Gut Microbiota Dysbiosis and Risk of Venous Thromboembolism: A Systematic Review

Background: Gut microbiota dysbiosis has been proposed as a potential contributor to venous thromboembolism (VTE), although its clinical relevance remains uncertain. Methods: This review was conducted following the PRISMA 2020 guidelines. We conducted a systematic review of studies evaluating the association between gut microbiota dysbiosis and VTE. MEDLINE/PubMed, Web of Science, EMBASE, and Scopus were searched from the inception to February 2026. Observational studies and Mendelian randomization (MR) analyses assessing microbiota composition, dysbiosis, or related metabolites in relation to VTE were included. Risk of bias was assessed using established tools. Results: Thirteen studies were included (five observational and eight MR). Observational evidence showed heterogeneous findings. Microbial metabolites such as trimethylamine N-oxide and lipopolysaccharides were associated with prothrombotic profiles in some studies, but no consistent association with VTE risk or recurrence was observed. The differences in microbiota composition were reported, although based on small populations. MR analyses identified microbial taxa with potential protective or risk associations, but most findings were modest and not robust after multiple testing correction. Conclusions: Gut microbiota dysbiosis may contribute to VTE through inflammatory and metabolic pathways; however, current clinical evidence is limited and inconsistent. Further prospective studies are needed to clarify causality and clinical implications.