Operations for Rectal Cancer: Low Anterior Resection—Open, Laparoscopic or Robotic, taTME, Coloanal Anastomosis

The management of rectal cancer has evolved over the past century. Since the first description of radical abdominoperineal resection (APR) by Miles in 1908, surgery for rectal cancer has moved toward less aggressive approaches to reduce morbidity and mortality while making sphincter preservation a priority. APR involves both abdominal and perineal dissection to remove the anorectal complex en bloc with the rectum followed by creation of a permanent end-colostomy. Although this became the oncologic approach of choice for patients with rectal cancer, APR has been well known to have a profound negative impact on patients' quality of life and body image. Fast-forwarding to 1979, the concept of total mesorectal excision (TME) in conjunction with rectal resection, was introduced by Heald et al. and ultimately became the standard of care, with or without neoadjuvant treatment. TME involves precise and sharp, rather than blunt, dissection in the avascular areolar plane surrounding the mesorectum with removal of the specimen as a whole while preserving the inferior hypogastric nerve plexuses. Adoption of the surgical principles of TME led to a decrease in local recurrence rates from 20% to 45% prior to the 1990s, to 5% to 10% in more contemporary series. These results also reflect the impact of neoadjuvant treatment, which has been demonstrated to markedly lower local recurrence in rectal cancer in multiple randomized controlled trials (RCTs). Because of the substantial downstaging effect that can be achieved with current neoadjuvant therapies, sphincter preservation can be achieved in a large proportion of patients with low rectal cancers with acceptable oncologic and functional outcomes. The introduction of laparoscopy in the 1990s with advances in surgical technique and instrumentation further improved outcomes of rectal surgery by minimizing surgical trauma as reflected by reduced hospital length of stay (LOS) and recovery time while providing equivalent short- and long-term oncologic results.

In an effort to further improve maneuverability and visualization during minimally invasive pelvic surgery, robotic-assisted surgery was introduced, which has lagged in adoption by colorectal surgeons relative to other urologic and gynecologic applications. Compared to laparoscopy, the robot provides a stable camera platform, enhanced 3D visualization of the pelvic anatomy, and additional degrees of freedom to facilitate fine, tremor-free dissection. Despite these benefits and the well-demonstrated ergonomic advantages of the robotic platform, global adoption of robotics in colorectal surgery has been limited by prohibitively high costs of the platform, especially in light of the lack of evidence supporting clinical benefits relative to laparoscopic surgery.

Most recently, the growing interest in natural orifice transluminal surgery (NOTES) has facilitated the development of transanal natural orifice and minimally invasive surgery. Local transanal excision has played an important role in the management of early rectal cancer, and innovations have included development of the rigid multiport transanal endoscopic microsurgery (TEM) platform by Buess et al. in 1983 (Richard Wolf, Vernon Hills, IL), followed by the transanal endoscopic operation (TEO) system (Karl Storz, Tuttlingen, Germany). Most recently, adoption of transanal endoscopic surgery (TES) has been accelerated by the development of disposable transanal endoscopic platforms, namely transanal minimally invasive surgery (TAMIS) platforms in 2010. Through the use of adapted multiport transanal platforms and standard laparoscopic instrumentation, submucosal excision of benign rectal lesions and full-thickness excision of low-risk early-stage rectal tumors can be performed with low morbidity and acceptable local recurrence rates in carefully selected cases with no high-risk histopathologic features. In parallel to the evolution of local excision techniques for early rectal cancer, further developments in traditional proctectomy have set the stage for the most recent evolution in TME, namely transanal TME. The transabdominal and transanal (TATA) approach described by Marks et al. in 1984 combined a limited transanal intersphincteric resection (ISR) to complete the abdominal TME and facilitate sphincter-preserving proctectomy for low-lying rectal cancer. Further advances took advantage of the superior transanal endoscopic access provided by TEM to perform the entire TME using a transanal approach, a technique subsequently called taTME. The feasibility and reproducibility of this approach was demonstrated first in swine survival experiments and then in human cadaver series. This hybrid transabdominal and transanal approach to complete a radical proctectomy offers technical advantages beyond the ability to remove the specimen transanally. Transanal rectal and mesorectal dissection is greatly facilitated by CO ₂ insufflation and direct endoscopic visualization provided by transanal endoscopic platforms, which permits accurate identification of the distal resection margin and exposure of perirectal dissection planes, greatly facilitating completion of TME, particularly for low tumors in patients with a narrow pelvis, significant visceral obesity, and when sphincter preservation is intended.

