Cancer of the Rectum: Operative Management

Introduction

Two decades ago, surgery for rectal cancer was associated with local recurrence rates as high as 30% and poor long-term overall survival. However, during the past 10 years, survival has significantly improved and the local recurrence rate has decreased. Several important factors have contributed to this increase in overall survival for patients with rectal cancer, including new regimens for radiotherapy/chemotherapy, centralization of surgical practice, and multidisciplinary treatment. However, the most important single factor for increased survival has been the paradigm shift related to surgical technique.

In the early 1980s, attention was focused on the “holy plane” between the fascia propria of the rectum and the presacral fascia, and a dissection technique within this plane was proposed that would keep the mesorectal fascia intact. This total mesorectal excision dramatically reduced local recurrence rates to 5% to 10% and increased the overall 5-year survival among patients with rectal cancer to about 71%. This significant improvement in outcomes has led to widespread acceptance of total mesorectal excision as the standard technique for surgical treatment of rectal cancer.

The second technical issue affecting rectal cancer surgery has been the evolution of minimally invasive surgery. During the past decade, laparoscopic rectal cancer surgery has been associated with less postoperative pain, shorter hospital length of stay, and lower readmission rates. Laparoscopic surgery has increasingly been accepted as the standard approach to rectal cancer resection. Oncologic outcomes appear to be similar to those of open surgery, although data from some newer trials are pending.

This chapter outlines the principles of radical surgery for rectal cancer based on our experience and publications. Transanal excision is covered in a separate chapter. Important surgical decision-making choices will be highlighted, and a stepwise approach to the operative management of rectal cancer will be described.

Key Anatomic Points

An intimate working knowledge of the anatomy of the rectum is a prerequisite to safe, effective proctectomy.

The inferior mesenteric artery (IMA) supplies blood to the descending colon, sigmoid colon, and upper rectum. It arises from the anterior aspect of the aorta and passes downward at the base of the sigmoid mesentery to the left iliac fossa. The IMA crosses the pelvic brim and then descends within the mesorectum as the superior hemorrhoidal artery. The other branches of the IMA are the left colic artery, which is the most proximal branch, and the sigmoid arteries. The inferior mesenteric vein (IMV) runs parallel to the IMA but continues cephalad to the origin of the IMA up to and behind the tail of the pancreas. High ligation of the IMA preserves the collateral arterial arcade to the left colon and, in combination with high ligation of the IMV, allows well vascularized descending colon to reach the anus for anastomosis. The left ureter lies in the retroperitoneum, behind the sigmoid mesentery and lateral to the gonadal vessels. It can be identified posterolaterally as it crosses over the internal iliac artery and vein, posterior to Toldt’s fascia, to run around the pelvic side wall on its way to the bladder. The inferior hypogastric plexus lies behind the IMA at the pelvic brim, receiving the hypogastric nerves and contributing sympathetic fibers to the pelvic plexus. The pelvic plexus is composed of these sympathetic fibers and parasympathetic nerves from L2 and L3. It lies on the pelvic sidewall like a fan, buried below the endopelvic fascia and safe from harm except anteriorly, where the terminal fibers pass to the seminal vesicles and prostate and penis, deep to Denonvilliers fascia. The risk of damage to this plexus is low, unless the endopelvic fascia or Denonvilliers fascia is breached during the pelvic dissection.

The mesorectum is a distinct anatomic unit composed of the rectum, perirectal fat, blood vessels, nerves, and lymphatic vessels. A layer of fibroareolar tissue called the mesorectal fascia surrounds the mesorectum, and dissection along the surface of mesorectal fascia is the key to successful surgical treatment of rectal cancer. Staying in the loose areolar tissue between the mesorectal and endopelvic fascia minimizes blood loss and protects the surrounding neurovascular anatomy. Anteriorly, the posterior vaginal venous system in females lies close, as do the seminal vesicles and prostate in men. These structures can be a source of bleeding during dissection of the low rectum; however, if dissection stays on the rectal side of Denonvilliers fascia, no bleeding occurs at all. Because dissection anterior to Denonvilliers fascia increases bleeding and places the neurovascular bundles at risk, it is only performed for locally invasive anterior tumors.

Presurgical Patient Preparation and Evaluation

1.
Preoperative cancer staging and planning for neoadjuvant radiotherapy/chemotherapy are performed in a multidisciplinary setting. The methods of staging and preoperative patient examination are described in another chapter; however, we favor staging with pelvic magnetic resonance imaging (MRI) using a standardized rectal cancer protocol.
2.
Functional sphincter status and defecation pattern: Preoperative evaluation of continence is an important predictor of postoperative results. Patients should be informed about expected postoperative changes in defecation and the possibility of soiling, especially with intersphincteric resection. The history should include assessment of preoperative fecal continence including nighttime soiling and incontinence relating to liquids, solids, or gas.
3.
Preoperative anesthesia and cardiac and pulmonary assessment is performed, including blood typing and complete blood count. We tend to cross-match only patients with antibodies or those undergoing extended resections, because transfusion rates are low.
4.
Preoperative bowel preparation: We use mechanical bowel preparation for patients undergoing rectal cancer surgery, especially when a diversion procedure will be used.
5.
Thrombosis prevention: Subcutaneous low-dose molecular heparin is administered prior to the induction of anesthesia, in conjunction with use of pneumatic compression devices.
6.
Antibiotics: For patients undergoing colorectal resection, we use a combination of oral neomycin and metronidazole, as well as intravenous antibiotic prophylaxis against both anaerobes and aerobes, which is not continued after surgery.
7.
The duration of preoperative fasting should be 2 hours for liquids and 6 hours for solids. Patients undergo carbohydrate loading preoperatively.
8.
Marking for patients requiring a permanent or temporary ostomy is performed preoperatively.

