Pelvic anatomy for colorectal surgeons.

INTRODUCTION: recent advances in rectal surgery include total mesorectal excision and preservation of the autonomic pelvic nerves, so that colorectal surgeons have to get some information on the embryology of the rectum, on the complex anatomy of the pelvic floor and on the distribution of lymphatic nodes. Embryology includes the formation of the hindgut during the first month of the embryo and the subsequent formation of the rectum and anal canal. The mesorectum contains the blood vessels and the lymphatic nodes. To totally excise the mesorectum, the surgeon should follow the "holy plane" described by Heald, between the perirectal fascia and the pelvic fascia. Doing this, the surgeon has the best chance to preserve the autonomic pelvic nerves that comprise the superior hypogastric plexus, the right and left hypogastric nerves and the right and left inferior hypogastric plexuses.