In this retrospective cohort study, data were collected from patients who underwent laparoscopic radical resection of SCC at Department of Gastrointestinal Surgery, People’s Hospital of Deyang from January 2017 to June 2021.

The inclusion criteria were as follows: (1) complete clinicopathological data, (2) preoperative colonoscopy or intraoperative exploration of tumor located in sigmoid colon, and (3) adenocarcinoma confirmed by postoperative pathology.

The exclusion criteria included the following: (1) preoperative radiotherapy or chemotherapy, (2) tumor invading surrounding tissues and organs or distant metastasis, (3) intraoperative conversion to open surgery, (4) severe organ diseases, such as those of heart, lung, liver, and kidney, or hematopoietic and endocrine diseases that may affect survival, (5) complication with severe infection, intestinal obstruction, or other malignant tumors; (6) history of previous abdominal surgery.

Based on SRA preservation, the patients were divided into the SRA preservation (n = 84) and control (n = 123) groups. The control group underwent conventional high ligation of the IMA root. All patient data, including age, gender, body mass index (BMI), operation time, intraoperative blood loss, tumor stage, the number of lymph nodes dissected, tumor differentiation, postoperative adjuvant chemotherapy, and postoperative exhaust and defecation times, were recorded in the database. Postoperative complications, mortality (30 days after surgery or before hospital discharge), and survival were also recorded (Figure 1).

Patients were laid in head-down lithotomy position. The peritoneal cavity was routinely explored. The peritoneum was opened on the right side of the IMA root, and the mesenteric membrane was separated upward along the space between Gerota's and Toldt's fascias. In the preservation group, the lymphoid adipose tissue at the root of IMA was dissected, and the IMA root was exposed. Then, the lymphatic adipose tissue around IMA was dissected along the direction of IMA, and the IMA vascular sheath was not opened routinely. The left colic artery and first or second sigmoid artery were divided and cut off along the IMA vascular sheath, and the SRA was preserved (Figures 2A,B). In addition to SRA, the left colic artery or inferior mesenteric vein (IMV) was selectively preserved in several patients, especially those with long sigmoid colon (Figures 2C,D). In the control conventional operation group, high ligation was performed at the roots of IMA and IMV roots (Figures 2E,F, respectively). Both groups followed the principle of complete mesocolic excision and 10 cm proximal and distal margin, and the inferior mesenteric plexus and hypogastric plexus were carefully protected. Before anastomosis, the bowels were fully freed to ensure that the anastomosis was free of tension.

AL after colorectal resection is defined as the defect of intestinal wall integrity at the colorectal or colo-anal anastomosis site (including suture and staple lines of neorectal reservoirs), leading to a communication between intra- and extraluminal compartments. A pelvic abscess close to the anastomosis is also considered AL. The severity grading of AL is as follows: Grade A: AL requiring no active therapeutic intervention; Grade B: AL requiring active therapeutic intervention but manageable without re-laparotomy; Grade C: AL requiring re-laparotomy (8).

Postoperative ileus (POI) was diagnosed if two or more of the following criteria were met on or after postoperative day 4: absence of flatus for over 24 h, absence of stool for over 72 h, abdominal distension, nausea or vomiting, incapability to tolerate diet in the past 24 h; clinical and imaging examinations (including x-ray radiograph, sonography, and computed tomography) indicative of POI (9).

Survival was measured from the time of surgery until death or last-known follow-up (censor date was January 1, 2022). The data were presented as mean ± standard deviation, and Chi-squared test or Fisher's exact test, analysis of variance, or group t test was conducted to test for differences between groups. Kaplan–Meier method was used for survival analysis, and log-rank test was applied for comparison of differences in survival curves. p < 0.05 was considered statistically significant. All statistical analyses were performed using the software SPSS Version 25.0.

The procedures of this study were in accordance with the Declaration of Helsinki and approved by the Ethics Committee of People's Hospital of Deyang (No.2022-04-051-K01).

A total of 207 patients with SCC were enrolled in this study. Exactly 84 patients underwent D3 lymph node dissection with preservation of SRA (SRA preservation group), and 123 patients underwent high ligation of the IMA (control group). Table 1 shows the comparison of clinicopathological factors between SRA preservation and control groups. No significant differences were observed in gender, age, BMI, intraoperative blood loss, tumor stage, tumor differentiation, the number of lymph nodes dissected, and postoperative adjuvant chemotherapy (p > 0.05). However, given the anatomy of IMA branches and SRA preservation, the operation time was significantly longer in the preservation group (p < 0.001) (Tables 1, 2).

The postoperative exhaust and defecation times of the SRA preservation group were significantly shorter than those of the control group, and the differences were statistically significant (p = 0.003; p < 0.001) (Table 2). Two cases of POI were observed in the control group, but the difference was not statistically significant compared with that in the preservation group (p = 0.652). Four cases of AL were detected in the control group and none in the preservation group, but the difference was not statistically significant (p = 0.248). No postoperative abdominal bleeding, lymph leakage, death, nor reoperation occurred in the two groups after surgery (Table 2).

The cumulative 1-, 2-, 3-, and 4-year overall survival rates were 88.7%, 80.4%, 71.7%, and 67.3%, respectively. No significant difference was observed in the overall survival and disease-free survival between the two groups (p = 0.436; p = 0.414) (Figures 3, 4, respectively).

Univariate analysis revealed that adjuvant chemotherapy (p < 0.001) was significantly associated with overall survival. Factors that may affect patient survival were further included in multivariate analysis through the Cox proportional risk model. Multivariate analysis demonstrated that tumor stage (p = 0.015) and adjuvant chemotherapy (p = 0.001) remained independently associated with overall survival. Adjuvant chemotherapy was a protective factor affecting the survival of patients [hazard ratio (HR) = 0.257, 95% confidence interval (CI) (0.119, 0.553, p = 0.001], and tumor stage was an adverse factor [HR = 4.2278, 95% CI (1.316, 13.586), p = 0.015]. However, SRA preservation was not an independent prognostic factor in this cohort (Table 3).