Preoperative Decision Making

Surgery is planned after careful review of preoperative imaging. For most cases, review by a multidisciplinary team is required. Any tumor extension seen on the preoperative and prechemotherapy/radiotherapy MRI is an indication for neoadjuvant therapy and may require surgery outside the total mesorectal excision (TME) plane.

Deciding Between an Open or Laparoscopic Approach

A laparoscopic approach follows the same oncologic principles as an open surgical procedure. Patients who have a locally advanced tumor with unquestionable radiologic signs of neighboring organ invasion generally undergo an open procedure. An open approach may be considered for certain other patients with extensive prior abdominal surgery (such as a previous cystectomy or prostatectomy), particularly for obese patients. However, obesity is very rarely an indication for open surgery in women. In men with a body mass index greater than 40, an initial laparoscopy is performed and a final decision is made about whether to proceed laparoscopically. It is very challenging to perform laparoscopic procedures for men with a body mass index greater than 50.

Should a Stapled or Hand-Sewn Restorative Procedure Be Performed?

For rectal cancers with an inferior border more than 5 cm from the anal verge, low anterior resection (LAR) and primary anastomosis generally can be used. Anastomosis also may be suitable for patients with lower tumors, depending on the distance between the distal part of the tumor and the dentate line using the preradiation measurement. If the tumor is within 2 cm of the dentate line, a stapled anastomosis is generally not possible, particularly in obese males who may have a long anal canal and in whom it is difficult to place a transverse stapler close to the dentate line. For these lesions, a transanal intersphincteric dissection is performed with a hand-sewn anastomosis. Abdominoperineal resection of the anus and rectum is indicated in patients with preexisting or likely postoperative incontinence or invasion of the anal sphincters or the pelvic floor. When the pelvic floor is invaded, an extralevator dissection is routinely performed. Inexperience with low rectal dissection, intersphincteric dissection, and hand-sewn anastomosis, or with radical perineal dissection, is an indication for referral of the patient to a surgeon and hospital with the necessary expertise.

Surgical Principles

Total Mesorectal Excision

TME is performed by sharp dissection within the plane that separates the visceral from the parietal layers of the perirectal pelvic fascia, enabling radical removal of the rectum with its surrounding mesorectum intact. The intent of TME is to remove completely the mesenteric lymph nodes and any nodules of cancer that are present within the mesorectum but are contained by the fascia propria. TME is based on embryology and anatomy and the concept that cancer spread will stay confined within the embryologic mesorectal envelope during most stages of the disease. TME achieves a radical resection along avascular planes without compromising bladder or sexual function. If the tumor approaches or breaches the mesorectal fascia, neoadjuvant chemoradiation is indicated, and the resection should include the affected neighboring organs where possible, which may mean taking nerves, ureters, the bladder, the prostate, the uterus or vagina, and, in very rare cases, even the sacrum or iliac vessels. The goal is complete removal with negative margins.

Ligation of the Inferior Mesenteric Artery

The level of ligation of the IMA has been debated. A recent international survey showed that 69% of rectal cancer surgeons perform high ligation of the IMA. Some evidence indicates that a high ligation of the IMA improves overall survival. We perform a high ligation of the IMA (proximal to the left colic artery), resulting in a D3 lymph node dissection. A high ligation of the IMA is important in achieving a tension-free, well-vascularized colorectal or coloanal anastomosis, because when the IMV is ligated close to the tail of the pancreas, mobility of the descending colon is improved.

Distal Resection Margins

The principal goal in surgical treatment of rectal cancer is to achieve an R0 resection. It is important that cancer-free margins be achieved both circumferentially and distally. Perforation of the tumor or of a rectal segment close to the tumor increases local recurrence threefold. Special care must be taken when dissecting in the perianal area during abdominoperineal resection (APR). When a tumor is located in the upper part of rectum, there is no need to remove the entire mesorectum, and a partial mesorectal excision can be performed. A clear 5-cm distal resection margin (of both rectum and mesorectum) is important when resecting upper and mid rectal cancers, because lymph node metastases can be found in the mesentery distal to the cancer. In persons with low rectal cancers, when the entire mesorectum is removed, a distal resection margin of 1 cm is adequate.

Choice of Anastomotic Configuration

A colorectal or coloanal anastomosis may be performed in several ways. A coloanal anastomosis can be end to end or side to end, with a 6-cm-long coloanal J pouch or a coloplasty. Creation of a J-pouch above a coloanal anastomosis will improve functional results for the first 2 years, compared with coloplasty or straight anastomosis. This option is performed for patients in whom a J pouch can both reach the pelvis and can fit. Although a side-to-end anastomosis is less well studied, it appears that the functional results may be equivalent to a J pouch. An end-to-end reconstruction is generally performed when the anastomosis is hand sewn or a pouch or side-to-end anastomosis will not fit.

Drainage

Whether routine drainage of the pelvis reduces the frequency of anastomotic leakage after LAR is unclear. We do not routinely use drains.

Diverting Stoma

A diverting ileostomy helps reduce the clinical manifestations of anastomotic leak. Moreover, in two recent meta-analyses, a diverting stoma was shown to reduce the frequency of anastomotic leakage and the need for a second surgery. We recommend use of a diverting stoma when the anastomosis is lower than 7 cm from the anal verge, in very elderly or frail patients who might not tolerate a leak, and in patients who have undergone preoperative chemoradiation. We perform diversion with a loop ileostomy, which is used as the specimen extraction site in laparoscopic cases.

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