This chapter reviews the various surgical approaches for the curative resection of rectal cancer, including the different techniques for completing a proctectomy with sphincter preservation. Open low anterior resection (LAR), laparoscopic LAR, robotic LAR, and laparoscopic-assisted taTME are reviewed. The benefits and limitations of each surgical approach are reviewed, as well as postoperative complications and oncologic and functional outcomes.

Anatomic Highlights

A thorough understanding of the anatomy of the colon, rectum, and pelvis is essential when performing surgery for rectal cancer regardless of the technique. The goal is to achieve adequate oncologic resection to reduce the risk of recurrence and minimize intraoperative complications, including pelvic autonomic nerve injury, to expedite recovery and provide the best quality of life with respect to urinary, sexual, and defecatory function. Mastery of pelvic anatomy allows the surgeon to recognize key anatomic landmarks and understand the pitfalls inherent in each step performed during rectal cancer surgery. Of particular importance in these procedures is the understanding of fascial planes, pelvic nerve plexuses, and their relationship to the surgical planes of dissection. To preserve sexual and bladder function after TME, it is important to identify the pelvic autonomic plexus and neurovascular bundles and avoid inadvertent injury during deep pelvic dissection.

The rectum is located along the curved sacrum and is approximately 12 to 15 cm in length. The ischial tuberosities and iliac wings form the boundaries of the pelvic cavity forming a very narrow and deep space, especially at the level of the anorectal junction. The mesorectum of the distal rectum starts to thin out and is almost absent starting approximately 2 cm above the levator ani muscles, where only the rectal wall remains. The rectum and the mesorectum are encased in the embryologically derived endopelvic fascia. The mesorectum is enveloped by the proper rectal fascia, which is separate from the parietal presacral fascia or Waldeyer fascia. This fascia is dorsal to the hypogastric nerves and ventral to the presacral venous plexus and pelvic splanchnic nerves. The prehypogastric nerve fascia can be identified between them. The Denonvilliers fascia is present between the anterior surface of the mesorectum and the prostate or vagina.

The superior hypogastric plexus located around the inferior mesenteric artery (IMA) descends along the sacral promontory and bifurcates into the hypogastric nerves. The paired hypogastric nerves run 1 to 2 cm medial to the ureters and enter the pelvis by crossing the common iliac arteries at the level of the sacrum. They then run along the posterolateral wall of the pelvis. The superior hypogastric plexus may be damaged during lymph node dissection or high ligation of the IMA at its origin. The hypogastric nerves are also at risk of being injured during mobilization of the rectosigmoid colon from the gonadal vessels and ureters or during posterior dissection of the mesorectum. Injury may lead to urinary incontinence, retrograde ejaculation in men, and decreased orgasmic intensity in women. The pelvic (inferior hypogastric) plexus extends inferiorly as a mesh composed of the hypogastric and pelvic splanchnic nerves at the lateral pelvic wall. The neurovascular bundles descend to the urogenital organ at the lateral corner of the seminal vesicle in the 10 and 2 o'clock directions. Its damage may lead to voiding, erection, ejaculation, or lubrication dysfunction.

The cavernous nerve is included within the neurovascular bundles and runs through the prostate surface of the Denonvilliers fascia and continues to the periprostatic plexus. This nerve provides parasympathetic innervation to the prostate, seminal vesicles, cavernous bodies, and the last portion of the vas deferens. Injury of these bundles results in sexual dysfunction with disturbances in erection, ejaculation, and/or vaginal lubrication.

Preoperative Staging

Accurate preoperative staging is essential when planning the most appropriate treatment for rectal cancer. A complete medical and surgical history is obtained with assessment of performance status as well as baseline urinary, sexual, and defecatory function. A comprehensive physical examination is performed including digital rectal exam (DRE). For low rectal tumors, DRE helps determine tumor location and extent along the rectal wall, relationship to the anal sphincters and anorectal ring, fixity, and sphincter tone and squeeze. A complete colonoscopy with biopsies is required for tissue diagnosis, as well as rigid proctoscopy to determine the exact location and distance of the tumor from the anal verge. Laboratory studies include a complete blood count, serum chemistries, liver function tests, and baseline serum carcinoembryonic antigen level.

