Lymph Node Distribution in the D3 Area of the Right Mesocolon: Implications for an Anatomically Correct Cancer Resection. A Postmortem Study

BACKGROUND: Data on lymph node distribution in the right colon D3 area are scarce, especially for nodes posterior to the superior mesenteric vessels. OBJECTIVE: The aim of this study was to determine whether nodes exist posterior to the superior mesenteric vessels and if arterial crossing patterns affect node distribution. DESIGN: This is an anatomical postmortem study. SETTINGS: This study was conducted at the following institutions: Department of Gastrointestinal surgery/ Pathology, Vestfold Hospital Trust, Norway; Institute for Pathology, University of Belgrade, Serbia; and Anatomy Sector, University of Geneva, Switzerland. PATIENTS: Fresh human cadavers were selected to undergo autopsy. INTERVENTION: A predefined D3 area was removed from cadavers, fixed in formaldehyde, divided into 3 vertical compartments with regard to the superior mesenteric vessels. Vertical compartments were further divided into 8 compartments. Millimeter slices were analyzed at histology. MAIN OUTCOME MEASURES: Lymph nodes >= 1 mm were counted in each compartment. RESULTS: Twenty-six cadavers (14 men), median age 76 years, were included. Mean node number per cadaver was 15.9 +/- 7.4. Lateral, anterior, and posterior vertical compartments contained median 5.5 (1-11), 5 (2-21), and 5 (0-11) nodes. The effect of the ileocolic artery crossing pattern on node number in the posterior vertical compartment was p = 0.020. Anterior/posterior ileocolic artery compartments contained nodes in 58% and 85% cadavers with median of 1(0-7) and 2(0-5). These compartments showed a significant difference in node numbers depending on the ileocolic artery crossing pattern, p < 0.001 (posterior crossing) and p < 0.001 (anterior crossing). The middle colic artery compartment contained nodes in all cadavers with a median of 2 (1-4). The association between volume and total number of nodes in the D3 area was statistically significant, p < 0.001. LIMITATIONS: Nodes posterior to the superior mesenteric vessels do not necessarily have clinical relevance. CONCLUSION: Anatomically correct D3 resection implies posterior vertical compartment removal with posterior ileocolic artery crossing. Addition of the lateral vertical compartment to routine right colectomy has an improvement potential of 5 to 6 nodes.