Informed Consent Obtained Before Surgery or Randomization

Objective: To evaluate the effects of the postbiotic preparation JK-5G on gastrointestinal function recovery (GI-2 time), gastrointestinal dysfunction, nutritional status, and safety in patients after surgery for malignant bowel obstruction. Design: A randomized, double-blind, placebo-controlled, exploratory clinical trial. Patients are randomized 1:1 within 24 hours after surgery. After meeting criteria for initiating enteral intake, they receive either JK-5G or placebo (one sachet three times daily) for 10 consecutive days, and are followed up to postoperative day 30. Study Population: Adult patients (18-80 years old) who undergo surgery for malignant mechanical bowel obstruction and are hemodynamically stable within 24 hours after surgery. Sample Size: A total of 80 patients (40 in the postbiotic group and 40 in the placebo group). A blinded review of variability will be conducted after 40 patients have completed the study. Primary Endpoint: Time from the end of surgery to GI-2 recovery, where GI-2 recovery is defined as the later of the following two events: first passage of stool/effective stoma output, and first tolerance of the target diet. Key secondary endpoints include daily I-FEED scores, incidence of prolonged postoperative ileus, achievement of nutritional targets, and safety events. Statistics and Timeline: The primary analysis will use a stratified Cox model (intention-to-treat principle). The study is planned to be conducted from September 2026 to February 2028.