Layer by Layer: The Anatomical 'Onion Peel' Approach to Surgery Beyond Total Mesorectal Excision

The global incidence of rectal cancer is rising, accompanied by the increasing use of neoadjuvant chemoradiotherapy. Although this approach improves oncological outcomes, it frequently increases operative difficulty during rectal resection. Achieving a negative circumferential resection margin (CRM) remains critical to reducing local recurrence. While clear margins are often attainable utilising the standard total mesorectal excision (TME) plane, dissection beyond TME is increasingly required following neoadjuvant radiation or for locally advanced or recurrent disease. Such surgery demands detailed knowledge of complex pelvic anatomy and sound operative strategies to achieve optimal outcomes.

This publication presents a novel 'onion peel' approach to pelvic anatomy comprising five sequential layers. Layer 1-the TME plane; Layer 2-the ureterohypogastric fascia and anterior viscera; Layer 3-lymphovascular structures; Layer 4-neural structures and Layer 5-musculoskeletal anatomy. Within each layer, key anatomical features are outlined alongside practical operative strategies to facilitate safe dissection and recognition of vital structures.

This paper provides colorectal surgeons with a novel overview of the anatomy surrounding the mesorectal envelope along with simple operative strategies to enter and safely dissect planes beyond TME.