左原始后腹膜的解剖观察及其在术中左结肠后间隙分离时的临床意义

Anatomical observation of the left parietal peritoneum and its clinical significance in left retro-mesocolic space dissection

目的对左结肠后间隙分离时左原始后腹膜的走行进行活体和尸体标本解剖观察。方法采用描述性病例系列研究的方法。(1)回顾性收集2018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腹腔镜结直肠癌根治术(完整脾曲结肠游离)的35例非连续患者的手术录像,对录像中的左结肠后间隙分离过程进行观察,对同期科室数码数据库的5例直肠癌根治术后标本照片进行分析;(2)前瞻性纳入该科室2020年6月手术的4例直肠癌根治术后标本进行观察;(3)纳入来源于福建医科大学解剖学教研室的5具腹部尸体标本,其中男性3例,女性2例,进行解剖观察,并选取腹部尸体标本中3个未分离区域,即肠系膜下动脉(IMA)根部、内侧区域和外侧区域(含肾组织)进行Masson染色组织学观察研究。结果(1)35例手术录像观察结果:从外侧入路或中央入路分离左结肠后间隙时,有27例(77.1%)可观察到明显的"错层现象"和典型的左原始后腹膜结构,其表现为一层内外侧入路之间的筋膜屏障,为一层致密半透明结缔组织筋膜,脾曲结肠完全游离后见左原始后腹膜断端向头侧延续。(2)4例直肠癌根治术后标本解剖观察结果:取左结肠系膜的标本背侧面进行观察,可见左原始后腹膜断缘,断缘外侧为裸露的左半结肠系膜背侧叶,向下移行为直肠固有筋膜。(3)5具腹部尸体标本解剖所见:分别经外侧入路和中央入路分离左结肠后间隙,遭遇筋膜屏障,其本质为左原始后腹膜与Gerota筋膜;从尸体标本横断面观察,并继续解剖左原始后腹膜,发现从外向内,可进一步将左原始后腹膜从左半结肠系膜背侧叶剥离下来,而从内向外则无法进一步剥离。(4)组织学验证结果:IMA主干区域未见明显筋膜结构,仅在其外侧观察到被肠系膜下丛左侧束反复穿经的Gerota筋膜;内侧区域含4层筋膜结构,分别为左半结肠系膜腹侧叶、左半结肠系膜背侧叶、左原始后腹膜和Gerota筋膜,其中在左半结肠系膜背侧叶和左原始后腹膜之间可见细小脉管;外侧区域可见部分肾组织和肾筋膜,高倍视野下在结肠系膜背面可见3层清晰的筋膜结构,分别为左半结肠系膜背侧叶、左原始后腹膜和Gerota筋膜。结论左原始后腹膜是左结肠后间隙分离过程中,外侧入路或中央入路之间出现"错层现象"的解剖学基础,由于中间入路分离的起始部位Gerota筋膜被肠系膜下丛分支反复穿经,导致该区域较为致密,容易沿着该区域直接进入Gerota筋膜深面,从而使分离平面过深。

Objective To investigate the anatomic characteristics of the left parietal peritoneum and its surgical implementation while dissecting in left retro-mesocolic space.Methods A descriptive case series research methods was used.(1)surgical videos of 35 patients who underwent laparoscopic radical resection(complete mobilization of splenic flexure)of colorectal cancer in Union Hospital of Fujian Medical University between January 2018 and December 2018 were reviewed;(2)four specimens after radical resection of rectal cancer performing in June 2020 were prospectively enrolled and reviewed;(3)five specimens of left parietal peritoneum from 5 cadaveric abdomen(3 males and 2 females)were enrolled and reviewed as well;Tissues of 3 unseparated regions,namely the root of the inferior mesenteric artery(IMA),the medial region and the lateral region(including kidney tissue),from above the 5 cadaveric abdominal specimens were selected to perform Masson staining and histopathological examination.Results(1)Surgical video observation:"Staggered layer phenomenon"and typical left parietal peritoneum was found in 77.1%(27/35)of patients when the left retro-mesocolic space was separated from the lateral and central approaches.The left parietal peritoneum presented as a rigid fascia barrier between the lateral and central approaches,which was a translucent dense connective tissue fascia.After the splenic flexure were completely mobilized,the left parietal peritoneum stump continued to the cephalic side.(2)Observation of 4 surgical specimens:The dorsal side of the left mesocolon specimen was studied,and the left parietal peritoneum stump edge was identified.The outside of the stump edge was the left hemicolon dorsal layer,which was continuously downward to the rectal fascia propria.(3)Cadaveric abdominal specimens:The left retro-mesocolic space was separated through lateral and central approaches,and the rigid fascia barrier,essentially the left parietal peritoneum and Gerota fascia,was encountered.Cross-section view showed that the left parietal peritoneum could be further detached from the dorsal layer of the left mesocolon from the outside,but could not be further detached from the inside out.(4)Histological examination:There was no obvious fascia structure in the IMA root region,while outside the IMA root region,the left bundle of inferior mesenteric plexus penetrating Gerota fascia was observed.There were 4 layers of fascias in the medial region,including the ventral layer of the left mesocolon,the dorsal layer of the left mesocolon,left parietal peritoneum and Gerota fascia.Small vessels were observed between the dorsal layer of the left mesocolon and the left parietal peritoneum.In lateral region,renal tissue and renal fascia were observed.Three layers of fascia structures were observed clearly under high power field,including the dorsal layer of the left mesocolon,left parietal peritoneum,and Gerota fascia.Conclusions The left parietal peritoneum is the anatomical basis of the"staggered layer phenomenon"from the lateral or central approaches during the separation of left retro-mesocolic space.The small vessels in the dissection plane are the anatomical basis of intraoperative microbleeding,which need pre-coagulation.The central part of Gerota fascia is penetrated by the branches of the inferior mesenteric plexus,which results in a relatively dense surgical plane.Thus,during the dissection through the central approach,it is easy to involve in wrong surgical plane by deeper dissection.