Pelvic dissection is inherent to the management of many rectal, urologic, and gynecologic conditions, and operating deep in the pelvis requires an intimate knowledge of the anatomy of this region. Whether performed in an open, laparoscopic, or robotic manner, surgery must be precise to avoid violating cancer planes and to prevent nerve damage and pelvic bleeding. The greatest challenges are posed by reoperative pelvic surgery and surgery in the presence of pelvic inflammation or bulky ultra-low rectal cancers, or when extensive pelvic fibrosis and obliteration of planes is present as a result of recurrent tumors or treatment with radiation.
Presacral hemorrhage is one of the most feared complications of pelvic surgery. An incidence of 9.4% and a mortality of 4.3% have been reported. When discussing the prevention and management of hemorrhage that occurs during pelvic surgery, it is helpful to outline the relevant anatomy, as well as the principles of pelvic bleeding and tactics for controlling it.
The pelvis is a bony and muscular cone, bounded posteriorly by the sacrum and coccyx and the piriformis and coccygeal muscles; anteriorly by parts of obturator internus, levator ani and the pubic bone; laterally by the ilium and ischium, obturator internus, and superior part of levator ani; and inferiorly by the levator ani muscles. The pelvis contains the rectum, distal sigmoid colon, bladder, and distal ureters, as well as ovaries, fallopian tubes, uterus and vagina in women and seminal vesicles, ductus deferentes, ejaculatory ducts, and prostate in men.
The taeniae coli coalesce to form a complete longitudinal muscle coat of the rectum as the sigmoid terminates. The rectum lacks epiploic appendices, haustrae, and a well-defined mesentery. The posterior rectal wall lies in the sacral hollow and is entirely extraperitoneal, whereas the upper rectum is invested by peritoneum anteriorly and laterally and the middle third only anteriorly. The lower third of the rectum is entirely extraperitoneal because the anterior peritoneal reflection is found at 7.5 to 5.0 cm from the anal verge in women and at 9.0 to 7.0 cm from the anal verge in men. Anteriorly, the rectum is in close proximity to the cervix and posterior vagina in women and is closely related to the prostate, seminal vesicles, and bladder in men. It is separated from these structures by the fascia of Denonvilliers. The fascia propria of the rectum is an extension of the parietal endopelvic fascia that lines the floor and walls of the pelvis and encloses rectum, adipose tissue, and blood and lymphatic vessels. It is more obvious laterally and posteriorly. The lateral ligaments of the rectum contain connective tissue and nerves and, in 25% of patients, branches of the middle rectal artery. It is important to note that the middle rectal arteries and pelvic plexus run underneath the lateral ligaments. The presacral fascia covers the concavity of the sacrum and coccyx, and the presacral nerves, middle sacral artery, and presacral veins run behind it ( Fig. 87-1 ).
During posterior rectal dissection, it is important to keep in the avascular plane between fascia propria of the rectum and the presacral fascia, anterior to the hypogastric nerves. Dissection deep to the presacral fascia can cause life-threatening venous bleeding. The venous plexus is particularly at risk deep in the presacral hollow when, in taking the dissection posteriorly down to the pelvic floor, the surgeon does not recognize the anterior curve of the sacrum and enters the presacral veins. The presacral venous plexus is formed by the two lateral sacral veins, the middle sacral vein, and communicating veins ( Fig. 87-2 ). These veins have no valves and communicate via the basivertebral veins in the internal vertebral venous system. The adventitia of the basivertebral veins is fixed to the sacral periosteum at the margins of the sacral foramina mainly at the level of S3-S4. In the lithotomy position, presacral veins can reach hydrostatic pressures up to three times the normal pressure of the inferior vena cava. Retraction of the cut end of the vein into a sacral foramen also can be a problem when the presacral fascia is violated, preventing control by simple tie or suture ligation.
