Vascular anatomy of the transverse mesocolon and bidirectional laparoscopic D3 lymph node dissection for patients with advanced transverse colon cancer.

Laparoscopic D3 lymph node dissection for transverse colon cancer is technically demanding because of complicated anatomy. Here, we reviewed the vascular structure of the transverse mesocolon, explored the extent of the base of the transverse mesocolon, and evaluated the feasibility and oncological safety of D3 lymph node dissection. We retrospectively reviewed the clinical records of 42 patients with advanced transverse colon cancer who underwent curative surgery and D3 dissection at Kyushu University Hospital between January 2008 and December 2015. We examined the venous and arterial anatomy of the transverse mesocolon of each resection and compared surgical outcomes between patients who underwent laparoscopic D3 (Lap D3) and open D3 (Open D3) dissection. Patients included two with Stage I, 18 with Stage II, 20 with Stage III, and two with Stage IVA. Thirty-six (85.7%) and six (14.3%) patients underwent Lap D3 or Open D3, respectively. The tumor sizes of the Open D3 and Lap D3 groups were 7.8 and 3.7 cm, respectively (P < 0.001). The Lap D3 group had significantly less blood loss (26 mL vs 272 mL, P = 0.002). The other outcomes of the two groups were not significantly different, including 3-year overall survival (87.7% vs 83.3%, P = 0.385). We observed four patterns of the middle colic artery (MCA) arising from the superior mesenteric artery (SMA), and the frequency of occurrence of a single MCA was 64.3%. The right-middle colic vein (MCV) was present in 92.9% of resections and served as a tributary of the gastrocolic trunk, and 90.5% of the left MCVs drained into the superior mesenteric vein (SMV). The root of the transverse mesocolon was broadly attached to the head of the pancreas and to the surfaces of the SMV and SMA. Laparoscopic D3 lymph node dissection may be tolerated by patients with advanced transverse colon cancer.