Mesocolon

Mesocolon is a peritoneal fold that attaches portions of the large intestine to the posterior abdominal wall, forming the mesentery of the colon. It permits passage of vessels, nerves, and lymphatics and helps stabilize the colon during movement.

Anatomy: The colon is intraperitoneal in its transverse and sigmoid portions, each supported by a mesocolon (the transverse mesocolon and the sigmoid mesocolon). The ascending and descending colon are typically secondarily retroperitoneal and lack a significant mesocolon. The mesocolon contains the colic vessels, their accompanying veins, lymphatics, nerves, and fat.

Contents and attachments: The transverse mesocolon binds the transverse colon to the posterior abdominal wall; the sigmoid mesocolon binds the sigmoid colon to the pelvic wall. Vascular supply arises from the middle colic arteries to the transverse colon, and from the left and right colic arteries to the other portions; venous drainage parallels these vessels. Innervation is via the mesocolic autonomic plexuses corresponding to the midgut and hindgut portions.

Development: The mesocolon develops from the dorsal mesentery of the primitive gut. Rotations and fixation position the intestines, leaving the transverse and sigmoid portions attached by mesocolic folds.

Clinical relevance: Knowledge of mesocolic planes guides colorectal surgery, particularly colectomy. Variations in attachment may affect the risk of internal hernias and patterns of lymphatic spread by tumor.