The visceral pelvic fascia of Denonvilliers is a fascial layer that separates the extraperitoneal rectum anteriorly from the prostate and seminal vesicles or vagina. The mesorectal plane represents the continuation of the same plane of posterior and lateral dissection of the rectum. This natural anatomic plane is located between the parietal and visceral pelvic fascia and is the embryologic basis of a total mesorectal dissection ( Fig. 87-3 ). Sharp and precise dissection in this plane should be bloodless. Bleeding should raise the question of an improper plane of dissection. Blunt dissection, particularly with a hand in the presacral space, runs the risk of tearing the mesentery and avulsing vessels, causing both bleeding and an inadequate total mesorectal excision.
Just above its bifurcation, the aorta gives rise to the middle sacral artery. The analogous middle sacral vein drains into the left common iliac vein. The internal iliac arteries represent the main arterial supply to the pelvis through posterior and anterior trunks. On the viscera, these arteries anastomose with each other, providing collateral circulation between the left and right sides of the pelvis. The veins correspond to the branches of the artery. The posterior trunk is composed of the iliolumbar, lateral sacral, and superior gluteal arteries. The lateral sacral artery supplies the vertebral contents and enters the first and or second anterior sacral foramen. The superior gluteal artery courses posteriorly and leaves the pelvis through the greater sciatic foramen. The anterior trunk of the internal iliac artery is long when compared with the posterior trunk and is closely related to the lateral pelvic wall.
The first branch of the anterior trunk is the obturator artery. It extends forward along the pelvic wall against the fascia over the obturator muscle and leaves the pelvis via the obturator canal. The umbilical artery is the second branch. It runs parallel to or just above the pelvic brim and turns onto the anterior abdominal wall lateral to the bladder. The inferior vesical artery is typically the next branch and supplies the bladder. The middle hemorrhoidal artery is also a branch of the internal iliac anterior trunk; however, it is present in only 10% to 60% of dissections and has variable contribution to the rectal blood supply. It traverses the pelvis on the superior aspect of the levator ani. It does not travel directly through lateral stalks, but its branches may run through them ( Fig. 87-4 ). The middle hemorrhoidal artery reaches the lower third of the rectum anterolaterally, close to the level of the pelvic floor and deep to the levator fascia. It is prone to be injured during low anterior resection, when anterolateral dissection of the rectum is performed close to the pelvic floor and the prostate and seminal vesicles or upper part of the vagina are being separated from it. The anterior trunk of the internal iliac finally bifurcates into the inferior gluteal and pudendal arteries. The internal pudendal courses down on the anterior surface of the sacral plexus. The pudendal vessels then send branches medially to the pelvic floor, anal sphincters (inferior hemorrhoidal artery), and genitalia.
The superior hemorrhoidal artery is the direct continuation of the inferior mesenteric artery. It divides within the mesorectum at the level of S3 into descending right and left branches to the rectum. Within the submucosa of the rectum, these branches run straight downward to supply the lower rectum and anal canal. As these branches reach the rectal columns, they condense into capillary plexi in locations corresponding to internal hemorrhoidal groups, right posterior, right anterior, and left lateral positions.
Avoiding pelvic bleeding without compromising the intended surgery is always the primary goal, but because of the complex anatomy of the pelvis, bleeding may occur even during procedures performed by the most experienced of surgeons. Preparation for this eventuality is hence the key to containing it. In preoperative planning, one must consider the challenges of the procedure, disease, and body habitus. Difficult dissections are anticipated in patients with recurrent or bulky tumors, morbid obesity with bulky peritoneal fat, tumors in the distal third of the rectum, and a narrow pelvis in men. Typing and cross-matching of blood should be performed for any pelvic surgery. The anesthesiologist should have good venous access prior to the start of the procedure.
When major pelvic bleeding is encountered, several points are important. The need for additional trocars or hands to aid in retraction must be anticipated. Good communication with the operating room staff and the anesthesia team is essential, and extra suction catheters may be necessary. The best initial management is direct pressure, either with a finger, a sponge on a stick, or a pack at the site of bleeding. Once direct pressure is applied, the anesthesia team should be notified of the blood loss and the potential for further loss, and time is required for the loss to be caught up and for further products to be made available. Delivery of the specimen with the packing in place should be performed if possible because it allows better visualization of the presacral region.