Lymph Node Distribution in the D3 Area of the Right Mesocolon

Abstract

Data on lymph node distribution in the right colon D3 area are scarce, especially for nodes posterior to the superior mesenteric vessels. 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. This is an anatomical postmortem study. 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. Fresh human cadavers were selected to undergo autopsy. 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. Lymph nodes ≥1 mm were counted in each compartment. 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. Nodes posterior to the superior mesenteric vessels do not necessarily have clinical relevance. 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.