Low anterior resection syndrome (LARS) occurs in approximately 80% of patients after sphincter-preserving surgery for low rectal cancer, causing defecatory dysfunction and social difficulties. Its pathogenesis remains unclear. This article discusses two major factors: impaired neorectal motility due to disruption of autonomic nerves to the proximal colon and anal dysfunction from nerve injury to the remaining rectum and internal anal sphincter. Additionally, the rectosigmoid brake, a colonic region involved in continence and potentially affected by rectal cancer surgery, may contribute to LARS. Its role warrants further investigation.