Defining minimal clearances for adequate lymphatic resection relevant to right colectomy for cancer: a post-mortem study.

BACKGROUND: There has been a lengthy discussion on the extent of lymphatic resection for right-sided colon cancer and the central borders of the mesentery that are not yet defined. The objectives of this study are to define minimal clearances for adequate lymphatic resection in regard to colic artery origins and the superior mesenteric artery (SMA) and vein (SMV) relevant to right colectomy. METHODS: Central mesenteric lymph vessels, nodes, and blood vessels were dissected in 16 cadavers. Cranial-caudal clearances were defined as distances between an individual colic artery origin (ileocolic, right colic, and median colic artery) and the outermost lymphatic vessel within its lymphovascular bundle, cranial and caudal along the SMA. Long lymphatic vessels crossing the SMV between arterial bundles were counted and they constituted the medial clearances. An arbitrary watershed between small bowel and colonic lymph was localized. Immunohistochemistry was performed to histologically verify lymphatic vessels. RESULTS: Cranial-caudal clearances were ileocolic 3.6 ± 1.9 and 5.7 ± 1.9; right colic 2.8 ± 1.6 and 3.3 ± 1.0; middle colic artery bundle 6.3 ± 2.7 and 5.9 ± 2.4 mm, respectively. Long lymphatic vessels crossing the SMV between arterial buntles and approaching the SMA were found in all cadavers (antero/posteriorly in 12, only anteriorly in 4), median 3.5 (1-7) long lymphatic vessels anteriorly, and 1.5 (0-5) posteriorly per cadaver. CONCLUSIONS: Right colonic lymphovascular bundles are volumes of mesenteric tissue that surround the superior mesenteric vessels anteriorly and posteriorly. Long lymphatic vessels traverse the superior mesenteric vein anteriorly/posteriorly approaching the superior mesenteric artery between arterial bundles and placing the medial clearance on the left side of the artery. These do not correlate to arterial crossing patterns. Cranial-caudal clearances determine the tissue to be removed superior/inferior to arterial origins together with long lymphatic vessels transversing independently between the lymphovascular bundles placing the weight of lymphatic resection on the mesenteric tissue and not on the level of vessel division (High tie).