A thorough disease history should be obtained eliciting disease-specific symptoms, associated symptoms, and family history. Patients must also be assessed for their fitness to undergo surgery. Routine laboratory values, including carcinoembryonic antigen (CEA) levels, should also be evaluated in an attempt to identify an underlying focus of carcinoma. A full physical examination, including rigid proctoscopy, should be performed by the operating surgeon in conjunction with a digital rectal examination to determine the distance of the lesion from the anal verge and mobility and to assess its position in relation to the sphincter complex. All patients with a rectal lesion should undergo a full colonic evaluation with colonoscopy if possible before treatment to out rule any synchronous disease. Precise preoperative lesion localization is imperative for surgical planning, and the combination of physical examination with flexible and rigid proctoscopy will enable the determination of anterior or posterior location, relation to the valves of Houston, distance from the anal verge in centimeters, size, and distribution (% involvement of wall).

The majority of lesions planned for local excision will have a preoperative histological diagnosis that is benign, but up to 20 % of patients with a preoperative diagnosis of adenoma will have an invasive adenocarcinoma on final pathology. If concern exists regarding the appearance of the polyp or in certain patients with an invasive lesion that is being considered for local excision, radiological assessment is indicated.

The goal of the radiological preoperative evaluation is to identify lesions that are suitable for local excision by determining the radiological TNM stage, as defined by the American Joint Committee on Cancer based on the depth of local tumor invasion (T stage), the extent of regional lymph node involvement (N stage), and the presence of distant metastasis (M stage).

Endorectal ultrasound (ERUS) with rigid or flexible probes and MRI with either endorectal or increasingly phase array coils are the primary tumor-staging modalities of choice. It must be noted ERUS is more accurate in the determination of T stage for early lesions with over-staging of T1 tumors observed in 11 % of cases compared to 100 % of those staged with MRI [25]. Accurate detection of involved lymph nodes remains a diagnostic challenge for all imaging modalities, but is likely that MRI is superior in this setting. Thus ERUS and MRI should be considered complementary in the setting of early rectal cancer assessment. It must be noted that a biopsy or local excision of the target lesion prior to radiological assessment may lead to reactive lymphadenopathy, which may be confusing and lead to over-staging. If a preoperative diagnosis of invasive disease is made, all patients should have preoperative radiological staging to assess for metastatic disease with a CT scan of the chest, abdomen, and pelvis.

Mechanical bowel preparation should be administered preoperatively and prophylactic antibiotics given in accordance with departmental guidelines. Following informed consent, patients should be administered general endotracheal anesthesia with pharmacologic paralysis. The patient should be positioned for TAMIS in the high dorsal lithotomy position, which allows access to lesions in any location. Access to anterior lesions in fact can be extremely advantageous in lithotomy, which is facilitated by gravity (Fig. 3.2). This differs to TEM where the 30° camera is situated anteriorly within the lumen of the beveled resectoscope, necessitating the patient being positioned with the target lesion placed dependently. Following antiseptic skin preparation and appropriate draping, the transanal port is inserted and sutured in place (Fig. 3.3a, b). TAMIS devices are easy to set up and insert; the setup time for TAMIS is typically 1–3 min [11, 20]. Currently there exist five TAMIS platforms in common usage: GelPOINT Path™ (Applied Medical Inc, Rancho Santa Margarita, CA), SILS™ (Covidien, Mansfield, MA), SSL™ (Ethicon Endo-Surgery, Cincinnati, OH), TriPort™ (Olympus KeyMed, Southend, UK), and the improvised Gloveport. Currently, transanal platforms utilized for TAMIS are determined by individual surgeon preference. No comparative data in humans currently exists. It must be noted that the GelPOINT Path™ is the only access system to date custom designed for the purpose of transanal surgery and, along with Covidien SILS port, FDA approved for transanal use.

