Overview

Planning for distal transection of the bowel in a patient with rectal cancer involves review of the preoperative history, digital rectal examination, endoscopy, and imaging, as well as a thorough intraoperative evaluation. Invasion of the sphincter complex by the tumor as determined before or after neoadjuvant therapy is an indication for abdominoperineal resection.[1] The surgeon should have a clear understanding of the intended margin before taking the patient to the operating room, and an adequate operative approach should be planned in the preoperative setting.

Tumors of the upper rectum and rectosigmoid junction behave more like colon cancers and should be removed with a distal margin of 5 cm after a tumor-specific (partial) mesorectal excision.[2] A partial mesorectal excision is initially performed as a total mesorectal excision (TME) with dissection starting in the avascular plane and dissecting in this plane from the superior to the inferior. After dissection is 5 cm distal to the tumor, the mesorectum is transected perpendicular to the bowel, usually just prior to the bowel transection.[3] Resection of mid and low rectum cancer generally includes the entire mesorectum; ideally, these tumors are removed with a distal margin of at least 1 cm, although shorter margins can be adequate in selected cases, depending on tumor location, size, and response to neoadjuvant therapy.[4][5]

Whether the operation is open or minimally invasive in approach, the indication to proceed with a stapled or handsewn anastomosis rests largely on the distance between the lower edge of the tumor and the anorectal ring. This measurement can usually be obtained with a simple preoperative physical and endoscopic examination. A distance of 2–3 cm between the tumor and the anorectal ring is usually necessary to allow safe stapling of the bowel below the lower level of the tumor with adequate oncologic clearance in both minimally invasive and open procedures, thereby leaving some rectal length to accommodate the stapled reconstruction. Currently, the role of transanal TME in an effort to ensure a proper distal margin is uncertain, but one clear advantage of the transanal approach is the more accurate determination of the distal transection margin in low rectal cancers. In cases of patients with obesity and/or bulky lesions, more distal clearance may be necessary, especially in male patients. Combined transabdominal and transanal intersphincteric resection followed by handsewn coloanal anastomosis is the best approach for tumors that do not invade the sphincter complex but are very close (see the first video below). In these cases, an adequate distal margin can be assessed under direct transanal visualization with partial or complete division of the internal sphincter. The decision whether to first perform the transanal or transabdominal part of the operation or to first conduct a combined procedure is at the discretion of the operating team. Similarly, the best position for the transanal approach—prone jackknife or lithotomy—depends on the experience and skill of the operators, although the prone position is especially well suited for large patients and anterior tumors.[6]

A stapled anastomosis can be constructed using a purse-string suture for the distal rectal side of the anastomosis and a single end-to-end anastomosis (EEA) stapler or a stapled distal rectal side for a double-stapled anastomosis. In a minimally invasive approach, application of an endoscopic linear stapler can be difficult on the low rectum and often requires two firings. For a mid-rectal transection, the endo-stapler is brought in from the right side dividing the rectum transversely in part and then pulling the rectum up towards the left shoulder creating a mitered cut to complete the left side of the rectal transection (see the video below). The trocar of the circular stapler is extended through the apex of the staple line (i.e., top of the inverted V) at the time of anastomosis.

Alternatively, a vertical staple line can be created by dividing the rectum from anterior to posterior with two firings of the endostapler (see the video below). It is important to accomplish the rectal transection with no more than two stapler firings because the incidence of anastomotic complications has been shown to increase when using more than two firings.[7][8] Full mobilization of the “bared” distal rectal tube by incision of the posterior and lateral aspects of Waldeyer’s fascia (rectosacral fascia) at the anorectal junction will facilitate endoscopic transection of the rectum. When two stapler firings do not complete the rectal transection, it is commonly because of incomplete release of the anorectal junction without full visualization of the anterior, lateral, and posterior views of the “bared” distal rectal tube.