Intra-abdominal Pelvic Anatomy
The anatomy pertinent to surgery of the uterus, adnexa, and neighboring pelvic structures is not only intraperitoneal but, perhaps more important, extraperitoneal.
Uterine Support
The main uterine support is provided by the cardinal ligaments, which extend from roughly the level of the cervicoisthmic junction peripherally in a fanlike fashion laterally and posteriorly, where it blends with the fat and fascia of the pelvic sidewall (Fig. 9–1). This ligamentous structure divides the pelvis into right and left paravesical spaces anteriorly and pararectal spaces posteriorly (Fig. 9–2A, B). The cardinal ligament can be divided into an upper portion at the junction of the uterus and cervix and a lower portion at the juncture of the cervix and vagina (Fig. 9–3).
The uterosacral ligaments connect to the cardinal ligaments at the cervical attachment of the latter and extend posteriorly and inferiorly toward the ischial spines and sacrum. However, these terminal attachments may be difficult to identify precisely (see Figs. 9–2 through 9–4). Between the uterosacral ligaments and covered by a peritoneal reflection onto the posterior aspect of the uterus is the top of the rectovaginal septum. This is the portal of entry to the rectouterine space.
The round ligaments arise from the anterolateral fundus and extend ventrally and laterally to the anterior abdominal wall, entering the inguinal canal and terminating in the fat of the labium majus on either side (Fig. 9–5). The round ligaments, in contrast to the other “ligaments,” are mainly composed of smooth muscle. The infundibulopelvic ligaments are in reality peritoneal vascular conduits, which carry the ovarian vessels from the posterolateral pelvic brim in an anteromedial direction to gain attachment to the uterus at the level of the cornua.
The broad ligament is a tentlike structure that comprises anterior and posterior peritoneum containing areolar fat (see Fig. 9–5). The “ligament” begins anteriorly at the round ligament and finishes posteriorly at the infundibulopelvic ligament.
FIGURE 9–1 The uterine fundus has been excised. The cardinal ligaments stretch from the cervix to the sidewall and are contiguous with the uterosacral ligaments and the paravesical, pararectal, and paravaginal fascia. Note the course of the ureters as they penetrate the cardinal ligaments.
FIGURE 9–2 A. The cardinal ligament may be divided into an upper portion at the junction of the uterine body and cervix and a lower portion at the junction of the cervix and vagina. B. The various anatomic spaces within the pelvis are schematically demonstrated.
FIGURE 9–3 The sagittal view demonstrates the relationships between the cardinal ligaments and the various anatomic spaces. Note that the sidewall largely consists of the obturator internus muscle mass and its fascia.
FIGURE 9–4 Sagittal view of the posterior pelvis shows the uterosacral ligaments, sacrospinous ligaments, and cardinal ligaments and their relationships to the viscera. Note the position of the ureter from this perspective.
FIGURE 9–5 The peritoneum has been opened, exposing the broad ligaments. This is the easiest portal of entry into the retroperitoneal space and the pelvic sidewall structures. The weblike fat contents are easily and bloodlessly dissected.
Pelvic Anatomy
Exposure of extraperitoneal structures must be accomplished safely and expeditiously. Access to the left ureter, left iliac vessels, and left ovarian vessels can be gained by sharply incising the peritoneal sidewall attachment of the sigmoid colon; more extensive exposure is offered by continuing the separation of the descending colon from the psoas major muscle (Fig. 9–6A, B). Similarly, opening the top of the broad ligament between the round and infundibulopelvic ligaments lateral to the pulsation of the external iliac artery (i.e., over the psoas major muscle) provides easy access to both right and left sidewall/retroperitoneal spaces (Fig. 9–7A–C). After entry to the retroperitoneum is gained, exposure of the pelvic ureter and uterine vascular supply requires incision of the broad ligament (Fig. 9–8A–D).
The course of the ureter from the point where it enters the pelvis to the point where it enters the bladder consists of anatomic landmarks that every obstetrician-gynecologist must know. The greatest number of surgery-related injuries to the ureter happens to the segment between the uterine artery crossing point and bladder entry. The uterine artery crosses the lower third of the pelvic ureter obliquely lateral and cephalad to the uterus. The ureter may be crossed again by the inferior vesical artery as it enters the bladder. The vaginal artery lies behind the ureter. The distal ureter is exceedingly close to anterolateral fornix of the vagina (Fig. 9–9A–I).
The ureters gain entry to the pelvis by crossing lateromedially over the psoas muscle; they cross the common iliac vessels at the point where the external and internal iliac arteries bifurcate (Fig. 9–10). The ureter descends into the pelvis medial to the internal iliac artery (hypogastric artery) and obturator fossa (Fig. 9–11). Its course is consistently one of deep descent and medial swing, particularly after the uterine artery crosses over it (superior and anterior). The entire course of the right ureter can be seen in Figure 9–12.
The left ureteral course is complicated by the position of the sigmoid colon overlying it and the presence of the inferior mesenteric vessels that supply the left colon (see Fig. 9–7A, B). The left ureter crosses the common iliac artery in concert with the ovarian arteries and descends into the pelvis, following a similar course to the right ureter. The ovarian vessels cross the common iliac in concert with the ureter. The ureter is behind the ovarian vascular pedicle and slightly medial to it (Figs. 9–13A–D and 9–14A).
The arterial blood supply to pelvic structures emanates from the abdominal aorta, which branches into right and left common iliac vessels at the L4–L5 vertebral level (Figs. 9–14B and 9–15 through 9–18A). To the right of the aortic bifurcation lies the origin of the inferior vena cava. The cava is formed by the union of left and right common iliac veins (Fig. 9–18B). The left common iliac veins cross in front of (anterior to) the sacrum within the bifurcation of the aorta and under the right common iliac artery to join the right common iliac vein, which lies posterior to the right common iliac artery (Figs. 9–18C, D). The inferior mesenteric artery arises from the lower left side of the abdominal aorta, giving off numerous branches to the left colon and sigmoid.
