目的:不少外科医生对结肠脾曲的肠系膜形态认识不足，以致于在进行脾曲周围癌的完整系膜切除时存在诸多问题。本研究对结肠脾曲游离过程中的肠系膜形态进行连续的活体解剖观察，并从胚胎学角度，对结肠脾曲特有的肠系膜形态进行三维重建，以帮助外科医生进一步理解该区域的系膜结构。方法:回顾性收集2018年1月至2019年6月期间，就诊于福建医科大学附属协和医院结直肠外科的9例录像完整、质量合格的非连续患者的临床病理资料和手术录像。全组患者均由同一组外科医师实施腹腔镜下左半结肠癌根治术，以中间入路为主的“三路包抄”方式进行脾曲游离。在脾曲游离过程中，对横结肠系膜和降结肠系膜形态进行观察，结合胚胎学理论进行三维模拟。以胰腺腹侧尾侧缘为轴向，并连续采集4个层面的术中照片（切面1、2、3、4）。结果:脾曲游离过程的中位手术时间为31（12~55）min，中位出血量5（2~30）ml，术中1例患者出现脾下极血管损伤，予超声刀电凝止血成功。9例患者均观察到稳定的横结肠系膜根结构；横结肠系膜根位于胰腺下缘，内侧较为明显且坚韧，而在胰体尾部该结构逐渐消失，代之以光滑的相互移行的横结肠系膜和降结肠系膜背侧叶。通过术中观察重建结肠脾曲形态：胚胎时期横结肠系膜呈扇形移行为降结肠系膜，在其内侧（切面1至切面2），横结肠系膜和降结肠系膜移行处受肠系膜上动脉（SMA）的牵拉而内翻，发生对折，并受胰腺的压榨，从而形成术中观察到的横结肠系膜根结构；其外侧（切面3至切面4）远离SMA的力学牵拉，移行区未受胰体尾压榨，横结肠系膜和降结肠系膜移行处结肠系膜背面光滑，平躺于相对应的由胰体尾、Gerota筋膜和脾下极构成的膜床上。结论:本研究从胚胎学角度，对结肠脾曲特有的肠系膜形态进行三维模拟，提出了能稳定在术中观察到的横结肠系膜根结构。术中以胰腺腹侧尾侧缘为轴向，平Gerota筋膜水平，由内向外切断横结肠系膜根至胰体尾下缘，可保证横结肠系膜根部脂肪和淋巴组织的完全清扫。“,”Objective:At present, surgeons do not know enough about the mesenteric morphology of the colonic splenic flexure, resulting in many problems in the complete mesenteric resection of cancer around the splenic flexure. In this study, the morphology of the mesentery during the mobilization of the colonic splenic flexure was continuously observed in vivo, and from the embryological point of view, the unique mesenteric morphology of the colonic splenic flexure was reconstructed in three dimensions to help surgeons further understand the mesangial structure of the region.Methods:A total of 9 patients with left colon cancer who underwent laparoscopic radical resection with splenic flexure mobilization by the same group of surgeons in Union Hospital of Fujian Medical University from January 2018 to June 2019 were enrolled. The splenic flexure was mobilized using a “three-way approach” strategy based on a middle-lateral approach. During the process of splenic flexure mobilization, the morphology of the transverse mesocolon and descending mesocolon were observed and reconstructed from the embryological point of view. The lower margin of the pancreas was set as the axis, and 4 pictures for each patient (section 1-section 4) were taken during middle-lateral mobilization.Results:The median operation time of the splenic flexure mobilization procedure was 31 (12-55) minutes, and the median bleeding volume was 5 (2-30) ml. One patient suffered from lower splenic vessel injury during the operation and the bleeding was stopped successfully after hemostasis with an ultrasound scalpel. The transverse mesocolon root was observed in all 9 (100%) patients, locating under pancreas, whose inner side was more obvious and tough, and the structure gradually disappeared in the tail of the pancreatic body, replaced by smooth inter-transitional mesocolon and dorsal lobes of the descending colon. The mesenteric morphology of the splenic flexure was reconstructed by intraoperative observation. The transverse mesocolon was continuous with a fan-shaped descending mesocolon. During the embryonic stage, the medial part (section 1-section 2) of the transverse mesocolon and the descending mesocolon were pulled and folded by the superior mesenteric artery (SMA). Then, the transverse mesocolon root was formed by compression of the pancreas on the folding area of the transverse mesocolon and the descending mesocolon. The lateral side of the transverse mesocolon root (section 3-section 4) was distant from the mechanical traction of the SMA, and the corresponding folding area was not compressed by the tail of the pancreas. The posterior mesangial lobe of the transverse mesocolon and the descending mesocolon were continuous with each other, forming a smooth lobe. This smooth lobe laid flat on the corresponding membrane bed composed of the tail of pancreas, Gerota's fascia and inferior pole of the spleen.Conclusions:From an embryological point of view, this study reconstructs the mesenteric morphology of the splenic flexure and proposes a transverse mesocolon root structure that can be observed consistently intraopertively. Cutting the transverse mesocolon root at the level of Gerota's fascia can ensure the complete resection of the mesentery of the transverse colon.