Where does the first lateral pelvic lymph node receive drainage from?

BACKGROUND Lateral pelvic lymph node dissection (LPLD) in the treatment of rectal cancer has risks and benefits. Avoidance of unnecessary LPLD is important, however, preoperative and/or intraoperative accurate detection of lateral lymph node metastases have not been established. If the lateral lymph node to which the fluid first spread from the primary lower rectal cancer is detected accurately, it may guide the need for LPLD and may assist in avoiding unnecessary dissection. METHODS A total of 14 patients with T3 lower rectal cancer were evaluated to locate the lymph nodes through which indocyanine green (ICG) reached the lymphatics. After ICG was injected into the lower rectum via an endoscope preoperatively, total mesorectal excision was first performed, and LPLD was performed with infrared ray electronic endoscopy (IREE) to assess the degree of retention of ICG in each regional lymph node. RESULTS Drainage of ICG to lateral pelvic lymph nodes was observed in 6 of 14 patients (43%). All ICG-containing lymph nodes were detected by IREE. When present, lateral pelvic wall lymph node drainage was limited exclusively to the peri-internal iliac artery nodes. No obturator nodes were involved. CONCLUSION The first lateral lymph node that receives lymphatic drainage from lower rectal cancer is located around the internal iliac arteries.