Above the sphincters the rectum is demarcated into three 3cm segments by the valves of Houston. The rectum has a broad mesenteric attachment in the sacral hollow and is closely applied to the sacral plexus of veins and the sympathetic and parasympathetic pelvic nerve plexuses.
The lateral peritoneal reflections of right and left colon represent the margins of the colonic fusion fascias. When the right or left colon is elevated it creates a doubling of the adjacent posterior parietal peritoneum and that double thickness forms the “white line” of Toldt. Incision between that white line and the colon wall enters the bloodless fusion fascia plane. In the proper plane, the colon mesentery peels off easily with a moist sponge stick. Cutting through the parietal peritoneum enters the retroperitoneal space which is vascular.
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