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CHAPTER 1  Surgical Anatomy of the Female Pelvis

voiding and defecation dysfunction are also common following radical pelvic surgeries. How these autonomic nerves reach the organs that they innervate has surgical importance. The terminol- ogy of this area is somewhat confusing, because many authors use idiosyncratic terms. However, the structure is simple: a single ganglionic midline plexus overlies the lower aorta (superior hypogastric plexus). This plexus splits into two trunks without ganglia (hypogastric nerves), each of which connects with a plexus of nerves and ganglia lateral to the pelvic viscera known as the inferior hypogastric plexus ( FIG. 1.35 ). The superior hypogastric plexus lies in the retroper- itoneal connective tissue on the ventral surface of the lower aorta and receives input from the sympathetic chain ganglia through the thoracic and lumbar splanch- nic nerves. It also contains important afferent pain fibers from the pelvic viscera, which makes its tran- section sometimes effective in primary dysmenorrhea. It passes over the bifurcation of the aorta and extends over the proximal sacrum before splitting into two hypogastric nerves that descend into the pelvis toward the region of the internal iliac vessels. On each side of the pelvis, the hypogastric nerves end in the inferior hypogastric plexus. The inferior hypogastric plexuses are broad expan- sions of the hypogastric nerves. Their sympathetic fibers come from the downward extensions of the superior hypogastric plexus and from the sacral splanchnic nerves, a continuation of the sympathetic chain or trunk into the pelvis. Parasympathetic fibers come from sacral segments two through four by way of the parasympathetic root of the pelvic ganglia (pelvic splanchnic nerves). They lie in the pelvic con- nective tissue of the lateral pelvic wall, lateral to the uterus and vagina. The inferior hypogastric plexus (sometimes called the pelvic plexus) is divided into three portions: the vesical plexus, the uterovaginal plexus (Frankenhäuser ganglion), and the middle rectal plexus. The utero- vaginal plexus contains fibers that derive from two sources. It receives sympathetic and sensory fibers from the tenth thoracic through the first lumbar spi- nal cord segments. The second input comes from the second, third, and fourth sacral segments and consists primarily of parasympathetic nerves that reach the inferior hypogastric plexus through the pelvic splanch- nic nerves. The uterovaginal plexus lies on the dorsal and medial surface of the uterine vessels, lateral to the uterosacral (rectouterine) ligaments’ insertion into the uterus. It has continuations cranially along the uterus and caudally along the vagina. These latter extensions contain the fibers that innervate the vestibular bulbs and clitoris and are called the cavernous nerve of the clitoris. These nerves lie in the tissue just lateral to the area where the uterine artery, cardinal ligament,

and midline iliococcygeal raphe. The rectum and peri- toneum form the anterior boundary; the lower lumbar vertebra, sacrum, and overlying anterior longitudinal ligament bound the space posteriorly. Lying directly on the sacrum are the median sacral artery and vein. The artery originates from the dorsal aspect of the distal aorta (and not from the point of bifurcation, as some- times shown). The vein(s) drains into the left common iliac vein or vena cava. Caudal and lateral to this are the lateral sacral vessels, which drain into the internal iliac vein. The sacral venous plexus is formed primarily by these vessels but also receives contributions from the lumbar veins of the posterior abdominal wall and from the basivertebral veins that pass through the pelvic sacral foramina. The basivertebral veins are thin-walled vessels contained in large, tortuous channels in the can- cellous tissue of the bodies of the vertebrae. The sacral venous plexus formed by these vessels can be extensive, and bleeding from it can be considerable. The sacral promontory represents the most supe- rior aspect of the anterior surface of the first sacral vertebra and is a common bony landmark used dur- ing surgeries such as sacrocolpopexy, presacral neurec- tomy, and lymph node dissection. Great variability in the lumbosacral anatomy and fat content in the pre- sacral space may impede precise identification of this bony landmark. The ureters and common iliac and internal iliac vessels all lie within 3 cm from the mid- point of the promontory. The closest major vessel to the midsacral promontory is usually the left common iliac vein. The fifth lumbar to first sacral intervertebral disk is found just above the sacral promontory and is generally the most visible nonvascular structure noted intraoperatively. Within this area lies the most familiar part of the pelvic autonomic nervous system, the superior hypo- gastric plexus or presacral nerve (see FIG. 1.34 ). The autonomic nerves of the pelvic viscera can be divided into a sympathetic (thoracolumbar) and a parasympathetic system. The parasympathetic part of the autonomic division in the pelvis arises from the second through the fourth sacral nerve segments and is called the parasympathetic root (pelvic splanchnic nerves). The former is also called the adrenergic system, and the latter is called the cholinergic system, accord- ing to their neurotransmitters. α -Adrenergic stimula- tion causes increased urethral and vesical neck tone, and cholinergic stimulation increases contractility of the detrusor muscle. Similarly, adrenergic stimulation in the colon and rectum favors storage, and choliner- gic stimulation favors evacuation. β -Adrenergic ago- nists, which are used for tocolysis, suggest that these influence contractility of the uterus. As is true in the man, damage to the autonomic nerves during pelvic lymphadenectomy can have a significant influence on orgasmic function in the woman. Variable degrees of

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