Evaluation of lymph flow patterns in splenic flexural colon cancers using laparoscopic real-time indocyanine green fluorescence imaging.

Purpose: The treatment of splenic flexural colon cancer is not standardized because the lymphatic drainage is variable. The aim of this study is to evaluate the lymph flow at the splenic flexure.

Methods: From July 2013 to January 2016, consecutive patients of the splenic flexural colon cancer with a preoperative diagnosis of N0 who underwent laparoscopic surgery were enrolled. Primary outcome is frequency of the direction of lymph flow from splenic flexure. We injected indocyanine green (2.5 mg) into the submucosal layer around the tumor and observed lymph flow using the laparoscopic near-infrared camera system in 30 min after injection.

Results: Thirty-one patients were enrolled in this study. The lymph flow was visualized in 31 patients (100 %) without any complications. No case exhibited lymph flow in both the left colic artery (LCA) and left branch of the middle colic artery (lt-MCA) areas. There were 19 cases (61.3 %) with lymph flow directed to the area of the root of the inferior mesenteric vein (IMV), regardless of the presence of the left accessory aberrant colic artery. Lymph node metastases were observed in six cases (19.4 %), and all of the involved lymph nodes existed in lymph flow areas determined by real-time indocyanine green fluorescence imaging.

Conclusions: The findings of the lymph flow pattern of splenic flexure suggest that lymph node dissection at the root of the IMV area is important, and it may be not necessary to ligate both the lt-MCA and LCA, at least in cases without widespread lymph node metastases.