The concept of the rectum has been internationally and nationally standardized: the rectum is a section of the large intestine 15 cm up from the anal verge. The rectum is surrounded by fat, without longitudinal bands, and is located dorsally to the bladder and genital organs. The arterial blood supply of the rectum is mainly the superior rectal artery from the inferior mesenteric artery, the middle rectal artery from the internal iliac artery and the inferior rectal artery from the internal iliac artery. However, in recent years, some scholars and oncology organizations, such as ASCO (2001 Clinical Guidelines for Colorectal Surgery), NIH, and NCI, have proposed a new concept of the rectum.