Why is it so difficult to evaluate faecal microbiota transplantation as a treatment for ulcerative colitis?

Faecal microbiota transplantation (FMT) has recently re-emerged as a viable therapeutic option for colonic disorders. Its efficacy has been proved in the treatment of Clostridium difficile infection which has encouraged research into the use of FMT for other disorders involving gut dysbiosis, such as ulcerative colitis (UC), a chronic inflammatory disease characterized by relapsing and remitting colonic inflammation. Although the FMT protocol for C. difficile treatment is well established, there are numerous additional factors to consider when applying FMT to treat inflammatory diseases. Various studies have attempted to address these factors but technical inconsistency between reports has resulted in a failure to achieve clinically significant findings. Case reports of FMT in UC have shown favorable outcomes yet demonstrating these effects on a larger scale has proved difficult. The following review aims to explore these issues and to analyze why they may be hindering the progression of FMT therapy in UC.