Revising Fascial Anatomy With a Focus on the Fusion Fascia in Mesenteric Gastrointestinal Cancer Surgery.

Recent advances in laparoscopic and robotic surgery have necessitated a critical re-evaluation of fascial anatomy relevant to mesenteric excision in gastrointestinal (GI) cancer surgery. Traditional models based on peritoneal fusion have often conflated mesothelial structures with fascia, resulting in conceptual imprecision regarding the fusion fascia (FF) and associated dissection planes. In this review, we integrate current surgical observations, histological evidence, and developmental anatomy to reformulate the anatomical conceptualization of connective tissue interfaces integral to mesenteric-based GI cancer surgery. Our synthesis indicates that Gerota's fascia, encompassing the anterior renal fascia, is an inherent anatomical structure rather than a surgical artifact thickened by dissection at the fusion plane. The subperitoneal fascia interweaves with Gerota's fascia but does not fold back into the mesentery at the base of the aorta. The FF is neither a dense connective tissue membrane nor a remnant of mesothelial fusion, but rather a loose connective tissue interface resulting from developmental remodeling of the digestive system. Dissection of the FF reveals a membranous covering on the deep surface of the mesentery, contributing to the formation of an intact resection package. Commonly used but poorly defined terms (e.g., "posterior pancreatic fascia") are reinterpreted within this framework as surgically revealed manifestations of mesenteric dissection. This updated conceptual scheme offers a unified, anatomically grounded approach to mesenteric surgery that is consistent with intraoperative reality. It also underscores the need for surgical anatomy to evolve in response to modern techniques and for further refinement based on operative evidence.