摘要目的:初步探讨左半结直肠癌合并降结肠系膜旋转不良（PDM）的解剖形态与分型，并探究应用腹腔镜根治手术的安全性。方法:本研究为描述性病例系列研究。回顾性分析2021年7月至2022年9月间，福建医科大学附属协和医院结直肠外科数据库中实施腹腔镜根治手术的995例左半结肠和直肠癌患者的临床资料，对其中24例（2.4%）合并PDM者回顾影像学资料和手术录像，观察降结肠及系膜分布形态，评估腹腔镜根治手术的可行性和并发症。根据解剖学形态特点，将PDM分型如下：0型为PDM合并中肠旋转不良或升结肠系膜旋转不良；1型为横结肠与降结肠移行处系膜未固定；2型为PDM降结肠在肠系膜下动脉水平附近明显内移，其中不越过腹主动脉者为2A型，越过腹主动脉者为2B型；3型为降乙交界结肠系膜未固定，在肠系膜下动脉水平以下明显内移。结果:24例术中诊断左半结直肠癌合并PDM患者中，仅有9例（37.5%）术前影像被部分外科医师阅片时发现并诊断。全组患者男性22例，女性2例；年龄为（63±9）岁。24例PDM分型如下：0型占4.2%（1/24）；1型占8.3%（2/24）；2A型和2B型分别占37.5%（9/24）和25.0%（6/24）；3型占25.0%（6/24）。全组患者均存在结肠系膜自身粘连并行松解，20例（83.3%）存在结肠与回肠系膜粘连，12例（50.0%）游离脾曲。14例（58.3%）患者的肠系膜下动脉分支为全共干型。24例接受腹腔镜D 3手术，无中转开腹，其中22例（91.7%）保留肠系膜下动脉主干。术中发现2例（8.3%）患者近切端结肠缺血，均为肠系膜下动脉高位结扎者，其中1例为近肛管型低位直肠癌，因术前肛门功能差行经括约肌间腹会阴联合切除术；1例被迫行腹腔镜辅助结肠次全切除术。全组手术时间（260±100）min，中位出血量为50（20~200）ml，No.253淋巴结中位清扫数目3（0~20）枚，仅1例（4.2%）发生No.253淋巴结转移。术后中位住院时间8（4~23）d。术后并发症发生率16.7%（4/24），术后均未发生肠缺血坏死；1例（4.2%）ⅡA期直肠癌患者术后发生B级吻合口漏（Clavien-Dindo Ⅲ级），择期行回肠袢式造口，余均为Ⅰ~Ⅱ级。 结论:PDM常伴系膜粘连，该分型有助于腹腔镜手术中粘连松解时识别降结肠及系膜，术中应尽可能保护拟切端结直肠血供，以避免非计划性扩大结肠切除、Hartmann术或永久造口。

abstractsObjective:To investigate anatomical morphology and classification of persistent descending mesocolon (PDM) in patients with left-sided colorectal cancer, as well as the safety of laparoscopic radical surgery for these patients.Methods:This is a descriptive study of case series. Relevant clinical data of 995 patients with left colon and rectal cancer who had undergone radical surgery in Fujian Medical University Union Hospital from July 2021 to September 2022 were extracted from the colorectal surgery database of our institution and retrospectively analyzed. Twenty-four (2.4%) were identified as PDM and their imaging data and intra-operative videos were reviewed. We determined the distribution and morphology of the descending colon and mesocolon, and evaluated the feasibility and complications of laparoscopic surgery. We classified PDM according to its anatomical characteristics as follows: Type 0: PDM combined with malrotation of the midgut or persistent ascending mesocolon; Type 1: unfixed mesocolon at the junction between transverse and descending colon; Type 2: PDM with descending colon shifted medially (Type 2A) or to the right side (Type 2B) of the abdominal aorta at the level of the origin of the inferior mesentery artery (IMA); and Type 3: the mesocolon of the descending-sigmoid junction unfixed and the descending colon shifted medially and caudally to the origin of IMA.Results:The diagnosis of PDM was determined based on preoperative imaging findings in 9 of the 24 patients (37.5%) with left-sided colorectal cancer, while the remaining diagnoses were made during intraoperative assessment. Among 24 patients, 22 were male and 2 were female. The mean age was (63±9) years. We classified PDM as follows: Type 0 accounted for 4.2% (1/24); Type 1 for 8.3% (2/24); Types 2A and 2B for 37.5% (9/24) and 25.0% (6/24), respectively; and Type 3 accounted for 25.0% (6/24). All patients with PDM had adhesions of the mesocolon that required adhesiolysis. Additionally, 20 (83.3%) of them had adhesions between the mesentery of the ileum and colon. Twelve patients (50.0%) required mobilization of the splenic flexure. The inferior mesenteric artery branches had a common trunk in 14 patients (58.3%). Twenty-four patients underwent D3 surgery without conversion to laparotomy; the origin of the IMA being preserved in 22 (91.7%) of them. Proximal colon ischemia occurred intraoperatively in two patients (8.3%) who had undergone high ligation at the origin of the IMA. One of these patients had a juxta-anal low rectal cancer and underwent intersphincteric abdominoperineal resection because of poor preoperative anal function. Laparoscopic subtotal colectomy was considered necessary for the other patient. The duration of surgery was (260±100) minutes and the median estimated blood loss was 50 (20-200) mL. The median number of No. 253 lymph nodes harvested was 3 (0-20), and one patient (4.2%) had No.253 nodal metastases. The median postoperative hospital stay was 8 (4-23) days, and the incidence of complications 16.7% (4/24). There were no instances of postoperative colon ischemia or necrosis observed. One patient (4.2%) with stage IIA rectal cancer developed Grade B (Clavien-Dindo III) anastomotic leak and underwent elective ileostomy. The other complications were Grade I-II.Conclusions:PDM is frequently associated with mesenteric adhesions. Our proposed classification can assist surgeons in identifying the descending colon and mesocolon during adhesion lysis in laparoscopic surgery. It is crucial to protect the colorectal blood supply at the resection margin to minimize the need for unplanned extended colectomy, the Hartmann procedure, or permanent stomas.