Postoperative gut dysbiosis and its clinical implications, with an emphasis on probiotic strategies in gastric cancer patients undergoing gastrectomy: a narrative review

Purpose: This review explores alterations in gut microbiota following gastrointestinal surgery, with a focus on gastrectomy for gastric cancer, and evaluates the therapeutic potential of probiotics in restoring microbial balance and reducing postoperative complications, including infections, inflammation, immune dysfunction, and cancer recurrence.Current concept: Gastrointestinal surgery disrupts gut microbial homeostasis via surgical stress, oxygen exposure, altered bile flow, and perioperative antibiotic use. Gastrectomy, in particular, induces marked changes in the microbiota, including increased oral-origin and aerotolerant bacteria, decreased short-chain fatty acid–producing species, and elevated bile acid-transforming organisms. These alterations contribute to complications such as small intestinal bacterial overgrowth, surgical site infections, postoperative ileus, nutrient malabsorption, and potentially a higher risk of colorectal cancer. Probiotics—especially strains of Lactobacillus, Bifidobacterium, and Clostridium—have demonstrated beneficial effects by modulating the gut ecosystem, enhancing epithelial barrier integrity, and regulating immune and metabolic pathways. Randomized clinical trials support using probiotics in improving gastrointestinal recovery, reducing systemic inflammation, restoring microbial diversity, and shortening hospital stays after gastrectomy. Multi-strain probiotic formulations, particularly when administered perioperatively, show the greatest promise. However, safety concerns remain, especially for immunocompromised or critically ill patients, underscoring the need for rigorous clinical oversight and adherence to regulatory standards such as the European Food Safety Authority’s Qualified Presumption of Safety guidelines.Conclusion: Postoperative dysbiosis is a modifiable factor in adverse surgical outcomes. Probiotic supplementation offers promising therapeutic potential in patients undergoing gastrectomy, though optimal strains, dosing, and timing remain to be determined. Tailored, evidence-based strategies may ultimately enhance both recovery and long-term outcomes after gastric cancer surgery.