Beyond Total Mesorectal Excision: Compartment-based Anatomy of the Pelvis Revisited for Exenterative Pelvic Surgery.

Objective: Magnetic resonance imaging-based subdivision of the pelvis into 7 compartments has been proposed for pelvic exenteration. The aim of the present anatomical study was to describe the topographic anatomy of these compartments and define relevant landmarks and surgical dissection planes.

Background: Pelvic anatomy as it relates to exenterative surgery is complex. Demonstration of the topographic peculiarities of the pelvis based on the operative situs is hindered by the inaccessibility of the small pelvis and the tumor bulk itself.

Materials And Methods: Thirteen formalin-fixed pelvic specimens were meticulously dissected according to predefined pelvic compartments. Pelvic exenteration was simulated and illustrated in a stepwise manner. Different access routes were used for optimal demonstration of the regions of interest.

Results: All the 7 compartments (peritoneal reflection, anterior above peritoneal reflection, anterior below peritoneal reflection, central, posterior, lateral, inferior) were investigated systematically. The topography of the pelvic fasciae and ligaments; vessels and nerves of the bladder, prostate, uterus, and vagina; the internal iliac artery and vein; the course of the ureter, somatic (obturator nerve, sacral plexus), and autonomic pelvic nerves (inferior hypogastric plexus); pelvic sidewall and floor, ischioanal fossa; and relevant structures for sacrectomy were demonstrated.

Conclusions: A systematic approach to pelvic anatomy according to the 7 magnetic resonance imaging-defined compartments clearly revealed crucial anatomical landmarks and key structures facilitating pelvic exenterative surgery. Compartment-based pelvic anatomy proved to be a sound concept for beyond TME surgery and provides a basis for tailored resection procedures.