**3. Conclusion**

The rectum is surrounded by a fatty tissue complex called the mesorectum, which contains abundant blood vessels, lymphatics, and lymph nodes. The rectum and mesorectum are enveloped by the mesorectal fascia. During total mesorectal excision, it is important to completely excise this mesorectal fascia without damage. The mesorectal fascia conjoins with the recto-sacral fascia, which extends forward from the presacral fascia at the level of S4, and descends to the pelvic floor. To enter the retro-rectal space and reach the pelvic floor, this fascia must be incised and sharp dissection should be performed to prevent severe bleeding due to injury to the presacral plexus. During the anterior dissection of the rectum, it is important to recognize Denonvillers' fascia located between the rectum and seminal vesicles, and dissection should be performed below the Denonvilliers' fascia. The pelvic floor is a structure that forms the bottom of the pelvis and is mainly composed of the levator ani muscle complex: pubococcygeus, iliococcygeus, and puborectalis muscle. The levator ani muscle received direct innervation from sacral nerve roots (S3-S5) and play an important role in cooperative action during defecation. To reach the deep part of the anal canal, the dissection should be performed between the puborectalis muscle and the rectal wall. During the whole process of TME, surgeons should take care to identify and preserve the autonomic nerve in order to avoid postoperative urogenital dysfunction. Care should be taken not to damage the superior hypogastric nerve during IMA ligation, and not to damage the pelvic plexus during posterolateral pelvic dissection. In addition, during anterior dissection of the rectum, it is important to perform meticulous dissection so as not to injure small numerous neurovascular bundles running in the 2 o'clock and 10 o'clock directions of the seminal vesicle. Based on a sufficient understanding of pelvic anatomy, precise surgical techniques using advanced surgical tools will give favorable oncologic and functional outcomes for rectal cancer patients.
