The Prediction of Postoperative Anorectal Dysfunction after Low Anterior Resection for Lower Rectal Cancer by Measuring the Volume of Defecation-Related Muscles.

Purpose Approximately 90% of patients are thought to develop bowel dysfunction after low anterior resection (LAR). Although some prognostic factors have been reported, the volumes of defecation-related muscles have not been examined. This retrospective study investigated the association between the preoperative volume of defecation-related muscles and major LARS. Methods Forty-six patients who underwent LAR for rectal cancer between 2013 and 2020 in our institution were analyzed. They had no local residual tumor or local recurrence at the time of the study and no problems with their defecation function pre-operatively. Defecation-related muscle volume measurements were made before surgery, and the patients answered a low anterior resection syndrome (LARS) score questionnaire after surgery. The muscle volume was adjusted by the patient’s height squared. Results Twenty-seven patients (58.7%) developed major LARS. In the univariate analysis, sex, lateral lymph node dissection, and diverting ileostomy as well as muscle volume of the external anal sphincter, pubococcygeal + iliococcygeus muscle, and puborectal muscle were associated with major LARS. In a multivariate analysis, pubococcygeal + iliococcygeus muscle (< 5.96 ml/m 2 ) was the only factor ( p = 0.02). Conclusions Measuring the volume of the defecation-related muscles may aid in predicting major LARS.