[Reappraisal of the lateral rectal structure]

Colorectal surgeons have focused on the lateral structure of rectum for a long time and lateral ligament is the common term to depict this structure. A better understanding of lateral rectal structure could be beneficial to performing the total mesorectum excision (TME) procedure and protecting patients' urinary, sexual and defecation function. The main controversies focus on two aspects: (1) Does the lateral ligament exist? (2) What dose it contain? Does the middle rectal artery exist? Up to now, anatomic studies have failed to reach consensus on the lateral rectal structure. However, surgeons do find the lateral rectal ligament during surgery and it may be the pathway for lateral lymph node metastasis in rectal cancer. The lateral rectal structure contains the middle rectal artery, nerve branches, lymphatics and adipose fibrous tissue around them. We summarize our clinical experience and conclude that the middle rectal artery appears in lateral ligament constantly but some of them are too small to be easily observed. Therefore, regarding the perspective of membrane anatomy, embryology and surgery, this structure may be more appropriate to be called the "lateral mesorectum". We propose this new term based on the previous literature and our own experience for the readers' reference.

Reappraisal of the lateral rectal ligament: an anatomical study of total mesorectal excision with autonomic nerve preservation

PURPOSE

The term "lateral rectal ligament" in surgery for rectal cancer has caused confusion regarding its true existence and contents. In previous studies, investigators claimed the existence of the ligament and described its topographical features as neurovascular structures and their surrounding connective tissues located at the anterolateral aspect of the distal rectum or the posterolateral aspect of the middle rectum. The purpose of this study is to evaluate the structure of the so-called "lateral rectal ligament" in cadaver dissections.

METHODS

Dissection was performed in nine cadavers (eight males and one female, aged 73 to 94 years) in accordance with typical total mesorectal excision techniques. During dissection, structures related to "the ligament" were examined and images recorded.

RESULTS

At the anterolateral aspect of the distal rectum, the middle rectal artery was noted to be crossing the fusion of Denonvilliers' fascia and the proper rectal fascia. At the posterolateral aspect of the middle rectum, there was a structure which consisted of the rectal nerves running through the fusion of the pelvic fasciae. Although called "ligaments," neither structure contained discrete strong connective tissue fixing the rectum to the pelvic wall.

CONCLUSIONS

The proper rectal fascia and surrounding pelvic fasciae fuse firmly anterolaterally and posterolaterally where neurovascular structures course toward the rectum. During a total mesorectal excision, the surgical dissection plane coincides with the fused part of the fasciae, which had long been considered the "lateral rectal ligament."