Anatomic study of lateral pelvic lymph nodes: Implications in the treatment of rectal cancer

PURPOSE: Lateral pelvic lymphadenectomy remains a controversial issue in rectal cancer surgery. Beyond clinical results, disagreement includes surgical anatomy aspects and definitions, as wells as lack of information about location, groups, and number of lymph nodes, all of which makes comparison of results difficult. We performed a systematic examination of the number and distribution of lateral pelvic lymph nodes using cadaveric dissection. METHODS: Sixteen formalin-fixed cadavers were dissected (14 males). Dissection fields were divided according to the three surgical groups of pelvic wall lymph nodes: presacral, obturator, and hypogastric. Number and site of excised lymph nodes was recorded, noting neurovascular relationships. RESULTS: A total of 458 lymph nodes were found, with a mean of 28.6 nodes per pelvis (range, 16-46). Lymph node size ranged from 2 to 13 mm. The highest number of lymph nodes was found in the obturator fossa group (mean, 7; range, 2-18). Hypogastric lymph nodes were found lying predominantly above the inferior hypogastric nerve plexus but reaching the deep pelvic veins. CONCLUSIONS: The mean number of lymph nodes found in lateral pelvic wall compartments was 28.6 per specimen. The group containing most lymph nodes lies in the obturator fossa. Complete excision of hypogastric lymph nodes demands a deep pelvic dissection of neurovascular structures.