Video Clips on DVD
Anterior Abdominal Wall
Anatomy of the Uterus and Adnexa
Lower Urinary Tract
Avascular Planes of the Pelvis
The removal of the uterus may be performed through a variety of approaches: abdominal, laparoscopic, and vaginal. In order to effectively perform a hysterectomy, the surgeon should have an intimate knowledge of the anatomy of the anterior abdominal wall and the pelvis in order to safely attain access, maximize exposure, secure vascular pedicles, and avoid injury to the surrounding vasculature, nerves, and viscera. This chapter will discuss the surgical anatomy of the pelvis focusing specifically on the anatomic relationships necessary for the surgical removal of the uterus.
Anterior Abdominal Wall
The most common approach to hysterectomy in the United States is the abdominal one, although the laparoscopic approach is also gaining in popularity. For these approaches, the surgeon must access the intra-abdominal cavity via the anterior abdominal wall, which is primarily accessed below or at the level of the umbilicus.
Surface anatomy and bony landmarks can aid the surgeon to identify underlying structures and appropriately plan surgical incisions or laparoscopic trocar placement. The umbilicus marks the approximate location of where the aorta bifurcates into the right and left common iliac arteries. The anterior superior iliac spines are where the inguinal ligaments originate, and the pubic symphysis is where the inguinal ligaments as well as the rectus abdominis muscles insert ( Fig. 2-1 ).
From superficial to deep, the abdominal wall consists of skin, subcutaneous fat, Camper’s fascia, Scarpa’s fascia, rectus sheath, rectus muscles, and parietal peritoneum. Camper’s fascia consists of a fatty layer that is not easily appreciated, while Scarpa’s fascia presents as a thin fibrous layer that may be fused with the rectus fascial sheath. The rectus sheath is composed of the aponeuroses of the external oblique, internal oblique, and transversus abdominis (or transversalis) muscles. Above the arcuate line (located approximately one half of the distance between the umbilicus and the pubic symphysis), the rectus sheath divides into an anterior and posterior sheath. The anterior sheath is located anterior to the rectus muscles and consists of the aponeuroses of the external oblique, and the anterior layer of the internal oblique, and the posterior sheath consists of the aponeuroses of transversus abdominis muscle and the posterior layer of the internal oblique and is located posterior to the rectus muscles. Below the arcuate line, all layers of the rectus sheath are fused and located anterior to the rectus muscles ( Fig. 2-2 ). The rectus fascia is the most important layer for closure of the anterior abdominal wall. Successful closure of this layer prevents herniation, incarceration, or evisceration of the abdominal contents. Because of the primarily transverse orientation of the abdominal wall muscle fibers, reapproximation of a vertical suture line in the rectus fascia is under more tension compared to transverse incisions, making vertical incisions more prone to dehiscence. The rectus muscles fuse in the midline at the linea alba. The pyramidalis muscle arises from the pubic bone, is located anterior to the rectus muscles, and inserts into the linea alba several centimeters above the pubic symphysis.
The inguinal ligament is the anatomic boundary between the abdomen and the thigh. The round ligament travels through the inguinal canal and terminates at the labia majora. Additionally, the ilioinguinal nerve and the genital branch of the genitofemoral nerve pass through the inguinal canal. As the external iliac vessels cross underneath the inguinal ligament, they become the femoral artery and vein. The inferior epigastric artery originates off the external iliac artery just before it becomes the femoral artery and travels through the transversalis fascia into a space between the rectus muscle and posterior sheath. The inferior epigastric vessels travel from their lateral origins obliquely toward a more medial location as they approach the umbilicus ( Fig. 2-3 ). The superficial epigastric vessels originate from the femoral vessels and branch extensively as they approach the umbilicus. These superficial vessels can be transilluminated through the anterior abdominal wall during laparoscopy but the inferior epigastric vessels must be visualized intra-abdominally where they run lateral to the medial umbilical ligaments. (See DVD Video 2-1 for video demonstration of the anatomy of the anterior abdominal wall. )
Of the incisions commonly used in gynecologic surgery, the vertical midline incision affords the best visualization and most rapid entry, but at the cost of increased postoperative pain and risk of wound dehiscence and ventral hernias. It usually extends from just below the umbilicus to the pubic symphysis, but can be extended cephalad to the xiphoid process if exposure to the upper abdomen is required. After incising through the skin, subcutaneous fat, and Scarpa’s fascia, the rectus sheath is opened in a vertical fashion and the rectus muscles are then divided and the posterior rectus sheath (above the arcuate line) and peritoneum are opened in order to access the intraperitoneal contents ( Fig. 2-4 ).