Radiologic tumor staging includes computed tomography (CT) scans of the chest, abdomen, and pelvis to rule out distant metastases and magnetic resonance imaging (MRI) of the pelvis with or without endorectal ultrasound (ERUS) to evaluate the local extent of the neoplasm. Preoperative MRI has a sensitivity of 0.97 (95% confidence interval [CI], 0.96 to 0.98) and specificity of 0.97 (95% CI, 0.96 to 0.98) for determining invasion into the muscularis propria and adjacent organs, and therefore has a relatively high diagnostic accuracy for preoperative T staging and assessment of the circumferential radial margin (CRM). All radiologic imaging modalities are fraught with relatively low sensitivity with respect to lymph node assessment. Relative to ERUS, pelvic MRI is more accurate in its ability to detect lymph node involvement as it is able to view the entire mesorectum and pelvic sidewall.

For early rectal tumors and/or malignant polyps that may be eligible for local excision, ERUS is the most accurate imaging modality to confirm T1 staging given its superior resolution and definition of infiltration depth. That being said, modern MRI can assess depth of spread accurately to within 1 mm of histopathology assessments.

Neoadjuvant Treatment

Exact tumor location and accurate preoperative lymph node staging play a crucial role in preoperative and surgical planning. Rectal cancers located in the upper third of the rectum are typically treated like rectosigmoid tumors and are exempt from neoadjuvant treatment. Standard treatment of clinical stage II and III mid and lower rectal cancer includes neoadjuvant treatment with either long-course chemoradiation therapy (CRT) or preoperative short-course radiotherapy (SCRT), which not only reduces local recurrence rates relative to radical surgery alone, but also downstages a substantial proportion of tumors, potentially enabling sphincter preservation for very low rectal tumors. Long-course CRT, with 5-fluorouracil-based chemotherapy and concomitant 50.4 Gy of radiation delivered over 5 weeks can achieve up to 20% rates of complete pathologic response. Radical resection with TME is typically performed 6 to 12 weeks after completion of CRT, which allows for additional downstaging of chemosensitive tumors. SCRT can be used as an alternative to long-course CRT when chemotherapy cannot be administered or in special situations such as resectable synchronous metastases or synchronous tumors in the colon. TME is typically performed 1 week after completion of SCRT.

It is important to note that pelvic radiation is associated with significant deleterious long-term effects on anorectal, urinary, and sexual function. In addition, radiation is associated with increased rates of cardiovascular disease, pelvic fractures, and increased risk of secondary malignancies 10 years after radiation. Therefore, the potential benefits of preoperative radiotherapy in reducing local recurrence rates need to be weighed against the risks of increased long-term morbidity when determining the appropriate treatment for patients with rectal cancer.

In an effort to avoid overtreatment of low-risk rectal tumors with neoadjuvant treatment, more recent recommendations are based on improved prognostication of rectal tumors using high-resolution MRI. Currently, it is increasingly recommended that the use of CRT and SCRT be limited to rectal tumors deemed at high risk for local recurrence based on staging by pelvic MRI, including cT3b-d tumors located less than 1 mm from the mesorectal fascia, cT4 and cN1 tumors, and tumors with evidence of extramural vascular invasion (EMVI) or infiltration of the internal or external sphincter or intersphincteric space. On the other hand, tumors deemed at low risk for local recurrence based on staging MRI including cT2/T3a, cN0, and with no evidence of infiltration of the internal sphincter, should proceed directly to radical resection without administration of neoadjuvant treatment. These most recent recommendations rely on high-quality surgical resection being achieved, namely a complete TME with negative margins and CRM. TME specimen quality is critical with the majority of local recurrences reflecting inadequate mesorectal resection.

Preoperative Preparation

Preoperative preparation of rectal cancer patients who commonly present with chronic cardiovascular or respiratory conditions includes a comprehensive medical assessment and “prehabilitation” when possible to improve baseline performance status and optimize postoperative outcomes. Prehabilitation is a multimodal strategy that includes a nutritional assessment, control of anemia, and an adapted program of exercises to improve the patient's cardiologic and respiratory function. Fertility options should be discussed with patients of childbearing age. Patients in whom a permanent or temporary stoma is planned should be evaluated by an enterostomal therapist for preoperative teaching and stoma site marking.

