Bowel Transection and Anastomosis
Planning for distal transection of the bowel in a patient with rectal cancer involves information gathered from preoperative 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. 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. Cancers of the mid and low rectum generally include the entire mesorectum and are ideally 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.,
Whether the operation is open or minimally invasive in approach, the indication to proceed with a stapled or hand-sewn 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. In cases of obese patients and/or bulky lesions, more distal clearance may be necessary, especially in male subjects. Tumors that do not invade the sphincter complex but are very close are best approached by a combined transabdominal and transanal intersphincteric resection (TATA) followed by hand-sewn coloanal anastomosis (Figure 8.1). 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 to first perform the transanal or transabdominal part of the operation, or to 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 an initial prone position is especially well suited for large patients and anterior tumors.
A stapled anastomosis can be constructed using a purse-string suture for the distal rectal side of the anastomosis and a single EEA stapler or a stapled distal rectal side for a double-stapled anastomosis. In a minimally invasive approach, application of the Endo-GIA stapler can be difficult on the low rectum and requires two firings of the endo-stapler. 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 (Figure 8.2). 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 endo-stapler (Figure 8.3). It is important to accomplish the rectal transection with not more than two stapler firings because the incidence of anastomotic complications has been shown to increase when using more than two firings., Full mobilization of the “bared” distal rectal tube by incision of the posterior and lateral aspects of Waldeyer’s 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 due to incomplete release of the anorectal junction without full visualization of anterior, lateral and posterior view of the “bared” distal rectal tube.
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