Reversed anatomy in transanal lateral lymph node dissection: landmarks and pitfalls

Lateral lymph node dissection (LLND) is getting global attention as an a surgical option to reduce local recurrence in locally advanced rectal cancer. As the transanal total mesorectal excision (TaTME) is gaining popularity worldwide, a novel LLND approach was established adopting a two-team approach that combines the transabdominal and transanal approaches using the TaTME technique. This narrative review describes the advantages, anatomical landmarks, surgical techniques, and pitfalls of transanal LLND (TaLLND). The advantages of TaLLND include a magnified view and enhanced maneuverability of the laparoscopic instruments in the deep pelvis. TaLLND is also beneficial for LLND in patients with a history of pelvic surgery because surgeons can have access to the areas unaffected by previous surgery. To master the TaLLND technique, the procedure should be understood according to the following steps: S4 nerve identification, lateral space entry, lateral dissection, obturator vein, artery, and nerve identification, dissection along the external iliac vein, medial dissection, median and bottom dissection, dissection along the internal iliac artery, and dissection along the obturator nerve. TaLLND can be applied to highly advanced disease that requires combined resection of the major internal iliac vessels, pelvic nerves, or adjacent organs. In such cases, simultaneous transanal and transabdomiinal LLND utilizing a two team approach has advantages as these approaches can provide mutual complementary roles. TaLLND is expected to overcome the difficulty of transabdominal LLND and improve the quality of LLND.