In recent years, with the increasing understanding of the anatomy and physiological functions of the lower rectum, the biological behavior of rectal cancer tumors, advancements in new surgical technologies, and the application of comprehensive treatment methods, there has been growing emphasis on radical surgical procedures for low rectal cancer that balance oncological safety with anal function preservation. After undergoing total mesorectal excision for low rectal cancer and subsequent coloanal anastomosis, patients often face a high risk of anastomotic leakage and pelvic infection. Therefore, a protective ileostomy is usually performed to divert feces, providing a relatively low-perfusion environment conducive to healing for ultra-low coloanal anastomoses. In the event of an anastomotic leak, the protective stoma can mitigate infection and reduce the likelihood of secondary surgeries. Nevertheless, complications following protective ileostomy, such as dehydration, chronic renal failure, and parastomal hernia, occur at rates as high as 43% . Additionally, complications related to stoma reversal exceed 20% , all of which significantly impact patients' quality of life. Approximately one-fifth of patients with preventive stomas are unable to have their stomas reversed as planned, or may require lifelong stoma formation.

In 1961, Turnbull and Cutait independently reported surgical techniques involving transanal pull-through rectal resection and delayed manual coloanal anastomosis. From a certain perspective, this procedure is the safest reconstructive method, effectively reducing anastomotic leakage-related complications and avoiding the need for a protective stoma. In recent years, its clinical application in challenging rectal cases involving radiation proctitis, complex recto-vaginal/urethral fistulas, salvage surgeries for anastomotic leaks, and low-stage progressive rectal cancer has gained increasing attention and acceptance.In 2020, a multicenter randomized controlled study published in JAMA Surgery found that the delayed anastomosis group (avoiding protective stoma) did not increase the incidence of anastomotic leaks or other complications compared to the standard coloanal anastomosis plus ileostomy group, and exhibited comparable oncological and functional outcomes . Furthermore, a recent systematic review in 2022 included one randomized controlled trial and nine observational studies with a total of 1,743 patients. This study found that staged Turnbull-Cutait anastomosis was associated with a reduced rate of anastomotic leaks.

However, the aforementioned studies and systematic reviews on staged Turnbull-Cutait anastomosis were all based on total mesorectal excision (TME), and there is a paucity of data on postoperative anal function and quality of life following this procedure, necessitating further research. As an extreme sphincter-saving surgery, ISR is currently limited in widespread adoption due to the high incidence of postoperative complications and suboptimal functional outcomes associated with anastomoses located very close to the anal verge. To date, there is a lack of systematic studies applying the Turnbull-Cutait Pull-through anastomosis to ISR procedures. Therefore, it is highly worthwhile to conduct a multicenter prospective randomized controlled study to determine whether the modified Bacon procedure (transanal pull-through, delayed anastomosis) can serve as an effective alternative to ISR-coloanal anastomosis, achieving comparable or lower rates of postoperative complications, as well as equivalent oncological radicality and defecatory function. Such research is urgently needed in this largely unexplored field. If successfully conducted and achieving its objectives, this clinical study could provide highly valuable guidance for clinical practice. Existing reports on the application of the modified Bacon procedure in low rectal cancer are generally small-sample, single-center, retrospective studies with low levels of evidence. This study aims to provide higher-level evidence through a larger-sample, prospective, multicenter, randomized controlled design.