Small Intestinal Bacterial Overgrowth Following Gastrointestinal Cancer Surgery: Current Evidence and Future Perspectives.

Small intestinal bacterial overgrowth (SIBO) has recently gained increasing attention as a potential cause of postoperative gastrointestinal symptoms following gastrointestinal cancer surgery. Surgical procedures can disrupt normal gastrointestinal physiology through anatomical reconstruction, impaired motility, reduced gastric acid secretion, vagal nerve injury, and alterations in the gut microbiota, thereby predisposing patients to bacterial overgrowth. Although positive breath tests for SIBO have frequently been reported after esophageal, gastric, and colorectal cancer surgery, the reported positivity rates vary widely because of differences in patient selection, surgical procedures, and diagnostic methods. Importantly, several studies evaluated selected symptomatic or referred patients; therefore, these rates should not necessarily be interpreted as the true prevalence of SIBO in the overall postoperative population. Breath testing is widely used because of its simplicity and non-invasive nature; however, altered gastrointestinal anatomy and accelerated postoperative transit may affect test specificity and potentially produce false-positive results. Evidence regarding treatment specifically in patients after gastrointestinal cancer surgery remains limited, and most data regarding rifaximin and other therapeutic approaches are extrapolated from general SIBO populations. This review summarizes the current evidence regarding the epidemiology, pathophysiology, diagnosis, and treatment of SIBO following gastrointestinal cancer surgery. We discuss future perspectives, including standardization of diagnostic criteria, optimization of breath testing, microbiome-based approaches, refinement of rifaximin therapy, and strategies for recurrence prevention. A better understanding of SIBO may improve the recognition and management of postoperative gastrointestinal symptoms and nutritional abnormalities; however, whether SIBO-directed management improves body composition, treatment tolerance, postoperative recovery, or long-term outcomes remains to be established.