Bowel Stimulation Before Loop Ileostomy Closure Using Probiotics: Study Protocol for a Randomized Controlled Trial at a Single Center.

Background: Low anterior resection syndrome (LARS) is a common functional problem after sphincter-preserving rectal cancer surgery and includes urgency, frequent bowel movements, clustering, and fecal incontinence. Diverting ileostomy may further disrupt the intestinal environment and alter the gut microbiota, potentially worsening bowel dysfunction after ileostomy closure. However, evidence remains limited on whether bowel stimulation with probiotics before ileostomy closure can improve postoperative bowel function and reduce LARS severity. Objective: This study aims to evaluate the safety, feasibility, and efficacy of probiotic bowel stimulation through the distal limb of a diverting ileostomy before ileostomy closure in patients with rectal cancer. Methods: This single-center randomized controlled trial will be conducted at Keimyung University Dongsan Medical Center, Republic of Korea. Eligible participants are adults aged 18-80 years with clinical stage II or III rectal adenocarcinoma who completed neoadjuvant chemoradiotherapy and underwent laparoscopic or robotic low anterior resection with total mesorectal excision and diverting ileostomy, and who are scheduled for elective ileostomy closure. Participants will be randomly assigned in a 1:1 ratio to receive either 250 mL of normal saline with 4 g of Lacidofil or 250 mL of normal saline alone via the distal limb of the ileostomy once daily for 2 weeks before closure. The primary outcome is the LARS score 3 months after ileostomy closure. Secondary outcomes include postoperative complications, bowel recovery, stool habits, laboratory findings, and length of hospital stay. Analyses will primarily follow the intention-to-treat principle. Results: The study was approved by the Institutional Review Board of Keimyung University Dongsan Medical Center (DSMC-2024-03-016) and registered with the Clinical Research Information Service (KCT0011052). Recruitment is planned to begin in March 2026 and is expected to continue through March 2029. At the time of manuscript submission, the study is in the pre-enrollment stage, with no participants recruited and no data analysis performed. Results are expected to be published in 2029. Conclusions: This trial will provide prospective evidence on whether probiotic bowel stimulation before ileostomy closure is a safe and effective strategy for improving postoperative bowel function and alleviating LARS in patients undergoing rectal cancer surgery with diverting ileostomy.