The principal procedures for rectal tumors are as follows:
Low Anterior Resection
This operation, performed through an abdominal incision, is the curative procedure of choice provided a margin of 2 cm of normal bowel—as estimated at operation—can be resected below the lesion. At least 10 cm of bowel proximal to the growth should be removed along with the lymph node-bearing tissue. It is important to excise 5 cm of mesorectum distal to the tumor to minimize the chance of local recurrence from cancer in lymph nodes. The mesorectum tapers and diminishes at the level of Waldeyer’s fascia. However, this technique resulted in a high leak rate; therefore, surgeons recommend a “tumor-specific” sharp mesorectal excision preserving the mesorectal fascia integrity for at least 5 cm distal to the tumor. Widespread acceptance of this technique has resulted in a decrease in recurrence rates of rectal cancer from 20–30% to 5–10%. Controversy surrounds the fact that prior to Heald’s report, there were centers that reported very low recurrence rates for rectal cancer because they were already performing a “tumor-specific mesorectal excision” by following the natural plane of dissection when performing proctectomy. The descending or sigmoid colon is anastomosed to the rectum. This type of resection is likely to fail in patient with extensive carcinoma and local spread. The end-to-end stapling device facilitates very low anastomosis, sometimes even as low as the anal canal (coloanal anastomosis). Unfortunately, such low reconstruction is associated with functional difficulties including seepage, urgency, and frequent bowel movements. This improves over time (1–2 years). Many surgeons prefer to construct a colonic J-pouch or perform a coloplasty, when technically feasible, to diminish the severity of these symptoms in the first year.
When adequate distal margins for low anterior resection cannot be obtained, or the patient’s functional status obviates a sphincter-sparing approach, an abdominoperineal resection is performed. A permanent end colostomy is required.
Curative resections for cancer of the rectum can be carried out by laparoscopic-assisted techniques. Initial enthusiasm for laparoscopic techniques was limited due to a high incidence of port site metastases in early reports. Contemporary reports demonstrate that with proper technique, port site metastases are no longer a concern. The final results of a prospective, multi-institutional trial comparing conventional open resection with laparoscopic-assisted colectomy have just been published, and the data demonstrate patient benefits and oncologic efficacy of laparoscopic surgery for colon cancer when performed by qualified surgeons.
In patients with small, well-differentiated, superficial, mobile polypoid lesions, a disk of rectum containing the tumor can be excised as definitive therapy. This technique of resection should be limited to selected T1 lesions because patient survival with salvage radical surgery for recurrence after excision of T2 and deeper lesions may be much poorer when compared to initial radical surgery. Lymph nodes are not sampled or treated by excision, and success is based on adherence to strict criteria that predict a low likelihood of nodal spread. A strategy of chemoradiation and excision has been reported in small case series for lesions more advanced than T1; however, the long-term results are not well documented and this approach should subject to clinical trials. Transanal endoscopic microsurgery is a recently developed minimally invasive technique for the local resection, best suited for more proximal rectal lesions. The same criteria are applied to patients for conventional local excision or TEM.
Unresectable rectal cancers can be palliated by fulguration (electrocoagulation) or laser photocoagulation. Fulguration requires general anesthesia, and the laser procedure does not. Unfortunately, symptom relief—of bleeding, tenesmus, and mucus discharge—in patients with these advanced lesions is often less than anticipated. In such cases colonoscopically deployed endoluminal stents can provide relief of obstruction even when the lumen is too small to accommodate a pediatric colonoscope. Tumor ingrowth will cause stent occlusion within 6–9 months, but this can be prolonged with laser photocoagulation. The Hartmann procedure may be indicated in poor-risk patients—the bowel with its contained cancer is removed through the abdomen with permanent colostomy but without excision of the distal rectum, which is sutured closed.