Pelvic Exenteration

Anatomy and Physiology

Embryologic studies by Hockel identified urinary, genital, and digestive tract components to have a common origin in the "morphogenetic unit" of the pelvis. The 3 units separate with their associated vascular supply, mesenteries, and lymphatic drainage. The rectum, anus, and mesorectum originate from the hindgut. The Mullerian morphogenetic unit forms the Fallopian tubes, mesosalpinx, uterine corpus and cervix, mesometrium, proximal vagina, and mesocolpium. The distal ureters, urinary bladder, urethra, and distal vagina arise from the urogenital sinus and Wolf ducts. Initially, these separate units provide a natural barrier for the extension of a neoplasm to adjacent structures. Current oncologic surgical guidelines identify the importance of removing the entire unit, including the meso-viscera. According to Hockel's studies, radical compartmentalized surgery requires an en-bloc resection of the unit with affected viscera. Removal of 2 or more morphogenetic units represents an ultraradical compartmentalized surgery or pelvic exenteration.[10]

Current radical surgery expands the posterior compartment to include the sacrum with the rectum when necessary to achieve a complete (R0) resection. Likewise, the extension of an anterior compartment neoplasm might incorporate the pubic bone. The lateral extension of a pelvic neoplasm can require excision of the lateral compartment involving the vascular, neurologic, and muscular structures of the pelvic sidewall.[11]

Indications

Symptoms related to advanced or recurrent pelvic malignancies include intractable pain, bleeding, sepsis, obstruction, and fistula formations. Some symptoms can also be related to prior radiation therapy. The primary indication for pelvic exenteration is locally advanced carcinoma, both primary and recurrent. These lesions involve the contiguous pelvic organs or adjacent anatomy, including the pelvic sidewall, neurovascular structures, or the bony sacral or pubic components of the pelvis. The goal is to achieve a complete oncologic (R0) resection indicated by the absence of malignancy involving the resection margins.[3] Radical resection is meant to afford the patient a reasonable chance of cure, up to 63%.[3][1] The most important factor in predicting survival and quality of life for these advanced malignancies is an R0 resection.[12]

Historically, the triad of unilateral hydronephrosis, leg edema, and sciatic leg pain was indicative of unresectable pelvic sidewall disease. Extra-anatomic resections are now being performed with advanced preoperative planning utilizing pelvic magnetic resonance imaging (MRI), computed tomography (CT) angiograms, or CT venograms with R0 rates of 66.5%.[8]

Contraindications

The primary contraindication for pelvic exenteration is preoperative certainty that clear surgical margins free of malignancy (R0) will not be achievable in a patient well-informed of this risk. Because of the postoperative morbidity associated with pelvic exenteration, generally, exenteration should only be offered to patients with resectable disease and with a curative intent.[8] The palliative approach has not demonstrated improved quality of life but has modestly prolonged survival.[13] However, there is limited evidence on the quality of life following palliative pelvic exenteration. Therefore, it should be reserved for select individuals. Though the role of pelvic exenteration for palliative intent is not well defined, some consider patients with uncontrolled fistulas, fungating tumors, and intractable pain to be reasonable exceptions.[4][14]

The role of pelvic exenteration in patients with metastatic disease is also unknown. In general, pelvic exenteration should not be offered to patients who would not be candidates for adjuvant chemotherapy within conventional time frames following pelvic exenteration due to the anticipated prolonged recovery interval.[8]

Preparation

Pelvic exenteration is a major multi-visceral operative procedure with significant risks of morbidity and mortality. Preoperative evaluation of the patient should proceed with the gravity of the procedure as a guide. Cystoscopy, vaginal examination, and lower GI endoscopy are usually necessary to establish a diagnosis and to determine the extent of pelvic visceral involvement. For patients being considered for pelvic exenteration related to malignancy, histologic confirmation is imperative. The primary evaluation goals are to confirm the absence of metastatic disease and assess the patient's fitness to withstand an extended operative procedure with significant blood loss and fluid shifts.

CT scans of the chest, abdomen, and pelvis, along with positron emission tomography (PET) scans, are instrumental in searching for possible metastatic lesions. Open or directed biopsies are necessary for the pathologic review of suspicious abnormalities. High-resolution pelvic MRI is valuable to define the local extension of the lesion to adjacent pelvic structures.[8] Along with the MRI, CT arteriography and venogram are often beneficial to planning the pelvic resection to achieve R0 margins. Data has shown that PET/CT scans can alter treatment decisions in up to 40% of cases.[15][16][17]

Medical specialists are crucial in evaluating and optimizing the patient's cardiopulmonary reserve before undergoing pelvic exenteration. Potential extensive blood loss, fluid shifts, and surgical stress should be anticipated. Anesthesiology clinicians perform evaluations to determine the appropriate general and regional techniques to be employed. Adequate blood components should be secured and available for the procedure. Surgical specialists and critical care physicians continue to be responsible for different aspects of patient care during the postoperative phase.[18] With a multi-visceral resection, multiple surgical teams are frequently required and may remain on standby for all contingencies that can be anticipated. However, the lead surgeon develops the final surgery plan to resect the lesion with R0 margins completely.

