Purpose: Although the existence of lateral lymphatic drainage of the rectum has been verified anatomically, the clinical importance of it has not yet been fully investigated. The lack of a definition of lateral lymphatic flow makes it difficult to analyze and compare data. The aim of this study was to define the concept of lateral lymphatic drainage and explore its relationship to total mesorectal excision and to disclose the incidence and efficacy of dissection of lateral node involvement.
Methods: Review of anatomic and clinical research on lateral lymphatic flow was made to create a definition of lateral lymphatic flow. Based on this review, a three-space dissection was designed and applied. A retrospective analysis was made of 764 patients with rectal cancer treated by a curative three-space dissection operation during 20 years starting in 1975 at Cancer Institute Hospital.
Results: Lateral lymphatic flow passes from the lower rectum and through the lateral ligament laterally beyond the mesorectum. It then ascends along the internal iliac artery and, in addition, inside the obturator space. Sixty-six cases proved to have lateral node involvement, which comprised 8.6 percent of all rectal cancer and 16.4 percent of low-lying (lower margin below 5 cm above the dentate line) rectal cancer cases. The five-year survival rate of these 66 cases was 42.4 percent. There were 16 cases that had a solo lateral node involvement.
Conclusion: Lateral lymphatic flow from low-lying rectal cancer passes outside the boundaries of total mesorectal excision but within the range of curative surgery by three-space dissection.