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BACKGROUND: Controversies regarding the anatomical structure of Denonvilliers' fascia and its relationship with surrounding fasciae have sparked a heated discussion, especially concerning whether Denonvilliers' fascia is multilayered. This study aimed to expound on the anatomical structure of Denonvilliers' fascia and its correlation with the peritoneum from the sagittal view and clarify the complex fascial relationship. METHODS: Our study was performed on 20 adult male pelvic specimens fixed in formalin, including 2 entire pelvic specimens and 18 semipelvic specimens. The local adjacent organs and fasciae were dissected, and Denonvilliers' fascia was observed and removed for histological examination. RESULTS: Denonvilliers' fascia was typically single-layered and tough. On the sagittal plane, the peritoneum constituting the peritoneal reflection and Denonvilliers' fascia formed a "Y" shape. Denonvilliers' fascia originated from the peritoneal reflection, extended along the ventral side of the seminal vesicles and prostate, continuing caudally; its bilateral sides closely connected to the urogenital fascia (UGF) of the pelvic wall. In addition, histology preliminarily indicated that the basal cell layers of the peritoneum and Denonvilliers' fascia were continuous and formed a "Y" shape. Furthermore, the basal cells of the two peritonea extended to Denonvilliers' fascia, creating a fused double-layered structure. Some tiny blood vessels or a network of such vessels extended from the peritoneum to Denonvilliers' fascia. CONCLUSION: Denonvilliers' fascia, the extension of the peritoneum in the pelvic floor, appears as a single-layered "Y"-shape on the sagittal plane. Our study provides new support for the peritoneal fusion theory. Understanding the anatomical characteristics of Denonvilliers' fascia and its relationship with the UGF is of guiding significance for inexperienced colorectal surgeons to conduct rectal cancer surgery.

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BACKGROUND: Total mesorectal excision (TME) is conventionally performed according to Heald's principles through the so-called 'holy plane', between the visceral and parietal fasciae. However, urinary and sexual dysfunctions remain frequent postoperative complications. We proposed to preserve urogenital fascia (UGF) in TME, and this study aimed to clarify the anatomical basis of this technique and evaluate its efficacy and safety. MATERIALS AND METHODS: Cadaveric dissection was performed on 26 pelvises, and laparoscopic TME with UGF preservation was performed in 212 patients with mid-low rectal cancer. The fasciae and spaces related to TME were observed and described, and the clinical effect of UGF-preserving TME was analyzed. RESULTS: In the 26 cadavers, fascia propria of the rectum (FPR) presents as a fibrous capsule enveloping the mesorectum. UGF extends postero-laterally to the rectum, enveloping the hypogastric nerves and ureters. We demonstrated that the visceral fascia is actually the UGF, and FPR and visceral fascia (i.e. UGF) are two independent layers of fascia. Thus, FPR, UGF and parietal fascia form two avascular spaces behind the rectum. The plane ventral to the UGF is the real 'holy plane' for TME, rather than that dorsal to the UGF as is traditionally thought. Laparoscopic TME with UGF preservation was successfully performed in all 212 patients, with low perioperative complications (10.8%) and a low 3-year local recurrence rate (4.2%). Furthermore, the incidences of urinary and sexual dysfunctions at postoperative 6 months were only 6.1% and 10.8%, respectively. CONCLUSION: The avascular plane between the FPR and UGF (i.e. visceral fascia) is the real 'holy plane'. Laparoscopic TME with UGF preservation is a feasible radical surgery for mid-low rectal cancer, with better protection of urinary and sexual functions.

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Objective: To perform an anatomical observation on the extension of the mesocolon to the mesorectum and the continuity of the fasciae lining the abdomen and pelvis, in order to clarify the appropriate surgical plane of total mesorectal excision. Methods: This is an descriptive study. The operation videos of 61 cases (28 males, 33 females, median age of 61) were collected. All the patients underwent laparoscopic colorectal surgery from January 2018 to December 2018 in Yangpu Hospital, including low anterior resection for rectal cancer in 25 cases, left hemicolectomy for descending colon cancer in 15 cases, and subtotal resection of the colon for intractable constipation in 21 cases. Among these 21 constipation patients, 8 received additional modified Duhamel surgeries. Gross anatomy was performed on 24 adult cadavers provided by Department of Anatomy, Shanghai Jiaotong University School of Medicine, including 23 formalin-fixed and 1 fresh cadaver (12 males, 12 females). Sixty-one patients and 24 cadavers had no previous abdominal or pelvic surgical history. The anatomy and extension of fasciae related to descending colon, sigmoid colon and rectum, especially the morphology of Toldt fascia, and the continuities of mesocolon and mesorectum were observed carefully. The distribution characteristics of the fasciae and anatomical landmarks during laparoscopic surgery were recorded and described. Results: The anatomical study on 24 cadavers showed that visceral fascia was the densest connective tissue in the pelvic, posterolateral to the rectum, and stretched as a hammock to lift all pelvic organs. Among 61 patients undergoing laparoscopic surgery, 36 (59.0%) needed to free the left colon during operation, and Toldt fascia in the descending colon segment presented as potential, avascular and extensible loose connective tissue plane between the mesocolon and posterior Gerota fascia; 33 (54.1%) needed to free the rectum during operation, and Toldt fascia extended downward to pelvis as loose connective tissue between the fascia propria of the rectum and visceral fascia; the fascia propria of the rectum exposed completely in 32 (32/33, 97.0%) cases, which ran downward and fused with visceral fascia at the level of the fourth sacral vertebra. The anatomy of 24 cadavers also showed that fascia propria of the rectum fused with visceral fascia at the level of Waldeyer fascia. The fusion line of these two fasciae was supposed to be the extension of Waldeyer fascia. There were two avascular planes behind the rectum: one between the fascia propria of the rectum and visceral fascia, and the other between the visceral fascia and parietal fascia. In 8 constipation cases undergoing laparoscopic subtotal colon resection plus modified Duhamel operation, both mesocolon and mesorectum needed to be mobilized. It was obvious that the mesocolon of descending colon extended and became the mesocolon of sigmoid colon, and ran further into the pelvic and became the mesorectum. The colon fascia of descending colon served as the natural boundary of mesocolon extended downward as the fascia of sigmoid colon and the fascia propria of the rectum, respectively. Toldt fascia locating between mesocolon of descending colon and Gerota fascia extended to pelvis as the 'presacral space' between the fascia propria of the rectum and visceral fascia. Gerota fascia in descending colon segment extended as urogenital fascia in sigmoid colon segment and visceral fascia in the pelvis, respectively. In the cadaver anatomy study, the visceral fascia served as a corridor carrying the hypogastric nerve, and ureter was observed in 23 (23/24, 95.8%) cases. The visceral fascia passed from posterior to anterior lateral of rectum, fusing with Denonvilliers fascia in a fan shape. The pelvic plexus located exactly external to the junction of visceral fascia and Denonvilliers fascia. Pelvic splanchnic nerves went through the parietal fascia toward to the inferolateral of the pelvic plexus. Conclusion: Fascia propria of the rectum and the visceral pelvic fascia are two independent layers of fascia, and the TME surgical plane is between the fascia propria of the rectum and visceral pelvic fascia instead of between the visceral and the parietal pelvic fascia.