On the day prior to surgery, patients undergo oral mechanical bowel preparation and many practitioners also routinely administer several doses of oral antibiotics (metronidazole and neomycin or erythromycin). This is based on a recent analysis of the 2012 Colectomy-Targeted American College of Surgeons National Surgical Quality Improvement Program (ACS NSQIP) database, where a decrease in the rate of surgical site infections, anastomotic leakage, and procedure-related hospital readmissions were demonstrated in patients who received combined mechanical and oral antibiotic preparation relative to patients who received no preoperative preparation or patients who received either mechanical or oral antibiotic preparation alone. Many practitioners also supplement mechanical bowel preparation with enemas to maximize clearance of the rectosigmoid and facilitate transanal access for tumor identification, rectal transection, and colorectal anastomosis.

If open surgery is planned or if conversion to open surgery is likely, epidural anesthesia is planned for improved pain control. Parenteral prophylactic antibiotics are administered prior to surgical incision as per routine, usually a second-generation cephalosporin, metronidazole, or clindamycin with a cephalosporin, ciprofloxacin or gentamicin, based on preference or allergy to penicillin or depending on patients' allergies and/or sensitivities. Other perioperative preventive measures against surgical site infection include tight glucose control in diabetics, hair removal using clippers, and maintenance of normothermia and adequate oxygenation during anesthesia. Deep venous thromboembolic prophylaxis with unfractionated heparin or low-molecular-weight heparin should be administered starting prior to surgical incision. In addition to standard prepping of the abdomen and perineum, the rectum is typically irrigated with a 1% dilute iodine solution.

Postoperatively, enhanced recovery protocols are usually followed that include early mobilization, transition to oral pain control, and resumption of oral food intake. The Foley catheter is typically removed 48 hours postoperatively, taking into account a higher risk of urinary retention in male patients with benign prostatic hyperplasia. Patients are discharged when tolerating an oral diet with resumption of bowel function, when adequate pain control with an oral regimen is achieved, and when short-term complications have been ruled out or resolved.

Surgical Management of Rectal Cancer

The oncologic principles guiding completion of radical proctectomy for rectal cancer, whether performed open or using a minimally invasive approach, are highlighted in the original description of TME. Dissection of the areolar plane surrounding the visceral fascia that envelops the rectum and mesorectum should be carried out sharply, which maximizes the likelihood of obtaining a negative CRM and mitigates the chance for local recurrence. Identification and preservation of the autonomic nerve plexuses that control urinary and sexual function should be ensured to preserve function and quality of life. Preservation of the anal sphincter and pelvic floor with restoration of gastrointestinal continuity should be applied when oncologically feasible, in highly motivated patients with realistic expectations regarding short- and long-term postoperative defecatory function and fecal continence. The various approaches to TME will be reviewed including the detailed surgical techniques, benefits and limitations, complications, and functional and oncologic outcomes.

Open Low Anterior Resection

Surgical Technique

Operative Setup

Regardless of the approach, LAR and APR require patients to be positioned in a Lloyd Davis position with the legs carefully padded in stirrups, both arms tucked at the side, and with the patient secured carefully to the operating table to minimize sliding while in steep Trendelenburg position or extreme lateral tilt. In case of APR for low rectal tumors abutting the dentate line, or when ISR with partial or complete resection of the internal anal sphincter is planned, a transanal setup is needed including a transanal scrub technician, transanal instrumentation with anorectal tray, anoscopes, a Lone Star retractor (Cooper Surgical, Trumbull, Connecticut), a headlight, and either absorbable sutures or a circular end-to-end anastomosis (EEA) stapler depending on how the coloanal anastomosis is completed. Of note, an indocyanine green (ICG) fluorescence imaging system may be used to assess vascular perfusion prior to proximal colon transection, prior to completion of colorectal anastomoses, and/or following anastomoses. Open LAR requires an adequate set of abdominal and pelvic retractors, a headlight, and a long instrument tray.

Procedural Steps

Open LAR is performed through a vertical midline laparotomy incision followed by abdominal exploration to rule out peritoneal disease and liver metastasis, vascular mobilization, mesenteric dissection, TME, rectal transection, colon resection, and colorectal or coloanal reconstruction.