The transverse incisions used in gynecologic surgery are the Pfannenstiel, Maylard, and Cherney incisions. Compared to vertical incisions, these transverse incisions have the advantages of improved cosmesis and wound healing and less postoperative pain. These incisions can be categorized into muscle-sparing (Pfannenstiel) and muscle-splitting (Maylard and Cherney) incisions. The Pfannenstiel and Maylard incisions are made approximately two fingerbreadths above the pubic symphysis ( Fig. 2-5 ). For the Pfannenstiel incision, the skin, subcutaneous fat, Camper’s and Scarpa’s fasciae, and rectus sheath are transected in a transverse fashion; then the rectus fascia are dissected off the underlying rectus muscles and muscles are separated vertically in the midline (i.e., muscle sparing) in order to gain access to the peritoneum and intra-abdominal cavity. In order to perform the Maylard incision, after making a transverse incision in the rectus fascia the surgeon incises the rectus muscles in a transverse fashion (i.e., muscle splitting) starting from the midline and working laterally without dissecting the rectus muscles off the overlying rectus sheath. The inferior epigastric vessels must be identified (usually around 6 to 7 cm lateral from the midline) and ligated prior to transecting the rectus muscles laterally ( Fig. 2-6 ). The Maylard incision affords better visualization and access than the Pfannenstiel incision, but at the cost of increased postoperative pain and discomfort. In contrast to the Maylard and Pfannenstiel incisions, the Cherney incision is performed 1 cm above the pubic symphysis, but is performed in a similar fashion until the rectus muscles are reached. The rectus muscles are then dissected off their insertion on the pubic symphysis and are reflected cephalad after ligating the inferior epigastric vessels as they enter the rectus muscles obliquely ( Fig. 2-7 ). This incision is most often used for retropubic procedures (e.g., the Burch urethropexy or paravaginal defect repair).
The iliohypogastric and ilioinguinal nerves are sensory nerves that may be damaged with low transverse incisions and lower abdominal laparoscopic trocar placement. Such an injury can result in neuropathic chronic pain syndromes consisting of burning pain and altered skin sensitivity in the affected region. The iliohypogastric nerve innervates the skin of the suprapubic area, while the ilioinguinal nerve innervates the groin area, upper labial majora, and upper medial thigh. The iliohypogastric nerve enters the abdominal wall approximately 2 cm medial and 1 cm inferior to the anterior superior iliac spine and travels obliquely, terminating 3.7 cm lateral to the midline and 5 cm above the pubic symphysis. The ilioinguinal nerve enters the abdominal wall 3 cm medial and 3.7 cm inferior to the anterior superior iliac spine, traveling obliquely to terminate 2.7 cm lateral to the midline and 1.7 cm above the pubic symphysis. Injuries to these nerves may be averted during laparoscopy by placing the lower abdominal trocars 2 cm medial and superior to the anterior superior iliac spines ( Fig. 2-8 ). Nerve entrapment may also occur during the lateral closure of transverse incisions as the paths of these nerves unavoidably traverse the lateral aspect of these incisions. Patients who complain of burning pain in the lower abdomen, pelvic area, and upper medial thigh that increases with Valsalva maneuver and that is not relieved with narcotics but improves with hip flexion and forward leaning of the trunk should undergo a diagnostic and therapeutic trial of local anesthetic injection at a site approximately 3 cm medial to the anterior superior iliac spine where the nerves originate.
The parietal peritoneum is often covered by preperitoneal fat, and is located just below the rectus muscles. The median umbilical ligament is caused by the presence of the urachus, and is a vertical structure located in the midline. The medial umbilical ligaments are paired structures consisting of the obliterated umbilical arteries, which connect the internal iliac vessels to the umbilical cord, and are located laterally to the median umbilical ligament ( Fig. 2-9 ). The medial umbilical ligaments are an important landmark in locating the inferior epigastric vessels during the placement of lower abdominal ports during laparoscopy, as the vessels are located laterally to the medial umbilical ligaments. During laparoscopy, after the umbilical trocar is placed, the anterior superior iliac spine (ASIS) is palpated and the lower abdominal trocar should be inserted two fingerbreadths medial and superior to the ASIS, lateral to the medial umbilical ligaments and the inferior epigastric vessels ( Fig. 2-10 ). The medial umbilical ligaments also form the boundaries of the dome of the bladder, which is contiguous with the parietal peritoneum and located cephalad to the pubic symphysis. Entry into the abdominal cavity necessitates caution as one travels caudally, and initial entry should be performed cephalad toward the umbilicus and the peritoneum and then taken down in layers as one approaches the pubic symphysis in order to avoid bladder injury. Because the apex of the bladder is triangular in shape, and is highest in the midline, incising the peritoneum laterally as you approach the pubic symphysis is less likely to result in visceral injury.
Uterus and Adnexa
The uterus consists of the uterine corpus and the cervix. The corpus, or body of the uterus, consists of an inverted triangular endometrial cavity surrounded by the myometrium and serosa ( Fig. 2-11 ). The portion of the uterus superior to the endometrial cavity is called the fundus of the uterus. The cervix is the conduit between the endometrial cavity and the vagina. In the reproductive-aged female, the corpus is much larger than the cervix, while in prepubertal and postmenopausal females, their relative length is similar. However, the overall size of the uterus can vary considerably, depending on hormonal levels, previous parturition, or the presence of fibroids or adenomyosis.
