Objective: To investigate the pattern of distribution of the circumferential fascia of the rectum and elucidate its clinical implications. Methods: In this descriptive study, we examined the gross anatomy of four male hemipelvic cadaveric specimens from the Department of Anatomy at Fujian Medical University and the histological features of 16 fresh postoperative specimens from patients who had undergone total mesorectal excision for rectal cancer at the Department of Colorectal Surgery, Union Hospital, Fujian Medical University, between January and December 2022. The resultant combination of gross anatomical and histological features was employed to assess the following areas: (1)the morphology of the anterior mesorectum and fascia at the peritoneal reflection; (2)the caudal attachment point of Denonvilliers' fascia; (3) the fusion area of the pelvic plexus and the pre-hypogastric fascia; (4)the lateral and posterior attachment edges of the rectosacral fascia; and (5) selected histological features. Results: Our findings were as follows. (1) At the peritoneal reflection, the anterior mesorectum forms a triangular fat pad with a dense fascial structure. The base of this pad extends anteriorly across the most caudal point of the peritoneal reflection, with Denonvilliers' fascia originating from the anterior side of the triangle, near the bladder side of the peritoneum craniad to the peritoneal reflection. (2) The caudal attachment of Denonvilliers' fascia is at the angle between the seminal vesicles, the ampulla of the vas deferens, and the prostate. It adheres tightly to the prostatic capsule and vascular bundles pass through its cephalic side. (3) The pre-hypogastric fascia transitions laterally to merge with Denonvilliers' fascia; its middle part being inseparable from the main body of the pelvic plexus, which gives rise to the nerves that innervate the rectum. (4) The rectosacral fascia is formed by fusion of the fascia propria with the pre-hypogastric fascia. The resultant fused fascia bifurcates into two leaves on the right side; the outer leaf being the pre-hypogastric fascia and the inner leaf the fascia propria. (5) Histologically, the peritoneal reflection zone shows cuboidal epithelium of the peritoneum at its lowest point with no detectable origin of Denonvilliers' fascia. The anterior side of the peritoneal reflection, from which Denonvilliers' fascia originates, has a dense double-layered fascial structure comprising thick collagen fiber (16/16). The fascia propria exhibits a thinner and looser collagen fiber structure and its origin varies between individuals, 13/16 originating together with Denonvilliers' fascia from the craniad side of the peritoneal reflection, and 3/16 originating separately from the most caudal point of the peritoneal reflection. The caudal edge of Denonvilliers' fascia has a double-layered fascial structure with multiple S100-stained areas. The posterior edge of the rectosacral fascia has a fused fascial structure, thick nerve fibers being clearly observable between collagen fibers originating from the pre-hypogastric fascia under high magnification. The lateral edge of the rectosacral fascia extends interiorly, maintains the integrity of the fascia propria. Conclusions: In this study, we investigated the pattern of distribution of the circumferential fascia of the rectum by cadaveric dissection and histological examination of postoperative specimens. We found that the anterior mesorectum forms a triangular fat pad that can serve as a reference for dissection anterior to Denonvilliers' fascia, by making incisions 1 cm above the peritoneal reflection. The region of fusion of Denonvilliers' fascia with the prostatic capsule on the caudal side is rich in neurovascular bundles, contradicting the traditional view of a retroprostatic plane. This finding supports the practice of cutting Denonvilliers' fascia 0.5 cm above the base of the seminal vesicles. The fusion of the fascia propria with the pre-hypogastric fascia posteriorly forms the rectosacral fascia, which bifurcates into two leaves on both sides of the rectum, the inner leaf being the fascia propria and the outer leaf the pre-hypogastric fascia. These transition anteriorly to become Denonvilliers' fascia and fuse densely with the main body of the pelvic plexus on both sides. These findings provide a theoretical foundation for protecting the pelvic plexus and hypogastric nerve by transecting Denonvilliers' fascia and then dissecting in a top-to-bottom direction (i.e., from anterior to caudal), ultimately leading to the transection of the pre-hypogastric fascia.
