Although many surgeons consider modern imaging modalities to be the most effective means of tumor staging, the importance of a proper physical examination, including detailed digital rectal and vaginal examinations, cannot be underestimated. Through physical examination, the experienced surgeon gains valuable information regarding the extent of a tumor and its fixation to adjacent organs and/or the bony pelvis. A thorough pelvic examination may be the simplest, most direct method of determining whether or not sphincter-sparing surgery is feasible, or multivisceral resection or exenteration necessary. Complete colonoscopy should also be done to exclude synchronous primary tumors (2).

Contrast-enhanced computed tomography (CT) scanning is the imaging modality most frequently used to assess extent of tumor and/or presence of metastatic disease. Although CT scans can provide an approximate idea of tumor size, however, they do not always enable accurate differentiation of tumor margins from the surrounding viscera. Thus, because obtaining an adequate circumferential resection margin is paramount to curative resection, CT evaluation is not always adequate in the setting of locally advanced or recurrent tumors. Magnetic resonance imaging (MRI) generally provides a more accurate indication of pelvic involvement and the potential need for multivisceral resection. The superiority of MRI in predicting extra-rectal involvement in primary disease has been supported by several comparative studies (6,8,9).

Endorectal ultrasound (EUS) is another imaging tool that can be used to assess the local extent of a primary rectal tumor. Early, mobile transmural bowel lesions can be gauged quite accurately by EUS (2). However, because of its limited depth of field, EUS tends to understage larger lesions and has less accuracy in the setting of locally advanced tumors (6,10). In addition, as is true of all imaging modalities, the accuracy of EUS in staging rectal cancer after radiation therapy is markedly reduced because of the presence of post-radiation edema, inflammation, necrosis, and fibrosis. Studies indicate that the accuracy of EUS in the evaluation of T-stage after radiotherapy is only 50%, with a 40% rate of overstaging (10); EUS is of even less utility in the setting of a large pelvic recurrence.

Fluorine-18 fluorodeoxyglucose positron emission tomography (FDG-PET), a powerful, noninvasive imaging modality for depicting tumor metabolic activity, is a valuable tool in the preoperative staging of locally advanced and recurrent rectal cancer. FDG-PET can be utilized to assess changes in tumor glucose metabolism (11) and is especially accurate in identifying recurrent disease. EUS, CT, and MRI have demonstrated poor accuracy in distinguishing viable tumor from scar or inflammatory tissue. However, FDG-PET appears to play a vital role in differentiating scar and viable tumor (11).

The single-most important factor in curing rectal cancer is complete excision of the tumor with negative macroscopic and microscopic margins. Multimodality therapy, including chemoradiation, is often helpful in achieving this goal. In primary disease, preoperative chemoradiation has been shown to reduce local recurrence more effectively than postoperative therapy (12). A significant benefit of preoperative chemoradiotherapy is its potential to downsize the tumor (13), which may facilitate complete resection of locally advanced disease. Indeed, neoadjuvant chemoradiation has become standard practice in treating most locally advanced rectal cancers. Investigational approaches aimed at enhancing complete resection of advanced rectal cancer generally involve intensification of preoperative therapy. One such strategy is induction chemotherapy followed by standard chemoradiation. Chua et al. (14) reported on a phase II study of 105 poor-risk rectal cancer patients treated with induction capecitabine + oxaliplatin before receiving standard chemoradiation. “Poor-risk” was defined on MRI imaging as (a) tumor extending to within 1 mm of, or beyond, the mesorectal fascia; (b) T3 low-lying tumor at or below the levators; (c) tumor extending 5 mm or more into the perirectal fat; (d) T4 tumor. In the above-mentioned study, 93 of 97 patients eventually underwent complete negative-margin resections.

Patients with pelvic recurrence who have not previously received radiation should be considered candidates for preoperative chemoradiotherapy. Again, the goal is to downsize the recurrence in hopes of obtaining a complete negative-margin resection. In patients with history of limited radiotherapy, a modified regime may be possible. Patients who cannot undergo any additional radiation may be candidates for aggressive chemotherapy. In any case, if a patient has received preoperative chemotherapy and/or radiotherapy in the past, imaging should be done to exclude interval development of distant metastasis before subjecting that individual to radical resection re-staging.

Rectal cancer spreading beyond the mesorectal plane adheres to and invades adjacent organs: the sacrum and sacral nerves posteriorly; the vagina and uterus or seminal vesicles and prostate, the bladder anteriorly; and the ureters, autonomic nerve plexus, internal ileac lymph nodes, and vessels laterally. As discussed earlier, any operation undertaken in this setting is extensive and complex, requiring careful selection of patients and the coordinated involvement of a multidisciplinary team of specialists. The surgical objective is to achieve complete resection of tumor with negative margins. In
order to accomplish this goal, all organs involved by tumor must also be resected. At the same time, the surgical team should preserve as much healthy anatomy as possible. Extensive procedures of this nature often require surgical reconstruction.

Tumor adherent to regional anatomic structures is generally assumed to invade them; therefore, all or part of these organs must be removed en bloc with the tumor.

Focal invasion of adjacent organs, such as the seminal vesicles, vagina, bladder, ureter, or autonomic nerve plexus, and metastatic invasion of lymph nodes in the pelvic sidewall require extended rectal resection. The type of procedure—total pelvic exenteration, posterior exenteration, anterior exenteration, abdominoperineal resection (APR) with sacrectomy, sacropelvic exenteration—varies, depending on the extent of tumor spread into adjacent organs as well as the distance of tumor from the anal sphincter musculature.

Patients undergo bowel preparation the day before surgery. Placement of ureteral stents can be done preoperatively to help identify and protect the ureters. If an APR is planned, suturing of the anus will help prevent fecal contamination. Antibiotics are delivered in the operating room along with anesthesia. The patient is placed in the lithotomy position, giving the surgeon anterior access to the pelvis and the perineum. Surgery will be performed in one or two stages, depending on the type of resection.

The surgeon must first examine the abdomen for disseminated peritoneal disease and/or for tiny hepatic metastases that may not have appeared on preoperative imaging studies, as detection of these would dictate a change in management. Following abdominal inspection, the origin of the inferior mesenteric artery (at the aorta) is dissected. The surgeon must examine the retroperitoneal lymph nodes for metastasis, the presence of which might indicate incurable disease, especially if the nodes cannot be easily removed. The ureters are identified and preserved; however, these are not transected until resectability is confirmed, enabling the surgical team to monitor output of urine. The inferior mesenteric artery is ligated and transected, and the rectosigmoid is subsequently transected about 10 cm proximal to the tumor. The surgeon dissects the rectum posteriorly, down to the levator ani, taking care to avoid the pelvic nerves whenever possible. The bladder is mobilized from the retropubic space. The lateral bladder pillars attached to the lateral pubic rami are ligated and transected. In a female patient, the cardinal ligaments supporting the vagina and cervix are ligated and transected at the pelvic sidewall. In a male patient, dissection continues anteriorly and includes the prostate.

An intraoperative decision must now be made: Will the surgical team proceed with a low anterior resection, or is an APR required? If an APR proves necessary, dissection must continue below the levator ani muscles. Following this, perineal dissection begins. The anal canal and the lower rectum are dissected and removed through the ischiorectal fossa and urogenital diaphragm. If the tumor is extensively invasive, removal of a female patient’s vagina, vulva, and urethra may be required. The entire specimen may then be removed via an abdominal or perineal incision.