Autonomic nerves cross the posterior plane of rectal dissection

This investigation was an anatomical study to determine whether branches of the pre-sacral autonomic plexus cross the posterior plane of surgical dissection to supply the rectum. Initially four cadaver hemi-pelves were dissected. Twelve patients undergoing full rectal mobilization were then studied at operation. In all subjects the pre-sacral nerves were arranged as a plexus below the sacral promontory, rather than as individual left and right nerve trunks. Structures thought to be nerves were identified crossing the plane of posterior mobilization of the rectum. They were traced towards their origin and destination, photographed and representative fibres biopsied. A total of 42 such structures were biopsied (16 in cadavers, 26 in operative cases) and 40 were confirmed to be nerves. These nerves connect the pre-sacral autonomic plexus with the posterior aspect of the rectum and were found at all sacral levels. In the operative cases the level of the positive biopsies were S1-six, S2-six, S3-five, S4-four, S5-three. The posterior plane of rectal dissection is therefore crossed by autonomic nerves that innervate the rectum. The pre-sacral nerves have been found to form a plexus in all subjects.