Anatomical characterization and visualization of the left dominant inferior mesenteric ganglionated plexus for nerve sparing colorectal surgery.

The current Japanese colorectal surgical guideline excludes preservation of the inferior mesenteric plexus (IMP) from the category "preservation of all autonomic nerves (AN4)." However, clinical and experimental evidence indicates that the IMP surrounding the inferior mesenteric artery (IMA) is essential for maintaining postoperative bowel, urinary, and sexual function. In clinical practice, the inferior mesenteric ganglia (IMGs) within the IMP are frequently overlooked because they are small, inconspicuous, and difficult to identify during colorectal surgery. To clarify their surgical relevance, we analyzed the anatomy of the IMP and IMGs using physical and virtual dissection of 17 formalin-fixed human cadavers. Left-dominant IMGs and one to four ganglion clusters were consistently identified on IMA's left side. Importantly, the location and size of the IMGs showed significant correlations with the branching patterns of the IMA. These findings support the concept of a "left-dominant inferior mesenteric ganglionated plexus," which is rarely visible in standard anterior or right-oblique laparoscopic views. From a surgical perspective, our results indicate that preoperative assessment of IMA branching patterns may allow prediction of the size and extent of the IMGs, thereby facilitating nerve-sparing colorectal surgery. When identification is challenging, intraoperative confirmation using lymphatic or nerve markers may further improve preservation of autonomic function.