Hyaehwan Kim
Martin R. Weiser
Presentation
A 62-year-old male presents to his primary care provider with complaints of bright red blood per rectum and thin-caliber stools for the past 2 months. His past medical history includes mild hypertension and hypercholesterolemia, and his current medications include Lopressor 25 mg daily, Lipitor 40 mg daily, and aspirin 81 mg daily. The patient denies any allergies. He had a right inguinal hernia repair at age 35. He quit smoking more than 20 years ago and drinks alcohol occasionally. His father died of complications related to a ruptured abdominal aortic aneurysm at the age of 80, and his mother was diagnosed with early-stage breast cancer at age 70. The patient has never had a colonoscopy. Digital rectal exam (DRE) in the primary care physician’s office reveals a rectal mass, with gross blood on the examining finger. Serum laboratory studies show hemoglobin of 9.5 g/dL.
Differential Diagnosis
Although rectal bleeding and changes in bowel pattern can be associated with many benign conditions, rectal cancer is obviously the most likely diagnosis when an associated mass is identified on digital rectal examination. This is especially true of patients who present in the sixth or the seventh decade of life.
Workup
The patient is referred for colonoscopy, which was complete to the cecum. A 4-cm nonobstructing mass is noted in the rectum and biopsied. Additionally, a 1-cm transverse colon pedunculated polyp is completely removed. Pathology reveals an invasive, moderately differentiated adenocarcinoma of the rectum and an adenoma of the transverse colon. The patient undergoes a computerized tomography (CT) scan of the chest, abdomen, and pelvis with oral and intravenous contrast, which reveals a 2-mm nonspecific right upper lung nodule, a rectal mass consistent with the primary cancer, and no evidence of liver metastasis. Carcinoembryonic antigen (CEA) is within the normal range.
The patient is referred to a colorectal surgeon. On examination, DRE reveals the rectal mass to be tethered, but not fixed, and located 2 cm above the anorectal ring (i.e., 2 cm above the top of the external sphincter complex). On rigid proctoscopy, the lesion is 7 cm from the anal verge in the anterior position. It is ulcerated and occupies 40% of the bowel circumference. Endorectal ultrasound (ERUS) is performed and demonstrates that the rectal lesion extends to the muscularis propria and into the perirectal fat (uT3). There are two hypoechoic nodules in the mesorectum, adjacent to the tumor, measuring 4 and 5 mm, respectively. These are consistent with mesorectal lymph node metastasis (uN1).
Discussion
Rectal cancer comprises nearly 30% of all colorectal cancers, approximately 41,000 new cases per year. Most rectal cancers present in patients in the sixth to the eighth decade of life. Synchronous adenomas and colorectal cancers are seen in 30% and 3% of cases, respectively. Thus, complete colonoscopy is necessary prior to surgery. Rectal cancer specifically refers to extraperitoneal lesions (i.e., lesions below the peritoneal reflection). Generally, these lesions are located <12 to 15 cm from the anal verge (as found on rigid proctoscopy). Lesions above the peritoneal reflection are usually treated as colon cancers.
The degree of tumor fixity in the pelvis is related to the depth of penetration of the primary lesion through the rectal wall. Mobile lesions are often limited to the mucosa, submucosa (cT1), or muscularis propria (cT2), whereas tethered lesions generally represent tumors extending into the perirectal fat or the mesorectum (cT3). Fixed tumors can extend into surrounding anatomic structures such as the prostate, seminal vesicles, or vagina (cT4). Many rectal cancer patients present without pain. However, when pain is present it indicates probable involvement of the sphincter by tumor. Tumors that are painful often extend into the external sphincter complex. ERUS (Figure 1) and phased array magnetic resonance imaging (MRI) (Figure 2) are currently the best imaging modalities for staging of rectal cancer, capable of accurately staging the primary lesion with up to 90% accuracy and locoregional lymph nodes with an accuracy of as much as 80%. ERUS is slightly better than MRI in the staging of early lesions, while MRI is preferable for staging very bulky lesions with questionable invasion into surrounding organs (T4 lesions).
