sciatic foramen. The sacral plexus supplies nerves to the muscles of the hip, pelvic diaphragm, and perineum, as well as to the lower leg (through the sciatic nerve). Just before it exits through the greater sciatic foramen, the sacral plexus gives off the pudendal nerve, which, with its accompa- nying vessels, passes posterior to the sacrospinous liga- ment close to the ischial spine. The nerve to the levator ani muscles, which arises from S3–S5 fibers, passes over the midportion of the coccygeus muscle to supply the levator muscles. The nerve to the coccygeus muscles also arises from S3–S5 nerves and perforates this mus- cle from its pelvic surface. In developing this space, the tissues that are reflected medially and cranially to gain access contain the pelvic venous plexus of the internal iliac vein, as well as the middle rectal vessels. If they are mobilized too vigorously, they can cause considerable hemorrhage. The internal pudendal and inferior gluteal vessels and the third sacral nerve and pudendal nerve are associated with the superior margin of the sacrospinous ligament and can be injured if the exit or entry point of a needle extends above the upper extent of the ligament. The internal pudendal artery passes behind the lateral third of the ligament, and the inferior gluteal exits the greater sciatic foramen at the mid ligament level, usually by passing between the second and third sacral nerves. The third sacral nerve and pudendal nerve course just above and almost parallel to the upper margin of the ligament. The small fourth sacral nerve passes over the medial surface of the ligament to join the third sacral nerve in forming the pudendal nerve (see FIG. 1.15 ). RETROPERITONEAL SPACES AND LATERAL PELVIC WALL The retroperitoneal space contains the major neu- ral, vascular, and lymphatic supply to the pelvic vis- cera. This space may be explored during operations

to identify the ureter, interrupt the pelvic nerve supply, arrest serious pelvic hemorrhage, and remove poten- tially malignant lymph nodes. Because this area is gen- erally free of the adhesions from serious pelvic infection or endometriosis, it can be used as a plane of dissec- tion when the peritoneal cavity has become obliterated. The structures found in these spaces are discussed in a regional context, because that is the way they are usu- ally approached in the operating room. Retroperitoneal Structures above the Pelvic Brim The abdominal aorta lies on the lumbar vertebrae slightly to the left of the vena cava, which it partially overlies. The renal blood vessels arise at the second lumbar vertebral level. The left renal vein passes on the anterior surface of abdominal aorta, just below the supe- rior mesenteric artery. Below the renal vessels, the aorta and vena cava are encountered during retroperitoneal dissection of the para-aortic lymph nodes ( FIG. 1.33 ). The ovarian vessels also arise from the anterior surface of the aorta in this region, just below the renal ves- sels. In general, the branches of the vena cava follow those of the aorta, except for the vessels of the intestine, which flow into the portal vein, and the left ovarian vein, which empties into the renal vein on that side. The inferior mesenteric artery arises from the ante- rior aorta below the level of the renal vessels and just below the third portion of the duodenum, approxi- mately at the third lumbar vertebral level. It supplies the distal third of the transverse colon, descending colon, sigmoid colon, and rectum. It gives off ascending branches of the left colic artery and continues caudally to supply the sigmoid through the three or four sigmoid arteries that lie in the sigmoid mesentery. These vessels follow the bowel as it is pulled from side to side, so that their position can vary, depending on retraction. The superior rectal artery is the terminal continua- tion of the inferior mesenteric artery. This vessel crosses over the left external iliac vessels to lie on the dorsum of the lower sigmoid. It supplies the rectum, as described in the section concerning that viscus. The aorta and vena cava have segmental branches that arise at each lumbar level and are called the lumbar arteries and veins. They are situated somewhat posteri- orly to the aorta and vena cava and are not visible from the front. When the vessels are mobilized, as is done in excising the lymphatic tissue in this area, they come into view. At the level of the fourth lumbar vertebra, just below the umbilicus, the aorta bifurcates into the left and right common iliac arteries. After about 5 cm and approxi- mately at the level of the sacroiliac joint, the common iliac arteries (and the medially and posteriorly placed veins) give off the internal iliac vessels from their medial side and continue toward the inguinal ligament as the

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