Abstract: Objective  To analyze the influencing factors of poor anal function after laparoscopic intersphincteric resection(Lap-ISR) for extremely low rectal cancer,and to construct and verify a prediction model based on this model,in order to provide guidance for improving the anal function of patients with extremely low rectal cancer after Lap-ISR.Method  A total of 127 patients with extremely low rectal cancer who underwent Lap-ISR in Taizhou People’s Hospital from June 2020 to June 2022 were retrospectively selected.Patients were followed up for 12 months after surgery,and postoperative anal function was evaluated by the anal incontinence score(Wexner).According to Wexner score,the patients were divided into good anal function group(106 cases) and poor anal function group(21 cases).The clinical data of patients were collected and the risk factors affecting postoperative poor anal dysfunction were analyzed,and a Nomogram model was constructed to predict the risk of postoperative anal dysfunction in patients after Lap-ISR,and the receiver operating characteristic curve(ROC) was drawn.The area under the curve(AUC) was used to analyze the predictive efficacy of the prediction model for poor anal dysfunction after Lap-ISR.Result The incidence of anal dysfunction after Lap-ISR in patients with extremely low rectal cancer was 16.54%(21/127).Univariate analysis showed that there was no significant difference in gender,age,body mass index,clinical stage,combined underlying diseases,operation time,intraoperative blood loss,anastomosis method,and the distance from the lower edge of the tumor to the dentate line between the two groups(P>0.05).The proportion of tumor diameter≥5 cm,the proportion of neoadjuvant chemotherapy,the distance between anastomosis and anal verge<2 cm,and the proportion of anastomotic leakage in the anal dysfunction group were higher than those in the good anal function group(P<0.05).Cox multivariate regression analysis showed that tumor diameter≥5 cm(OR=5.124),neoadjuvant chemotherapy(OR=5.761) and anastomotic leakage(OR=6.881) were risk factors for postoperative anal function(P<0.05).Wexner score of patients with tumor diameter ≥5 cm was higher than that of patients with tumor diameter < 5 cm,Wexner score of patients with neoadjuvant chemotherapy was higher than that of patients without neoadjuvant chemotherapy,and Wexner score of patients with anastomotic leakage was higher than that of patients without anastomotic leakage(P<0.05).Internal validation of Bootstrap method showed that the C-index was 0.785(95%CI: 0.692~0.851).The results of ROC curve showed that the sensitivity and specificity of the nomogram model in predicting postoperative poor anal function of patients were 85.70% and 88.70%,respectively,and the AUC was 0.895(95%CI: 0.795~0.984).Conclusion Tumor diameter,neoadjuvant chemotherapy and anastomotic leakage are risk factors for poor anal function after Lap-ISR in patients with extremely low rectal cancer.The nomogram risk prediction model based on the above risk factors has a good risk efficiency in evaluating the risk of postoperative anal dysfunction in patients.

Key words: extremely low rectal cancer, laparoscopic intersphincteric resection, anal function, influence factor, risk prediction model, nomogram