The endorectal incision level of transanal total mesorectal excision (taTME): An emphasis on the distance from the anterior vs. posterior mesorectal ends to the anal verge.

BACKGROUND: There is no intraluminal guidance to ensure complete inclusion of the mesorectum in transanal total mesorectal excision (taTME). This study aimed to assess the distance difference between the anterior and posterior mesorectal terminal ends and the anal verge as a potential risk for residual mesorectum after resection. METHODS: Forty-four surgical specimens of extra-levator abdominoperineal excision (ELAPE) and 28 mid-sagittal cadaveric specimens were included to this study. The distance between the mesorectum terminal end (T) and the endoluminal landmarks (dentate line (D)/anal verge (A)) was measured and compared between men and women. Furthermore, 66 MRI images from The Cancer Imaging Archive (TCIA) were used to validate the same concept in a non-Asian population. RESULTS: The mesorectal terminal end was found to be aligned along with the levator hiatus. From the midsagittal view, the ELAPE specimens showed that the distance between T and A anteriorly was significantly longer than the same distance posteriorly (34.74±7.79mm vs 23.74±4.24mm, P<0.001). Similarly, the distance measured in the cadaveric specimens was significantly longer anteriorly than posteriorly (P<0.001). The validation cohort of non-Asian MRI image has confirmed the same (56.68±14.17mm vs. 38.18 ±10.42mm, P<0.001(. There was no significant difference between men and women. CONCLUSIONS: Because of the remarkable distance difference between the anterior and posterior mesorectal terminal ends away from the anal verge, the taTME proctectomy level may not meet the required mesorectal end. Thus, if TME is planned, aligning the proctectomy level around the levator hiatus would be the best place that can ensure complete TME.

[Anatomical observation and clinical significance of rectosacral fascia in total mesorectal resection].

Objective: To observe the anatomical architecture of rectosacral fascia and discuss the best plan for accurate peri-rectal dissection in laparoscopic/robotic total mesorectal resection (TME). Methods: A descriptive cohort study was carried out. A total of 127 patients with rectal cancer who underwent TME in the Department of Colorectal Surgery at the affiliated Union hospital of Fujian Medical University were included, patients' demographics with their pathological details and operation videos were collected for analysis. Another 20 high-definition images of post-TME surgical specimens were collected from our digital database. A total of 28 cadaveric models were examined at the Laboratory of Clinical Applied Anatomy, Fujian Medical University, to observe the anatomical details of rectosacral fascia. Results: (1) Anatomical observation showed that the pre-hypogastric fascia attaches to the proper fascia of the mesorectum in a horizontal arc posteriorly, forming the rectosacral fascia. If this fusion couldn't be identified and appropriately transected during posterior space dissection, it would be easy to destroy the proper fascia and dissect through the mesorectum resulting in residual mesorectum tissue. After the fascia transaction, the proper fascia of the mesorectum is still intact distally. The upper part of rectosacral fascia bilaterally re-separated again into the proper fascia and pre-hypogastric fascia. The pre-hypogastric fascia acts as a "fascia barrier" when dissecting the lateral space constantly from posterior to anterior. The right attachment of the rectosacral fascia was gradually transected. The pelvic plexus from the right S2-S4 was covered by the pre-hypogastric fascia which is considered the outer side layer of rectosacral fascia laterally. It was observed that the fascia continued with the anterior layer of the Denonvilliers' fascia, which has been transected during anterior space dissection. The proper fascia, which is the inner side layer of rectosacral fascia laterally, was still intact. The edge of the right rectosacral fascia attachment ran obliquely from the back and upward into the front direction. The left extension was similar to the right. (2) Cadaveric specimens: at the level of the lower edge of S4 vertebral body, the pre-hypogastric fascia fused with the proper fascia to form the rectosacral fascia. The right attachment margin of the rectosacral fascia was cut off step by step. The attachment margin of the rectosacral fascia went from the back and upward to the front downward direction. The right edge of rectosacral fascia attachment continued with the anterior layer of the Denonvilliers' fascia at the pre-rectal space and attached to the pre-hypogastric fascia laterally. The pelvic plexus sends out many tiny rectal branches on the anterolateral side, which pass through the transitional area between pre-hypogastric fascia and the anterior layer of the Denonvilliers' fascia to innervate the rectum. (3) TME specimens observation: the posterior attachment of rectosacral fascia was curved around the mesorectum with bilateral oblique attachments. The mesorectum was covered by fusion fascia below the posterior and bilateral attachment margin while it was covered only by the proper fascia above it. Conclusion: according to the morphological characteristics of rectosacral fascia, the rectosacral fascia should be dissected at the level of S4 vertebral body posterior to the rectum in an arc, shape and then enter the superior-levator space. Before dissecting the bilateral spaces, the anterior space of the rectum should be dissected first. The anterior layer of the Denonvilliers' fascia should be cut off into an inverted "U" shape, and then the lateral space should be dissected from anterior to posterior. Finally, the lateral attachment of rectosacral fascia was transected to ensure the integrity of the mesorectum without damaging the pelvic plexus branches and NVB.

The 'multilayer' theory of Denonvilliers' fascia: anatomical dissection of cadavers with the aim to improve neurovascular bundle preservation during rectal mobilization.

AIM: Denonvilliers' fascia is thought to be a multilayered fascial structure, based on its embryological development with the neurovascular bundle embedded within it. Recently, this theory had been proven histologically and by confocal microscopy in many published articles. However, the literature does not report on how surgeons can identify these structures. We aimed to determine the optimal surgical approach for preserving these critical structures. METHOD: Eighteen cadavers (13 male/five female) were included and treated according to the ethical considerations stated in the donation consent of our institution. Dissection was performed with the assistance of binocular loupes for better anatomical detail. The compositions of the prerectal fascia and the neurovascular bundle were observed and recorded at different levels of dissection using a high-definition camera. RESULTS: The theoretical multilayered fascia was found in male specimens as three fascial layers originating from the perineal body, seminal vesicles and posterior bladder neck. The first layer merged posterolaterally and fused with the rectosacral fascia (Waldeyer's fascia). The neurovascular bundle in male specimens was observed piercing the second and third layers, while the first layer acted as a protective cover. Dissection of female specimens demonstrated only one layer in the prerectal space. CONCLUSION: Intiating anterior rectal mobilization by incising the peritoneum posterior to its reflection seems to be anatomically correct to preserve DVF. However, its applicability may be difficult in a narrow chanllenging pelvis. The lateral rectal ligaments and Waldeyer's fascia should be dissected from their attachments to the proper fascia of the rectum.