The mesorectum is a fatty tissue structure surrounding the rectum, the final section of the large intestine. Though not formally recognized in traditional anatomy, it is acknowledged in surgical and radiological contexts, especially for rectal cancer staging. This structure begins where the rectum connects with the sigmoid colon and extends to the levator ani muscles. It forms a cushion around the rectum, particularly towards the back and sides, supporting its position within the pelvic cavity.
Anatomy and Structure
The mesorectum is composed of fatty tissue. Encasing this fatty tissue is a layer of connective tissue known as the mesorectal fascia. This fascial layer acts as an outer boundary, containing the various elements within the mesorectum.
Within this fatty envelope, a network of blood vessels, lymphatic vessels, and lymph nodes can be found. Blood vessels supply and drain blood from the rectum through the mesorectum. The lymphatic vessels and their associated lymph nodes are also embedded within this tissue. The mesorectal fascia and its contents help define boundaries for surgical dissection and can limit disease spread.
Clinical Relevance in Rectal Cancer
The mesorectum is important in the management of rectal cancer due to its role in disease spread. Rectal cancer cells often spread along the lymphatic pathways within the mesorectum. These lymph nodes are often the first site where cancer cells are found as the disease spreads.
Preserving the mesorectal fascia is important for preventing local cancer recurrence. This fascial barrier can help contain tumor cells and limit their spread into surrounding pelvic tissues. The extent of cancer invasion into the mesorectum, including lymph node involvement, directly influences treatment decisions and patient prognosis.
Total Mesorectal Excision
Total Mesorectal Excision (TME) is a widely recognized surgical approach for treating rectal cancer, particularly for tumors located in the middle and lower rectum. The main objective of TME is to completely remove the rectum along with its surrounding mesorectum, including all associated lymph nodes and blood vessels, as a single, intact specimen. This meticulous dissection is performed along a natural, relatively avascular plane, often referred to as the “holy plane,” which lies between the mesorectal fascia and the parietal pelvic fascia.
This precise surgical technique aims to ensure that no tumor cells are left behind in the surgical area, minimizing the risk of local cancer recurrence. TME can be performed using different approaches, including traditional open surgery, minimally invasive laparoscopic techniques, or robot-assisted surgery. For tumors located very low in the rectum, a transanal approach, known as transanal total mesorectal excision (TaTME), can be combined with an abdominal approach, offering improved visualization in the deep pelvis.
Benefits of Total Mesorectal Excision
A carefully executed Total Mesorectal Excision offers significant advantages for individuals with rectal cancer. The procedure has been shown to reduce the rates of local cancer recurrence, which refers to the return of cancer in the same area after treatment. Studies have indicated that TME can decrease local recurrence rates from a range of 20-45% with older surgical methods to approximately 3-9%.
This reduction in local recurrence directly contributes to enhanced long-term survival for rectal cancer patients, with some reports showing an increase in five-year survival rates by 20% or more. While challenging, surgeons also aim to preserve nerve function during TME to help maintain urinary and sexual function after surgery, which can improve a patient’s quality of life.