The pneumorectum is then established by using standard CO₂ insufflation with an initial pressure set at 15 mmHg and flow set at 40 mmHg per minute. Recently, new insufflators have been developed (Surgiquest Airseal, CT) which provide improved stability of pneumorectum at lower pressures in addition to dramatically reducing intraluminal smoke. A high-definition laparoscopic camera is inserted then to visualize the target lesion through any of the working ports (Fig. 3.4). A 30° or 45° camera lens is preferable for assessment of the lateral and proximal margins. Furthermore, a 5 mm camera provides more working space in the tight confines of the rectum than a 10 mm camera. Roticulating laparoscopes and even three-dimensional laparoscopic images (Olympus) can provide further enhanced visualization with less collision. Image stabilization and sufficient visualization of the working space are dependent on an experienced assistant surgeon.

A premium should be placed on the surgical technique and quality of resection; a non-fragmented specimen with negative margins has repeatedly demonstrated the lowest risk of recurrence. The lesion margin is first scored out on the mucosa using electrocautery with a 5–10 mm margin in order to maintain orientation and proper margins of resection (Fig. 3.5). Excision can be performed using standard monopolar electrocautery. Use of a spatula, pinpoint, or l-hook cautery allows precise dissection of the tumor and is cheap and reusable. The majority of practitioners utilize standard, straight laparoscopic instruments to perform excision, rather than roticulating instruments (Fig. 3.6). Energy devices can also be used with the principal advantage being hemostasis, albeit with increased costs. Handling of the tumor or polyp with graspers should be avoided and reduced to the surrounding mucosa to limit tumor fragmentation. On all lesions known to be malignant preoperatively, a full-thickness excision must be performed with the objective of obtaining a 1 cm minimum negative margin (Fig. 3.7). In contrast to the historical description of a simple full-thickness incision into perirectal fat, we support a pyramidal, volumetric excision containing an adequate specimen of perirectal fat as described by Lezoche. This assures an adequate resection with negative margins, in addition to possibly retrieving surrounding lymph nodes for pathologic sampling. Aggressive mesorectal excision, as described, should not breach the mesorectal fascia for concern of increasing the difficulty of total mesorectal excision should it become necessary.

For lesions believed to be benign, a partial-thickness or submucosal excision may be performed at the discretion of the operating surgeon. Submucosal excision is often not possible in patients with multiple prior attempts at endoscopic polypectomy given the obliteration of planes from inflammation and fibrosis. Proponents of this technique maintain that the possible increased risks of morbidity with deeper defects, as well as the low risk of significant malignancy in a clinically benign lesion, make this the preferred technique. In addition, submucosal excision leaves minimal inflammation and distortion should total mesorectal excision be required. However, lesions excised in a submucosal fashion are at risk of fragmentation during specimen extraction, and due to the high risk of a focus of invasion in large rectal adenomas, some authors advocate a full-thickness excision in all cases.

Specimen extraction should be performed at completion of resection and prior to closure to maintain specimen integrity and avoid accidental proximal migration. The majority of platforms accommodate this by allowing removal of the faceplate; however, some ports require removal of the entire device with reinsertion for closure. Irrigation of the excision bed with dilute Betadine, presumably for its tumoricidal and bactericidal effects, is a common practice; however, no evidence-based literature exists to support this technique.

Rectal wall or mucosal defects are then closed in a full-thickness manner completely with absorbable suture material. A running suture beginning in the lateral portion of the incision can be performed but is technically more challenging. The use of a V-Loc™ suture (Covidien, Mansfield, MA) can facilitate continuous closure by maintaining tension and negating the need for knot tying. Conversely, closure can be performed in an interrupted fashion with knot tying facilitated by laparoscopic knot pushers. The use of modern suturing devices can significantly shorten the learning curve at the expense of increased procedural costs. Specialized silver beads with applicators were initially designed for use with the TEM system; however, several other simpler laparoscopic knot-tying devices and methods have since become available (Fig. 3.8).