【资源】全直肠系膜切除术的概念（摘自癌肿瘤学原理与实践第六版）

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The mesentery of the rectum contains its blood supply and lymphatics in a bilobed fat packet situated immediately posterior and lateral to the thick-walled rectum. Both are contained in the visceral layer of the endopelvic fascia. The majority of resectable primary rectal tumors and involved lymph nodes in rectal cancer specimens are found within this structure. Nodes are involved in T1 cancers in 5.7% of cases; T2 tumors have positive nodes in 19.6%, and T3 and T4 cancers have positive nodes in 65% and 78% of cases, respectively. [ref: 38] Involvement of the radial or circumferential margin correlates with subsequent local recurrence and poor survival. [ref: 39] Resection of the mesorectum should extend farther distally than the acceptable margin for rectal wall transection (Fig. 33.8_3). Because the mesorectum tapers as it proceeds distally, it is totally excised for most middle and lower rectal cancers. More proximal rectal tumors can be treated by a mesorectal excision extending 5 cm beyond the lower tumor edge. Total mesorectal excision has been associated with a high rate of anastomotic leak when used for upper rectal tumors. [ref: 40]
The work of Quirke and others (1986) has dramatically demonstrated the importance of lateral tumor spread in the local recurrence of resected rectal cancers (Table 33.8_2). Among patients with local recurrence, tumor involvement at the circumferential margin of resection has been found in 85% of cases. Because of difficulty in obtaining adequate exposure in the low pelvis and the surrounding structures, circumferential margins around rectal cancer can be highly variable and minimal. Surgical experience and surgical technique have demonstrated their key role in the prevention of local recurrence by controlled sharp dissection done with attention to these margins.[ref: 41] The mechanism for involvement of the circumferential margins can be direct spread, mesenteric implants, vascular or lymphatic invasion, or cancer-bearing lymph nodes.Up to 23% of patients can have mesorectal tumor implants aside from discrete nodes. [ref: 42] Tumor involvement of the circumferential margins of resection is frequently due to spread in the mesorectum distal to the tumor that can be violated by blunt dissection. [ref: 43] It has been implied that a positive circumferential margin after mesorectal excision is a prognostic factor for distant metastases also. [ref: 44]
Circumferential clearance of rectal tumors by total mesorectal excision has become the accepted surgical procedure for the management of most rectal cancer. Total mesorectal excision by full mobilization of the rectum along anatomic planes has been demonstrated to be effective in the surgical management of rectal cancer. [ref: 45,46] Dissection is carried out along areolar planes that allow for hemostasis, identification of important nerves, and prevention of violation of the visceral fascia investing the mesorectum. [ref: 47] This type of surgical resection for rectal cancer produces a negative surgical margin in more than 90% of resectable rectal cancers and reduces the possibility of local recurrence.

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