FIGURE 1 • ERUS demonstrating the hypoechoic primary rectal cancer at the level of the seminal vesicles (A) and the prostate (B) with invasion into the perirectal fat. Hypoechoic mesorectal lymph node indicative of nodal metastasis (C).
FIGURE 2 • MRI demonstrating the primary rectal cancer (A) and the mesorectal adenopathy (B) on axial imaging. (C) demonstrates the tumor in the sagittal plane.
Pretreatment staging is critical to optimal patient care. Early lesions (stage I) are generally treated with surgery alone, while more advanced lesions (stages II and III) are treated with multimodality therapy including chemotherapy, radiotherapy, and surgery. Prospective randomized data have proven that chemoradiation is better tolerated and more effective if delivered preoperatively rather than postoperatively.
Rectal resection done in accordance with the proper technique of mesorectal excision is associated with local recurrence rates of <10%. Sharp dissection along the embryonic planes between the visceral and the parietal layers of the endopelvic fascia ensures complete removal of the locoregional lymph nodes in the mesorectum, preserves autonomic nerve function, and results in reduced blood loss.
Diagnosis and Treatment
In this patient, pretreatment staging indicates a uT3N1, stage III, mid-to-low rectal cancer. The patient should be treated with combined modality therapy (CMT), which most commonly includes 5 fluorouracil (5FU) administered as continuous intravenous infusion or as oral Xeloda, concomitant with 5,040 cGy delivered over the course of 25 to 28 daily fractions (Monday through Friday for 5.5 weeks). Following chemoradiation, repeat staging is done with a CT of the chest, abdomen, and pelvis (with oral and intravenous contrast). Proctoscopy is also performed to assess for interval development of distant metastasis and evaluate the response of the primary tumor to therapy. As long as extensive distant metastases have not developed, the patient should proceed to surgical resection. Preoperative counseling should include a discussion regarding the possibility of a diverting stoma. The possibility of postoperative sexual and bladder dysfunction, as well as post low anterior resection (LAR) syndrome (which includes stool frequency, urgency, and clustering) should also be discussed. It is critical for the patient to understand that postoperative bowel function may take 12 to 24 months to plateau and may be permanently altered. Preoperative marking for a colostomy or an ileostomy in the office optimizes stoma location. Although the utility of bowel preparation has been questioned in regards to surgery for colon cancer, it remains useful in rectal cancer surgery.
Surgical Approach
In the operating room, the patient is placed in a modified lithotomy position. A bladder catheter is introduced. DRE and irrigation are performed to again assess the location of the tumor and remove any remaining stool from the rectum.
A midline incision is made, extending from the pubis to just above the umbilicus. Potential stoma sites must be kept in mind. Additional cephalad extension may be necessary to mobilize the splenic flexure. The abdomen is explored to search for metastatic disease in the liver or peritoneal surfaces and the small bowel packed in the upper abdomen. The patient is placed in a slight Trendelenburg position. Proper mobilization of the sigmoid is initiated by scoring the white line of Toldt followed. The left ureter and gonadal vessels are identified. The peritoneum is scored along the superior rectal artery to the base of the inferior mesenteric artery; this helps the surgeon maintain the sympathetic autonomic nerves in the retroperitoneum. The pedicle is ligated just distal to the takeoff of the left colic pedicle. High ligation of the inferior mesenteric artery is used selectively, as in the presence of bulky nodal disease; it has not been associated with improved oncologic outcome and can result in autonomic nerve injury. The mesentery is divided up to the left colon, which is divided with a stapler. The peritoneum is then scored bilaterally into the pelvis and around the anterior peritoneal reflection. The sigmoid mesentery is raised off the retroperitoneum again, with care taken to avoid injury to the autonomic nerves. With the rectum retracted anteriorly, the avascular plane between the visceral and the parietal layers of the endopelvic fascia is developed and characterized by loose areolar tissue. Posterior dissection is facilitated by use of the St. Marks retractor. It continues sharply through Waldeyer’s fascia (rectosacral fascia that extends from S4 to the rectum/mesorectum). Blunt dissection should be avoided, as Waldeyer’s fascia can tear at the presacral fascia, causing bleeding into the mesorectum resulting in an incomplete nodal dissection.
