**1. Introduction**

Colorectal cancer is the third most common cancer and the fourth leading cause of cancer-related deaths worldwide [1]. Especially, rectal cancer accounts for 30–40% of colorectal cancer, and the treatment strategy is different and more complicated compared to colon cancer because of its anatomical features. Although the treatment outcome of rectal cancer has greatly improved with the development of multimodality treatment including neoadjuvant radiotherapy, cytotoxic chemotherapy, and target agents, surgery remains the mainstay of therapy. Since the concept of total mesorectal excision (TME) was first described by Richard Heald in 1979, this procedure became the gold standard technique for rectal cancer surgery until now [2]. The fundamental principle of TME is en bloc resection of the rectum with its surrounding fatty tissue complex which contains the blood vessels and lymphatics down to the pelvic floor. To achieve complete TME and sphincter preserving surgery in low-lying rectal cancer, knowledge for regarding the pelvic fascia (mesorectal, parietal) and autonomic nerves, a thorough understanding of the pelvic floor anatomy is essential.