Once a surgical plan is finalized, the enterostomal therapist must educate and mark the patient for needed ostomies. Physical therapists are involved with preconditioning therapy and planning postoperative recovery. Furthermore, patients needing pelvic exenteration are frequently malnourished. Therefore, total parenteral nutrition may be initiated before surgery and continued postoperatively after the return of adequate bowel function.[19] Attention should also be directed toward evaluating the patient's physical condition to tolerate pelvic exenteration. Determining the potential for a curative resection is also central to the planning. The healthcare team members must also assess the patient's psychosocial ability to tolerate pelvic exenteration, a prolonged recovery, and changes in self-image.

Patients undergoing pelvic exenteration are at high risk for pulmonary embolism. Mechanical compression devices are frequently utilized for deep vein thrombosis prophylaxis without the increased risk of bleeding that anticoagulants have. However, chemical prophylaxis should be individualized, with surgeons weighing the risks of intraoperative bleeding against the risk of a significant pulmonary embolism.[17]

Technique or Treatment

The patient is situated on the operating room table in a semi-lithotomy position, most commonly elevating and spreading the legs with Allen stirrups, which allow the abdomen and perineum to be prepped and accessed. Visualization of the pelvis is facilitated by placing the operating room table in the head-down (ie, Trendelenburg) position. Surgical exploration is performed through a midline incision. A thorough exploration of the abdominal cavity is performed to exclude any metastasis beyond the anticipated extent of pelvic resection, including evaluation of the liver, spleen, gastrointestinal viscera, omentum, and peritoneal surfaces.

Dissection is initiated by incising the peritoneum overlying the iliac vessels and mobilizing the node-bearing tissue medially to include it with the specimen. The arterial iliac branches to the specimen are ligated along with the cardinal ligament in females. The peritoneum of the anterior bladder is incised to mobilize the bladder posterior with the specimen. Each ureter is ligated proximal to the tumor and preserved to reestablish urinary outflow. In males, the anterior dissection is carried to the pelvic floor to mobilize the prostate, and the urethra is ligated. In females, the dissection is also carried down to the pelvic floor and terminated at the urethra and vagina. Posteriorly, the inferior mesenteric pedicle is ligated at or above the aortic bifurcation. The sigmoid mesentery is divided, preserving the remaining blood supply, and the sigmoid colon is transected in preparation for a colostomy. The rectum is mobilized from the presacral fascia posteriorly to ensure a total mesorectal excision beyond the tip of the coccyx. The dissection is continued bilaterally along the fascia of the pelvic sidewalls until the rectum and vagina or prostate are fully mobilized to the pelvic floor. To complete the resection, the remaining perineal attachments are excised. An elliptical incision is made on each side of the anus, beginning just anterior to the coccyx. The anterior extent of the incision is carried across the perineum at the base of the scrotum in males or incorporating the vaginal introitus up to the clitoris in females. The soft tissues are then divided down to the pelvic floor musculature. The pelvic floor is divided from the coccyx to the ischial tuberosities at the lateral extent and anterior to the urethral hiatus. The specimen, including the rectum, anus, vagina or prostate, and bladder, can be passed from the operative field as an en-bloc resection.

Reconstruction following the resection is extensive. The pelvic floor defect can be closed with either a polypropylene mesh and covered with local soft tissue mobilization (eg, the omentum), or the defect can be closed with a rectus abdominus myocutaneous flap. Occasionally, gracilis myocutaneous flaps can be used to reconstruct the pelvic floor or create a neovagina. Vaginal reconstruction is also performed with skin grafts or an isolated segment of the bowel. For urinary outflow, a segment of vascularized ileum is isolated from the distal small bowel. Bowel continuity is restored with a proximal to distal segment enteroenterostomy. The ureters are implanted into the isolated segment of the ileum. The resulting ileal conduit (ie, Bricker pouch) is "matured" by everting the right lower quadrant abdominal wall defect and suturing the edges to the skin, creating a urostomy. A continent urostomy has been popularized using the transverse colon and ileocecum. The transverse colon is fashioned as a pouch, and the ureters are implanted. Either the residual terminal ileum or appendix is matured to the skin. The patient periodically catheterizes the stoma to evacuate urine. An additional advantage of the continent conduit is that the transverse colon is relatively spared from radiation, reducing the risk of urinary fistulas.[20] The reconstruction is completed by maturing the proximal sigmoid colon to the skin via a left lower quadrant abdominal wall defect.

The urinary structures are preserved in a partial or posterior pelvic exenteration in a female. The uterus and vagina are mobilized from the bladder in the anterior plane. The anterior dissection is carried to the pelvic floor, and the perineal excision preserves a cuff of the vagina at the urethral orifice to facilitate urinary outflow. For a partial or anterior pelvic exenteration in a female, the bladder and gynecologic structures are resected en bloc while preserving the rectum and anus. The perineal excision is carried out anterior to the anus with complete excision of the vaginal introitus.