For mid to low rectal cancers, dissection is taken to the pelvic floor. Lateral dissection is also performed sharply with cautery, adjacent to the mesorectum, to avoid injuring the parasympathetic nerves. Pelvic sidewall dissection with en bloc removal of the parietal layer of the endopelvic fascia is performed, when necessary, to ensure clear circumferential margins. The anterior dissection is often developed last. In male patients, the dissection is continued through or anterior to Denonvilliers fascia and, if possible, both layers are removed from the seminal vesicles and the upper prostate, especially in the case of anterior lesions. At this point, the distal extent of the tumor and the transaction site are established. For tumors of the upper rectum, dissection continues 5 cm below the level of the mass. The mesorectum is then divided perpendicular to the intestine, to avoid “coning.” For mid to low rectal cancers, dissection is completed to the pelvic floor, where the mesorectum ends. In the past, a 2-cm distal rectal margin has been recommended; however, numerous recent reports have shown that a 1-cm distal margin is sufficient, especially in the setting of preoperative chemoradiation. Once the distal resection line is identified, the rectum is clamped below the tumor and the distal rectum irrigated with a liter of saline to remove exfoliated cells and debris. Using a double staple technique, the rectum is stapled and divided with a linear stapler and the specimen is tagged and removed from the field.
The left colon, or occasionally the sigmoid (if it is supple and well vascularized), is used for reconstruction. Splenic flexure mobilization is often required. Additional maneuvers for obtaining length include dividing the inferior mesenteric vein adjacent to the ligament of Treitz and dividing the inferior mesenteric artery.
A circular stapler is then chosen, and the anvil placed within the opened bowel with purse-string stitch. After verification of hemostasis, the anvil is brought down to the stapler and connected; the staple is closed and anastomosis created (second staple line). After opening the staples, the tissues from the proximal and distal bowels are inspected to ensure that the two rings of tissue (donuts) are intact. Further verification of intact anastomosis is performed by proctoscopy, and while the rectum is insufflated the pelvis is filled with saline to assess for leakage of air.
Special Intraoperative Considerations
Patients with obstructing lesions may require colonic stenting or colostomy prior to beginning chemoradiation. The decision to intervene surgically before starting chemoradiation depends on the patient’s symptoms as well as clinical examination. If an adult colonoscopy can be passed above the lesion, chemoradiation is often tolerated without further intervention.
For a very low anastomosis (<6 cm from the anal verge), a colonic J-pouch should be considered because it will improve bowel function in the short term. Limitations include a narrow pelvis or a descending colon of limited length.
For patients with bulky tumors and possible extension of tumor into surrounding structures (small intestine, ovary, bladder, vagina, prostate or seminal vesicle), en bloc resection should be performed. It is often not possible to identify a malignant fistula from a benign adhesion. Mere division, or “pinching,” of tumor is not an acceptable surgical technique, as it may reduce the chance of cure.
Following creation of an anastomosis, an air leak test is performed to search for incomplete stapling. If the air leak test is positive, the anastomosis should be carefully evaluated by proctoscopy. Anastomotic takedown should be considered if large anastomotic defects are noted. Small defects can be repaired with sutures. In some situations, the leak is small and cannot be identified. In these situations, a diverting stoma should be strongly considered.
Postoperative Management
Nasogastric tubes are not routinely utilized postoperatively. Early mobilization and feeding can reduce ileus and hospital length of stay. Foley catheters are left in place for 4 to 5 days, as urinary retention (due to nerve edema associated with low dissection) can occur with early catheter removal. Anastomotic leak occurs in as many as 20% of patients and usually presents with fever, tachycardia, arrhythmia, tachypnea, or diffuse peritonitis within 4 to 7 days postoperatively. The incidence is higher in anastomoses within 7 cm from the anal verge, and in patients who have received antiangiogenic agent therapy (i.e., bevacizumab). Fecal diversion is commonly utilized in order to avoid the potential sequelae of an anastomotic leak. A meta-analysis study by Tan et al. evaluated data from four randomized controlled trials and 21 nonrandomized studies (N = 11,429). They observed that lower clinical anastomotic leak rate (risk ratio [RR] = 0.39 and 0.74) and a lower reoperation rate (RR = 0.29 and 0.23) was associated with use of a diverting stoma in both randomized control trials and nonrandomized studies. Temporary fecal diversion should be considered in those patients thought to be at high risk for leak.
