Overview

A tailored mesorectal excision (also referred to as a partial mesorectal excision or tumor-specific mesorectal excision) can be employed for cancers in the upper and upper-mid rectum. The rationale for a 5-cm distal margin is based upon data showing longitudinal spread within the tubular lymphatics and lymph nodes of the mesorectum extending 2–4 cm distal to the lesion.[1][2] For upper rectal cancers, a distal mesorectal margin of 5 cm should be obtained. However, for lesions in lower-mid and distal rectum, total mesorectal excision (TME) that includes all of the mesorectum should be performed (hence, a "total" mesorectal excision). For lower cancers, after neoadjuvant therapy, a distal margin as small as 1 cm is acceptable in order to achieve sphincter preservation, with good oncologic control.[3][4][5]

TME is associated with a higher incidence of anastomotic leak due in part to devascularization of the distal rectum used to construct an anastomosis. Partial mesorectal excision lowers the risk of devascularization and remains appropriate for more proximal cancers as supported by histologic examination of the extent of lymphatic cancer spread in the mesorectum distal to the cancer.[6]

Partial mesorectal excision follows the same dissection planes as TME, with the mesorectum divided perpendicular to the axis of the rectum at the level of the distal mesorectal margin. For proximal rectal cancers, this margin should be 5 cm distal to the cancer (video). To avoid the exfoliation of viable cancer cells, some surgeons irrigate the rectal lumen with a tumoricidal agent (e.g., sterile water, Betadine solution). This procedure can be done prior to stapling and dividing the rectum.[7]