After completing abdominal exploration, the patient is positioned in Trendelenburg with the right side down. The small bowel is carefully retracted out of the pelvis and to the right. A lateral-to-medial approach is used to mobilize the rectosigmoid colon. Mobilization proceeds along the white line of Toldt to mobilize the left colon and sigmoid colon. The left gonadal vessels and ureter are identified as they cross the pelvic brim and travel downward into the pelvis. The peritoneum overlying the left common iliac artery is incised and this peritoneal incision is extended further into the pelvis until reaching the avascular plane between the rectosigmoid mesentery and retroperitoneum. At this point, dissection should not proceed further and attention is returned to the proximal left colon. The lateral attachments of the proximal left colon are divided heading up toward the splenic flexure, which is then mobilized. This is followed by high ligation of the IMA, below the origin of the left colic artery. This part of the operation can also be performed using a medial-to-lateral approach, first by scoring the peritoneum at the base of the sigmoid mesentery, just above the sacral promontory, and extending this incision to the right and toward the right posterolateral region of the pelvis, with high ligation of the IMA near its origin. Dissection then moves toward the lateral attachments of the left colon, which are divided as they head up toward the splenic flexure. Pelvic dissection of the rectum is then carried out anteriorly toward the peritoneum overlying the pouch of Douglas in women and the Denonvilliers fascia in men. Anterior dissection is carried out with visualization of the seminal vesicles and prostate in men or the posterior wall of the vagina in women. Posteriorly, dissection is carried out along the plane between the Waldeyer fascia and the mesorectal fascia, with care to preserve the integrity of the mesorectum according to the principles of a TME.

In the case of a low or ultra LAR, posterior dissection between the mesorectal fascia and Waldeyer fascia is extended down toward the levators. Care should be taken to avoid injury to the pelvic autonomic nerves, specifically the superior hypogastric nerves, as they enter into the pelvis above the sacral promontory and the nervi erigentes as they travel along the pelvic sidewalls to join the inferior hypogastric plexus forming the pelvic plexus. With innervation to the prostate, genitalia, and bladder, injury to these structures may lead to erectile and urinary dysfunction.

Following complete TME with mobilization of the rectum and mesorectum well below the level of the tumor, the rectum is clamped below the tumor with a distal margin 2 cm or greater when possible, although a distal margin 0.5 cm or greater following chemoradiation is deemed oncologically acceptable. The rectum is then transected, and either a stapled colorectal or handsewn anastomosis is performed based on the level of rectal transection. A diverting loop ileostomy is often performed depending on the height of the anastomosis and whether the patient was treated with radiation preoperatively. The various types of coloanal reconstruction are reviewed in the laparoscopic LAR section of this chapter.

Benefits and Limitations

The oncologic goals of radical resection for rectal cancer are to achieve cure and to minimize locoregional recurrence. Wide adoption of the TME principles and technique has resulted in significant reduction in local recurrence rates. However, achievement of good-quality TME is not only dependent on adequate training and technical expertise of the surgeons, but also depends on tumor- and body habitus-related factors. The adequacy of the TME can be complicated by unfavorable anatomy and tumor-related factors such as low rectal tumors in a deep and narrow male pelvis with significant visceral obesity. This scenario often presents as an insurmountable obstacle to achieving adequate exposure to perform a complete rectal and mesorectal dissection under direct vision, preserve the anal sphincters, and secure adequate distal and radial margins. Deep pelvic dissection is particularly challenging when carried out down to the levators, where visualization of the distal-most portion of the rectum is severely hindered. This difficulty is reflected in the traditionally high reported rates of APR for rectal cancers located 5 cm or less from the anal verge, ranging from 7% to 27%. In addition, open LAR procedures are associated with significant morbidity including relatively high incidence of wound-related complications such as wound infection, incisional pain, prolonged LOS and recovery, and incisional hernia. It is not surprising that the adoption of laparoscopy in colorectal surgery was driven by efforts to reduce morbidity and mortality. Although adoption of laparoscopy for rectal cancer resection was delayed due to the steep learning curve and concerns over oncologic safety relative to the open approach, laparoscopy has helped overcome some of the limitations of open surgery, specifically by improving exposure of the narrow male pelvis, in patients with visceral obesity and high body mass index (BMI).

Laparoscopic, Hand-Assisted, and Single Port Low Anterior Resection

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