Long-term complications include sexual and bladder dysfunction associated with pelvic sidewall dissection, preoperative chemoradiation and abdominoperineal resection. Most patients opt for sphincter-sparing LAR over a permanent stoma. However, the rate of incontinence following LAR is reportedly as high as 60%, and patients must be counseled thoroughly regarding their options and the likely outcomes.
While preoperative CMT has been found to be beneficial, the role of adjuvant chemotherapy is not as clear. Randomized trials to determine the necessity of postoperative adjuvant chemotherapy are not available; thus, adjuvant chemotherapy currently remains the standard of care in the United States for Stage III rectal cancer.
Long-term rectal cancer follow-up includes serum CEA and physical examination, including DRE and proctoscopy, every 3 to 6 months for 2 years and then every 6 months for an additional 3 years. CT scan of the chest, abdomen, and pelvis is performed yearly for 3 years. Colonoscopy is performed 1 year from surgery and then 3 years later if no additional polyps are seen.
TAKE HOME POINTS
· Rectal cancer often presents in asymptomatic patients in the sixth to the seventh decade of life. When it is symptomatic, bright red blood per rectum, with or without a change in bowel pattern, is most common.
· Full colonoscopy is required to rule out synchronous lesions. If this is not possible due to obstruction, virtual colonoscopy or barium enema should be considered. Otherwise, colonoscopy within 3 months of surgery is recommended.
· Rectal cancer workup includes CT scan of the chest, abdomen, and pelvis to determine extent of disease. The primary lesions should be staged with ERUS/MRI and evaluated by proctoscopy.
· The standard of care for mid to low rectal cancer extending into the mesorectum, or involving locoregional lymph nodes, includes chemoradiation followed by mesorectal excision.
· Preoperative chemoradiation is better tolerated than postoperative treatment. It results in less local recurrence and is associated with fewer complications than postoperative treatment.
· Mesorectal excision is the standard surgical approach for mid to low rectal cancers and involves dissection along the areolar plane between the visceral and the parietal layers of the endopelvic fascia. Sharp mesorectal excision reduces rectal cancer-associated postoperative morbidity by preserving the superior and the inferior hypogastric nerve plexus.
· Postoperative complications following rectal surgery include sexual and urinary dysfunction, and anastomotic leak.
· Diverting ileostomy should be considered for low anastomosis, especially in the setting of preoperative chemoradiation.
· Serum CEA, DRE, and proctoscopy are performed every 3 to 6 months for 2 years after surgery and then every 6 months for an additional 3 years. CT scan of the chest, abdomen, and pelvis is performed annually for 3 years. Colonoscopy is performed after the first year; if no additional polyps are seen, it can subsequently be performed 3 years later.
SUGGESTED READINGS
Edelman BR, Weiser MR. Endorectal ultrasound: its role in the diagnosis and treatment of rectal cancer. Clin Colon Rectal Surg. 2008;21(3):167–177.
Fazio VW, et al. A randomized multicenter trial to compare long-term functional outcome, quality of life, and complications of surgical procedures for low rectal cancers. Ann Surg. 2007;246(3):481–488; discussion 488–490.
Minsky BD. Chemoradiation for rectal cancer: rationale, approaches, and controversies. Surg Oncol Clin N Am. 2010;19(4):803–818.
NCCN Guidelines, v. 2011 02/15/2011; Available from: http://www.nccn.org
Nelson H, et al. Guidelines 2000 for colon and rectal cancer surgery. J Natl Cancer Inst. 2001;93(8):583–596.
Sauer R, et al. Preoperative versus postoperative chemoradiotherapy for rectal cancer. N Engl J Med. 2004;351(17):1731–1740.
Weiser MR, et al. Sphincter preservation in low rectal cancer is facilitated by preoperative chemoradiation and intersphincteric dissection. Ann Surg. 2009;249(2):236–242.