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 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 treatment is well established, there are numerous additional factors to consider when applying FMT to treat inflammatory diseases.