Objective To investigate the risk factors for anastomotic leakage after laparo-scopic lower anterior resection (LAR) of rectal cancer, and the application value of its risk assess-ment scoring model.

Methods The retrospective case-control study was conducted. The clinico-pathological data of 539 patients who underwent laparoscopic LAR of rectal cancer in 13 medical centers, including 248 cases in Renji Hospital of Shanghai Jiaotong University School of Medicine, 35 cases in Ningbo First Hospital, 35 cases in Changzhou Second People's Hospital, 32 cases in the First People's Hospital of Nantong, 32 cases in Linyi People's Hospital, 31 cases in Changzhou Wujin People's Hospital, 28 cases in Jiading District Hospital of Traditional Chinese Medicine, 27 cases in the First Hospital of Taizhou, 26 cases in Shanghai Pudong Gongli Hospital, 21 cases in the People's Hospital of Rugao, 11 cases in Central Hospital of Fengxian District, 7 cases in Ningbo Hangzhou Bay Hospital and 6 cases in Jiangsu jianhu People's Hospital, from January 2016 to November 2020 were collected. There were 157 males and 382 females, aged (62.7±0.5)years. Observation indicators: (1) follow-up; (2) risk factors for anastomotic leakage after laparoscopic LAR; (3) establishment of risk assessment scoring model for anastomotic leakage after laparoscopic LAR. Follow-up was conducted by outpatient examination or telephone interview. Patients were followed up at 1 week after discharge or 1 month after the operation to detect the anastomotic leakage. Measurement data with normal distribution were represented as Mean±SD, and measurement data with skewed distribution were represented as M(range). Count data were represented as absolute numbers or percentages, and comparison between groups was analyzed using the chi-square test. Univariate analysis was conducted using the chi-square test and multivariate analysis was conducted usong the Logistic regression model. The area under curve of receiver operating characteristic curve was used to estimate the efficiency of detecton methods. The maximum value of the Youden index was defined as the best cut-off value.

Results (1) Follow-up: 539 patients were followed up at postoperative 1 week and 1 month. During the follow-up, 79 patient had anastomotic leakage, with an incidence of 14.66%(79/539). Of the 79 patients, 39 cases were cured after conservative treatment, 40 cases were cured after reoperation (ileostomy or colostomy). (2) Risk factors for anastomotic leakage after laparoscopic LAR. Results of univariate analysis showed that sex, age, body mass index, smoking and/or drinking, tumor diameter, diabetes mellitus, hemoglobin, albumin, grade of American Society of Anesthesio-logists (ASA), neoadjuvant chemoradiotherapy, distance from anastomotic level to dentate line, the number of pelvic stapler, reinforced anastomosis, volume of intraoperative blood loss, placement of decompression tube, preservation of left colic artery, operation time and professional doctors were related factors for anastomotic leakage after laparoscopic LAR (χ²=14.060, 4.387, 5.039, 4.094, 17.488, 33.485, 25.066, 28.959, 34.973, 34.207, 22.076, 13.208, 16.440, 17.708, 17.260, 4.573, 5.919, 5.389, P<0.05). Results of multivariate analysis showed that male, tumor diameter ≥3.5 cm, diabetes mellitus, hemoglobin <90 g/L, albumin <30 g/L, grade of ASA ≥Ⅲ, neoadjuvant chemoradiotherapy, distance from anastomotic level to dentate line <1 cm, the number of pelvic stapler ≥3, non-reinforced anastomosis, volume of intraoperative blood loss ≥100 mL and no placement of decom-pression tube were independent risk factors for anastomotic leakage after laparoscopic LAR (odds ratio=2.864,3.043,12.556,7.178,8.425,12.895,8.987,4.002,3.084,4.393,3.266,3.224,95% confidence interval as 1.279‒6.411, 1.404‒6.594, 4.469‒35.274, 2.648‒19.459, 2.471‒28.733, 4.027‒41.289, 3.702‒21.777, 1.746‒9.171, 1.365‒6.966, 1.914‒10.083, 1.434‒7.441, 1.321‒7.867, P<0.05). (3) Establishment of risk assessment scoring model for anastomotic leakage after laparoscopic LAR. based on the results of univariate analysis, clinicopathological factors with χ²>20, χ²>10 and ≤20 or χ²≤10 were defined as scoring of 3, 2, 1, respectively. The cumulative clinicopatho-logical factors scoring ≥6 was defined as an effective evaluating indicator for postoperative anastomotic leakage. The risk assessment scoring model (6-321) for anastomotic leakage after laparoscopic LAR was established. The cumulative value ≥6 indicated high incidence of anastomotic leakage, and the cumulative value <6 indicated low incidence of anastomotic leakage.

Conclusions Male, tumor diameter ≥3.5 cm, diabetes mellitus, hemoglobin <90 g/L, albumin <30 g/L, grade of ASA ≥Ⅲ, neo-adjuvant chemoradiotherapy, distance from anastomotic level to dentate line <1 cm, the number of pelvic stapler ≥3, non-reinforced anastomosis, volume of intraoperative blood loss ≥100 mL and no placement of decompression tube are independent risk factors for anastomotic leakage after laparoscopic LAR. The risk assessment scoring model (6-321) is established according to the above results.The cumulative value ≥6 indicates high incidence of anastomotic leakage and the cumulative value <6 indicates low incidence of anastomotic leakage.