The anatomical basis of total rectal mesorectal excision The rectum above the peritoneal fold is covered by the peritoneum, while the rectum below the peritoneal fold is not covered by the peritoneum but by the dirty layer of the pelvic fascia. In the past, it was thought that the rectum did not have a mesentery, but anatomical studies now suggest that the structure formed by the fascial layer of the pelvic fascia wrapping around the rectum is the rectal mesentery (called mesorectum in English). The rectal mesentery is rich in lymph, blood vessels and adipose tissue, and this is the earliest place where rectal cancer invades and metastasizes. The genital ducts, internal iliac vessels, pelvic autonomic nerves, etc. in the pelvic cavity are covered and protected by the pelvic fascia wall layer, and there is a non-vascular loose gap between the pelvic fascia dirty layer and the wall layer, which is the anatomical basis of the total mesorectal excision (TME) technique. On the other hand, it maintains the integrity of the pelvic fascial wall layer, avoids pelvic nerve damage, and ensures that sexual and urinary functions are not damaged after surgery. The surgical points of total rectal mesenteric resection technique include the following: (1) sharp separation in the anterior sacral space under direct vision; (2) keeping the pelvic fascia layer intact and unbroken; (3) resection of the distal rectal mesentery of the tumor should not be less than 5 cm; the sigmoid colon should be freed first, and the submesenteric vessels should be dissected out, and the aorta and splenic vein should be 1 cm away respectively. The submesenteric arteries and veins were ligated, and the lymph nodes were cleared. The rectal mesentery was then completely freed under direct vision with scissors or electric knife along the pelvic fascia between the dirty layer and the wall layer up to the level of the anal raphe, keeping the integrity of the dirty layer of fascia. The lateral rectal ligaments are sharply separated close to the pelvic wall when dealing with them, and clamp ligation is avoided as much as possible, which can protect the autonomic plexus and maintain postoperative sexual and urinary function. Advantages of total rectal mesenteric resection technique Traditional surgery usually separates the rectum bluntly, which bleeds more and also tends to tear the rectal mesentery, leading to tumor residue or tumor dissemination, and it focuses only on the distance of the rectal cutting edge from the tumor (Figure 1).TME emphasizes the separation of the rectal mesentery under direct vision using scissors or electric knife, along the avascular zone between the dirty layer of pelvic fascia and the wall layer around the rectal mesentery, and emphasizes the circumferential peeling of the rectal mesentery until all of the distal end of the tumor is removed free of rectal mesentery or rectal mesentery up to 5 cm (Figure 2). TME routinely sharply separates the lateral rectal ligaments, avoiding the traditional surgery of clamping, cutting and ligating, which is conducive to the protection of sexual and urinary function after surgery. Figure-1. Schematic diagram of the extent of conventional rectal cancer surgery: The distal rectal mesenteric resection is small and cannot achieve complete clearance of perirectal lymph nodes. Figure-2. Schematic diagram of the scope of total rectal mesenteric excision (TME) radical rectal cancer surgery: complete resection of perirectal mesentery, or resection of rectal mesentery to an extent greater than 5 cm from the tumor, to achieve complete clearance of perirectal lymph nodes.