"Mesorectum": the surgical value of an anatomical approach

The quality of total extirpation of the "mesorectum" nowadays determines the prognosis of rectal cancer but the planes of surgical dissection which have been proposed and the anatomical restrictions of this "mesorectum" are sometimes contradictory. The aim of this study was to clarify the relationships of the "mesorectum" with the fascias and nerves of the pelvic cavity to harmonize the plane of dissection in its total extirpation. Four pelvises (2 male, 2 female) harvested from embalmed cadavers were studied by dissection and anatomico-imaging correlation. Two pelvises (1 male, 1 female) were injected with copolymer via the internal iliac and inferior mesenteric arteries. They were then frozen and sectioned sagittally into two hemi-pelvises for the dissection. The two other pelvises were initially studied in 5 mm cuts with CT scanning and magnetic resonance scanning in the sagittal and "transverse oblique" planes. They were then frozen and then cut sagittally into two hemi-pelvises. Each hemi-pelvis was then cut into anatomical sections with an electric saw similar to the radiological cuts: sagittal cuts on the right hemi-pelvis, and "transverse oblique" cuts on the left hemi-pelvis. It was noted that the "mesorectum" was carpeted behind and laterally by a postero-lateral fibrous envelope belonging to the pelvic visceral fascia and in front by a recto-genital membrane of variable nature corresponding to the "Denonvilliers fascia". The postero-lateral fibrous envelope splits into two leaves (anterior and posterior) in front of the sacral concavity and constitutes, lateral to the rectum, the armature of the pelvic plexus. These two leaves delineated the avascular retro-rectal space. The results of the correlations were deceptive. Their use was limited by dilatation of the rectum, which flattened the perirectal fat onto the pelvic walls on all the sections. Nonetheless, the description of the "mesorectum" and the demonstration of its enveloping fascias by dissection allowed the development of a dissection plane for its total extirpation.