目的： 对直肠环周筋膜的分布模式进行研究。 方法： 采用描述性研究的方法。选择福建医科大学解剖学教研室的4个男性半盆腔尸体标本进行大体解剖观察；另选择2022年1-12月期间于福建医科大学附属协和医院结直肠外科行全直肠系膜切除术（TME）的16例直肠癌术后新鲜标本进行组织学观察。采用尸体标本大体解剖与术后新鲜标本组织学观察结合的方式进行研究。观察区域包括：（1）腹膜反折区直肠前方系膜形态和筋膜；（2）邓氏筋膜尾侧附着点；（3）盆丛和腹下神经前筋膜融合区；（4）直肠骶骨筋膜侧方附着缘；（5）直肠骶骨筋膜后方附着缘。 结果： （1）腹膜反折区直肠前方系膜形态和筋膜：直肠前方系膜呈三角形脂肪垫结构。底边向前跨越了腹膜反折最低点，邓氏筋膜起自三角形腹侧、腹膜反折前上方靠近膀胱侧的腹膜处，呈致密的筋膜结构。（2）邓氏筋膜尾侧附着点：邓氏筋膜向尾侧移行，于精囊腺、输精管壶腹和前列腺的交角处，与前列腺被膜紧密附着，其头侧见血管束穿经。（3）盆丛和腹下神经前筋膜的融合区：腹下神经前筋膜向腹侧与邓氏筋膜相移行，其中份与盆丛主体融合，不可分离，盆丛发出直肠支支配直肠。（4）直肠骶骨筋膜侧方和后方附着缘：直肠后方，直肠固有筋膜和腹下神经前筋膜相融合，形成直肠骶骨筋膜。融合筋膜向右侧分成两叶，外侧叶为腹下神经前筋膜，内侧叶为直肠固有筋膜。紧靠直肠系膜，沿着其向外发出筋膜的附着缘剪开，见直肠骶骨筋膜侧缘，与腹下神经前筋膜相连结。（5）术后新鲜标本组织学观察：腹膜反折区见腹膜的立方上皮，其最低点未见邓氏筋膜起源，腹膜反折腹侧见双层筋膜结构，邓氏筋膜呈较致密肥厚的胶原纤维结构，均从腹膜反折腹侧发出（16/16）；直肠固有筋膜呈较菲薄疏松的胶原纤维结构，直肠固有筋膜起源呈个体差异，16例中有13例与邓氏筋膜紧靠，共同从腹膜反折腹侧上方发出；有3例单独从腹膜反折最低点发出。邓氏筋膜尾侧断缘见双层筋膜结构，邓氏筋膜内多处S100着染。直肠骶骨筋膜后方断缘的尾侧为融合筋膜结构，高倍视野下，源自腹下神经前筋膜的胶原纤维间可清晰观察到粗壮的神经纤维结构。直肠骶骨筋膜侧方断缘向内发出的直肠固有筋膜的膜结构仍完整。 结论： 本研究发现，直肠前方系膜呈三角形脂肪垫结构。底边向前跨越了腹膜反折最低点，邓氏筋膜起自三角形腹侧、腹膜反折前上方靠近膀胱侧的腹膜处，并非起自腹膜反折最低点，这为术中从腹膜反折上1 cm切开、分离邓氏筋膜前间隙提供了依据。邓氏筋膜尾侧与前列腺被膜融合，融合区域可见丰富的神经血管束支配，并不存在前列腺后间隙的传统分离平面，这为从精囊腺底腹侧0.5 cm切开邓氏筋膜提供了依据。直肠后方直肠固有筋膜和腹下神经前筋膜融合，形成直肠骶骨筋膜（本质为融合筋膜）。融合筋膜在直肠两侧重新分成两叶，内侧叶为直肠固有筋膜，外侧叶为腹下神经前筋膜，向前移行为邓氏筋膜，且在两前侧外与盆丛主体发生致密融合。这为术中离断邓氏筋膜后从上向下（即从腹侧向尾侧）分离、离断腹下神经前筋膜、从而保护其外侧融合的盆丛和腹下神经提供了理论依据。.