For locally advanced tumors involving the pelvic sidewalls, the internal iliac artery, and vein can be ligated and divided to access the extra-fascial plane lateral to these structures.[21] The locally advanced disease might also necessitate resection of an involved sacrum or pubis. Additional variations of pelvic exenteration involve the preservation of the pelvic floor. When adequate tumor margins can be obtained without resecting the pelvic floor musculature, the rectum and the vagina can be divided and closed above the pelvic floor. When the anal sphincter can be preserved, bowel continuity can be restored with either a low anterior or coloanal anastomosis with a temporary diverting loop ileostomy for protection. 

Complex multi-visceral and extended resections during a pelvic exenteration are associated with prolonged operative times ranging from 5 to 14 hours and substantial blood loss.[3] The technique for robotic pelvic exenteration procedures has been described, and the goals are the same as an open procedure.[9][22][23]

Complications

Currently, morbidity related to pelvic exenteration ranges from 20% to 80%.[8] In a pooled study, the median in-hospital morbidity was 53.6%; the median hospital stay was 22 days, ranging from 8 to 51 days; and the in-hospital mortality was 6.3% on average, ranging from 0% to 66.7%.[4]

In preoperative radiation and revision surgery, urologic morbidity is high, between 9% and 24%, with urinary leak rates of 7% to 16%.[3] The anastomotic leak rate has been reported as 6% for patients with gastrointestinal anastomosis of all types.[24] The leak rate for low anterior colon anastomoses is as high as 54%.[25] Pelvic abscesses and enteric fistulas have been noted in up to 15% of patients with an empty, irradiated pelvis.[26] Techniques using the omentum to suspend the bowel and ileal conduit out of the pelvis or fill the pelvis have reduced the abscesses and fistulas.[27][28] Up to one-third of pelvic exenteration patients require further interventions to manage complications.[29] [30][31] To address the complications related to sepsis and malnutrition, policies to include 5 days of post-operative antibiotics and total parenteral nutrition until the return of gastrointestinal function have been adopted.[8]

Clinical Significance

Since the mid-1900s, when the mortality for pelvic exenteration was approximately 23%, mortalities are now as low as 1% to 2% in specialized centers.[8] The most critical factor for long-term survival following pelvic exenteration is achieving an R0 resection.[29] For patients with advanced primary or recurrent pelvic malignancies, surgical resection is the only potentially curative intervention. Across various primary pathologies, a 3-year survival of ≥50% was achieved with R0 resections. R0 resections can be achieved in approximately 70% of appropriately selected patients.[29] In a 30-year review, pelvic exenteration is now being performed more for recurrent disease as opposed to primary tumor resections.[24]

The use of pelvic exenteration for advanced cervical, vaginal, and vulvar cancers has diminished secondary to improved primary malignancy responsiveness to current chemoradiation techniques.[20] For palliative pelvic exenteration, the in-hospital mortality has been demonstrated to be 6.3%, with a median overall survival of 14 months.[4] Due to high morbidity rates and limited overall survival, pelvic exenteration for palliative intent remains controversial. Studies have also only demonstrated limited evidence of symptom control and improved quality of life. Controversial data has shown the quality of life with palliative pelvic exenteration compared to patients with rapidly enhanced quality of life over 2 to 9 months following curative surgery.[4] Minimally invasive techniques associated with pelvic exenteration are continuing to develop. Studies have demonstrated that minimally invasive approaches are feasible for pelvic exenteration, resulting in less intraoperative blood loss and shorter hospital stays; however, extensive studies are unavailable.[32]

Enhancing Healthcare Team Outcomes

Specialized tertiary care centers that perform pelvic exenteration have been demonstrated to achieve improved long-term survival and surgical outcomes.[29] Pelvic exenteration is a major surgical undertaking for the patient and surgical team. Specialized support is required from radiology, anesthesia, chronic pain specialists, oncologists, and critical care physicians. Allied health specialty support is needed for physical therapy and enterostomal therapy. To prepare for the prolonged recovery with home health or rehabilitation medicine, coordination with the hospital administration and social services is paramount. Physicians who perform pelvic exenterations either alone or as members of a team include general surgeons, oncologic surgeons, colon and rectal surgeons, gynecologists, gynecologic oncology surgeons, urologists, plastic surgeons, orthopedic surgeons, and neurosurgeons.

Pelvic exenteration is a complex operative procedure for patients with advanced primary or recurrent malignancies or complications related to the prior treatment for pelvic malignancies. These complex and varied procedures are individualized for each patient’s special needs. Thus, pelvic exenteration does not lend itself to standard controlled trials for the evaluation of management and outcomes. The PelvEx Collaborative has been established to provide a large volume of “real world” data that allows studies to improve outcomes related to exenterative surgery.[29] Over 100 international specialized units across 5 continents are contributing standardized data for ongoing studies. To date, the PelvEx Collaborative is responsible for 8 publications.[33][34][35][36][37]