Alterations in Gut Microbiota After Upper Gastrointestinal Resections: Should We Implement Screening to Prevent Complications?

Background: Surgical procedures and alterations of the gastrointestinal (GI) tract increase the risk of small intestinal bacterial overgrowth (SIBO), which is associated with GI symptoms and complications that compromise postoperative recovery. However, the prevalence and clinical impact of SIBO after various upper GI surgical procedures remain poorly understood. Objective: This study aimed to evaluate the prevalence of SIBO after different types of upper GI surgery and to investigate the associated clinical factors. Methods: We conducted an observational study involving 157 patients with a history of upper GI surgery: Roux-en-Y gastric bypass (RYGB), laparoscopic single-anastomosis gastric bypass (OAGB), subtotal (STG) or total gastrectomy (TG), subtotal (SP)or total pancreatectomy (TP), cephalic duodenopancreatectomy (WR), and small bowel resection for Crohn's disease. A glucose-hydrogen breath test was performed, and demographic, clinical, and treatment-related data were collected. Statistical analyses included t-tests, non-parametric tests, ANOVA, and correlation analyses using R software. Results: At a median follow-up of 25.7 ± 18.1 months, 31% (48/157) of patients tested positive for SIBO. The highest prevalence was observed after RYGB and OAGB (43%), followed by TG (30%), STG (29%), TP/WR (28%), and Crohn's disease bowel resection (19%). No cases of SIBO were observed after SP. SIBO positivity was significantly associated with bloating and flatulence (p = 0.002), lactose intolerance (p = 0.047), systemic sclerosis (p = 0.042), T2D (p = 0.002), and exposure to adjuvant chemotherapy (p = 0.001) and radiotherapy (p = 0.027). In addition, the risk of SIBO increased proportionally with the duration of GI resection or exclusion (p = 0.013). Conclusions: In our study, the prevalence of SIBO after upper GI surgery was 31%, with the highest incidence (43%) observed in metabolic surgery patients. Importantly, adjuvant radio/chemotherapy was associated with an increased risk of SIBO, and extensive small bowel resection or exclusion was strongly associated with an increased risk of SIBO. Furthermore, the limitations of current diagnostic methods, which lack sufficient sensitivity and specificity, highlight the importance of early screening and standardization of diagnostic techniques to improve patient management and outcomes.