Triangle of Marcille: the anatomical gateway to lateral pelvic exenteration.

Background: To perform more radical surgery for complex pelvic malignancies and recurrent colorectal cancer, the surgeon must increasingly operate outside the conventional anatomical planes. Published in 1963 the 'Triangle of Marcille' (lumbosacral triangle) remained primarily of intellectual interest being found lateral to the traditional operating field. However, with the advancement of complex colorectal and gynaecological surgery it now provides a schema to assist surgeons in becoming acquainted with a complex and poorly understood anatomical region. Additionally, it prepares the surgeon for the extent of lateral dissection required to achieve the 'holy grail' for oncological surgery in pelvic malignancy, the complete resection (R0). Methods: To prosect a preserved cadaver in order to demonstrate, in vivo, the contents and borders of the Triangle of Marcille for the purposes of teaching surgeons and future surgeons. Results: The Triangle of Marcille is both described and demonstrated in vivo, illustrated with diagrams and photographs. The importance of this region to the surgical management of complex colorectal and gynaecological surgery is discussed. Conclusion: The Triangle of Marcille is a vital anatomical region for advanced pelvic surgery, particularly in the current era of pelvic exenteration, and especially for those that include the lateral pelvic compartment.