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Objective@#To perform an anatomical observation on the extension of the mesocolon to the mesorectum and the continuity of the fasciae lining the abdomen and pelvis, in order to clarify the appropriate surgical plane of total mesorectal excision.@*Methods@#This is an descriptive study. The operation videos of 61 cases (28 males, 33 females, median age of 61) were collected. All the patients underwent laparoscopic colorectal surgery from January 2018 to December 2018 in Yangpu Hospital, including low anterior resection for rectal cancer in 25 cases, left hemicolectomy for descending colon cancer in 15 cases, and subtotal resection of the colon for intractable constipation in 21 cases. Among these 21 constipation patients, 8 received additional modified Duhamel surgeries. Gross anatomy was performed on 24 adult cadavers provided by Department of Anatomy, Shanghai Jiaotong University School of Medicine, including 23 formalin-fixed and 1 fresh cadaver (12 males, 12 females). Sixty-one patients and 24 cadavers had no previous abdominal or pelvic surgical history. The anatomy and extension of fasciae related to descending colon, sigmoid colon and rectum, especially the morphology of Toldt fascia, and the continuities of mesocolon and mesorectum were observed carefully. The distribution characteristics of the fasciae and anatomical landmarks during laparoscopic surgery were recorded and described.@*Results@#The anatomical study on 24 cadavers showed that visceral fascia was the densest connective tissue in the pelvic, posterolateral to the rectum, and stretched as a hammock to lift all pelvic organs. Among 61 patients undergoing laparoscopic surgery, 36 (59.0%) needed to free the left colon during operation, and Toldt fascia in the descending colon segment presented as potential, avascular and extensible loose connective tissue plane between the mesocolon and posterior Gerota fascia; 33 (54.1%) needed to free the rectum during operation, and Toldt fascia extended downward to pelvis as loose connective tissue between the fascia propria of the rectum and visceral fascia; the fascia propria of the rectum exposed completely in 32 (32/33, 97.0%) cases, which ran downward and fused with visceral fascia at the level of the fourth sacral vertebra. The anatomy of 24 cadavers also showed that fascia propria of the rectum fused with visceral fascia at the level of Waldeyer fascia. The fusion line of these two fasciae was supposed to be the extension of Waldeyer fascia. There were two avascular planes behind the rectum: one between the fascia propria of the rectum and visceral fascia, and the other between the visceral fascia and parietal fascia. In 8 constipation cases undergoing laparoscopic subtotal colon resection plus modified Duhamel operation, both mesocolon and mesorectum needed to be mobilized. It was obvious that the mesocolon of descending colon extended and became the mesocolon of sigmoid colon, and ran further into the pelvic and became the mesorectum. The colon fascia of descending colon served as the natural boundary of mesocolon extended downward as the fascia of sigmoid colon and the fascia propria of the rectum, respectively. Toldt fascia locating between mesocolon of descending colon and Gerota fascia extended to pelvis as the 'presacral space’ between the fascia propria of the rectum and visceral fascia. Gerota fascia in descending colon segment extended as urogenital fascia in sigmoid colon segment and visceral fascia in the pelvis, respectively. In the cadaver anatomy study, the visceral fascia served as a corridor carrying the hypogastric nerve, and ureter was observed in 23 (23/24, 95.8%) cases. The visceral fascia passed from posterior to anterior lateral of rectum, fusing with Denonvilliers fascia in a fan shape. The pelvic plexus located exactly external to the junction of visceral fascia and Denonvilliers fascia. Pelvic splanchnic nerves went through the parietal fascia toward to the inferolateral of the pelvic plexus.@*Conclusion@#Fascia propria of the rectum and the visceral pelvic fascia are two independent layers of fascia, and the TME surgical plane is between the fascia propria of the rectum and visceral pelvic fascia instead of between the visceral and the parietal pelvic fascia.