The myometrium consists of muscle fibers that crisscross diagonally with those of the other side. The endometrium lines the uterine cavity, with a superficial layer that consists of columnar epithelium and stroma that changes with the menstrual cycle, which is supplied by spiral arteries that spasm and cause the shedding of this layer with each menses. A deeper basal layer, supplied by different arteries, regenerates a new layer after each menstrual cycle.
The cervix is composed of dense fibrous connective tissue with a minimal amount of smooth muscle located on the periphery that connects the myometrium to the muscle in the vaginal wall. This smooth muscle layer surrounds the cervix, and is where the cardinal and uterosacral ligaments insert. The internal os is the opening of the endocervical canal into the endometrial cavity, while the external os is the opening of the canal on the vaginal side. At the external os the columnar epithelium that extends from the endocervical canal transforms into stratified squamous epithelium upon exposure to the acidic environment of the vagina that occurs with the onset of puberty and the effects of estrogen. This area is known as the transition zone and is susceptible to dysplastic and malignant transformation.
The broad ligament covers the lateral uterine corpus and upper cervix, and extends superiorly to the round ligaments and posteriorly to the infundibulopelvic ligaments. It consists of anterior and posterior leafs, and is composed of visceral and parietal peritoneal layers containing smooth muscle, vessels, and connective tissue, and is not the type of ligament associated with skeletal joints. The cardinal and uterosacral ligaments lie below the broad ligament, while the round ligaments, tubes, and ovaries lie at its upper margins. Various portions of the broad ligament are named for nearby structures, for example, the mesosalpinx (located near the fallopian tubes) and the mesovarium (located near the ovary) ( Fig. 2-12 ).
The round ligaments are extensions of the uterine musculature. They begin at the anterior lateral aspects of the fundus, travel through the retroperitoneum, then enter the inguinal canal and terminate at the labia majora ( Fig. 2-13 ). The male homologue is the gubernaculum testis.
The uterine adnexa consist of the fallopian tubes and ovaries. The fallopian tubes connect the endometrial cavity to the intra-abdominal cavity. They arise from the uterine corpus posterior to the round ligaments. Each tube is divided into four distinct areas: the interstitial portion, where the tube passes through the cornu; the isthmus , with a narrow lumen and thick muscular wall; the ampulla , with a larger lumen and mucosal folds; and the fimbria , located at the end of the tube with frondlike projections that increase the surface area for ovum pick-up. The outer muscularis layer of the tube consists of longitudinal fibers and the inner layer consists of circular fibers.
The ovary is connected medially to the uterus through the utero-ovarian ligament; laterally it is connected to the pelvic sidewall through the infundibulopelvic ligament (also known as the suspensory ligament of the ovary) through which the ovarian vessels travel ( Fig. 2-14 ). It is also attached to the broad ligament through the mesovarium. The ovary consists of an outer cortex, where the ova and follicles are located, and medulla, where the blood vessels and connective tissue compose a fibromuscular tissue layer. (See DVD Video 2-2 for video demonstration of the anatomy of the uterus and adnexa. )
Uterine Support Structures
The pelvic viscera are covered by endopelvic fascia, a connective tissue layer that provides support to the pelvic organs, yet allows for their mobility to permit storage of urine and stool, coitus, parturition, and defecation. Histologically, it is composed of collagen, elastin, adipose tissue, nerves, vessels, lymph channels, and smooth muscle. Several areas of the endopelvic fascia (and its associated peritoneum) have been named by anatomists. These are really condensations of the endopelvic fascia and not true ligaments: uterosacral ligament, cardinal ligament, broad ligament, mesovarium, mesosalpinx, and the round ligament. The principal connective tissue support structures for the uterus are the cardinal ligaments and the uterosacral ligaments. These two structures are intimately related and together form an intricate three-dimensional connective tissue structure that originates at the cervix and upper vagina and inserts at the pelvic sidewall and sacrum and is sometimes called the uterosacral/cardinal complex. The broad ligament, mesovarium, mesosalpinx, and round ligament do not play a role in support of the pelvic organs.
Three levels of connective tissue supports of the uterus and vagina have been described ( Fig. 2-15 ). The uterosacral/cardinal ligament complex provides level I support. The uterosacral/cardinal ligament complex suspends the uterus and upper vagina in its normal orientation. It serves to maintain vaginal length and keep the vaginal axis nearly horizontal in a standing woman so that it can be supported by the levator ani muscles. Loss of level I support contributes to prolapse of the uterus. At the time of hysterectomy, care should be taken to incorporate the detached uterosacral/cardinal ligament remnants into the vaginal cuff repair in an attempt to preserve apical support of the vagina and subsequent prolapse. Any symptomatic vaginal support defects should also be addressed at the time of hysterectomy.