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Background: Two points are controversial in the anatomy of the mesorectum: (1) its origin; and (2) the existence of the lateral ligaments. We studied these structures in animals and in human fetuses., Methods: Dissections were performed on quadrupedal mammals (29 dogs and 32 pigs) and 28 primates (Macaca apes). Moreover, macroslices of Macaca ape and of 182 human fetuses were examined histologically., Results: In quadrupedal mammals, we found no traces of any adipose masses comparable to the human mesorectum nor were there ligaments of suspension. In the ape, the adipose tissue in the mesosigmoid forms an adipose cuff that completely surrounds the extraperitoneal rectum. Two dense connective bands were found between the lateral wall of the pelvis and the perirectal tissue. Both the mesorectum and the lateral ligaments were clearly identified in the sections of human fetus only at the end of the fifth month but not earlier., Conclusions: On the basis of our analysis of 3 animal species, we conclude that the mesorectum and lateral ligaments are absent in quadrupedal mammals but are present in primates. Therefore, we hypothesize that these structures appeared with the attainment of the upright position, even though other hypotheses are possible.

Purpose: For many years, poor vascularization of the short rectal stump has been considered the main cause of leakage. The purpose of this study was to evaluate the vascularization of the rectal stump after total mesorectal excision., Methods: We studied the iliac vascularization on 28 volunteers with healthy rectum to have an anatomic basis. Then, we studied the vascularization of the rectal stumps after total mesorectal excision by using angio computed tomography at seven and three months after operating on 22 patients; we validated this technique by studying the vascularization using angio computed tomography in 18 rectal specimens from cadavers., Results: Both in healthy rectums and in rectal stumps after total mesorectal excision, there is good vascularization sustained by middle and inferior rectal arteries. The former is more important and frequent as described in previous literature., Conclusions: The vascularization of the short rectal stump is generally well represented even after total mesorectal excision.

Purpose: Many authors have discussed the presence and the importance of the lateral ligaments of the rectum. Our contribution aims at clarifying some aspects of surgical anatomy that help in the preservation of the urogenital functions and may influence the surgical practice., Methods: From 1994 to 1998 we examined 27 fresh cadavers and five embalmed pelves. We performed all dissections with a technique similar to that used for the surgical mobilization of the rectum., Results: The lateral ligaments of the rectum are trapezoid structures originating from mesorectum and are anchored to the endopelvic fascia; as lateral extensions of the mesorectum, they must be included in the surgical specimen. According to our results, three main structures can be recognized laterally to the rectum: 1) the lateral ligament, which does not contain important structures; 2) the inferior hypogastric plexus and the urogenital bundle; and 3) the lateral neurovascular pedicle of the rectum that comprises the nervi recti and the middle rectal artery, both running under the lateral ligament, although at different angles., Conclusion: At the point of insertion into the endopelvic fascia, the lateral ligaments run close to the urogenital bundle. Nevertheless, the dissection at its attachment is safe if the urogenital bundle is kept under visual control.

The modern approach to rectal surgery aims at preserving the nerves to the urogenital system. The relationships between the lateral aspects of the rectum and the surrounding structures represent one of the most controversial points in the surgical anatomy of this area. This study was conducted on 27 fresh cadavers and 5 frozen pelvises. All dissections were performed with a technique similar to that used for the surgical mobilisation of the rectum. The lateral ligaments can be considered extensions of the mesorectum; they originate laterally to the middle portion of the rectum and descend posterolaterally to anchor to the endopelvic fascia. The lateral neurovascular pedicle of the rectum, comprising the middle rectal artery and the transverse autonomic nervous fibres, courses partially beneath the lateral ligament. The urogenital nervous bundle runs close to the point of insertion of the lateral ligaments in the endopelvic fascia, but is not covered with the same layer that forms the ligament itself. Anatomical dissection of cadavers is of invaluable help to the surgeon as it represents the basis for easy recognition of all the various structures in the rectal area.

Background/aims: The investigators studied the surgical anatomy of the main structures involved in the mobilization of the rectum (Denonvilliers' fascia, mesorectum, middle rectal artery, superior and inferior hypogastric plexuses)., Methodology: The study was carried out on 20 cadavers (17 unembalmed and 3 embalmed). To study Denonvilliers' fascia, ten embryos and fetuses (11 mm to 80 mm CRL) were also examined., Results: Denonvilliers' fascia originates from the fusion of the primary pouch of Douglas. The two leaves making up this structure are easily separated. The mesorectum surrounds the rectum on three sides; it is easily separated from the presacral fascia and its connective tissue is bordered by a thin membrane. The middle rectal artery varies in appearance rate, origin, size, distribution and anastomosis. It runs under the lateral ligament and also sends branches to the genital apparatus. Of the two hypogastric plexuses, the inferior is the most difficult one to identify. Its superior branches extend to the rectum, and the inferior ones to the genital apparatus. Because the anterior part contains the parasympathetic nerves and the middle rectal artery, this region is at major risk during surgical dissection., Conclusions: A sound understanding of the surgical anatomy of the rectum enables the surgeon to perform a more correct and reasonable procedure in terms of both the extent of surgical treatment and the preservation of important anatomical structures.