Published online Jun 14, 2021. doi: 10.3748/wjg.v27.i22.2921
Peer-review started: February 5, 2021
First decision: March 29, 2021
Revised: April 3, 2021
Accepted: May 22, 2021
Article in press: May 22, 2021
Published online: June 14, 2021
Irritable bowel syndrome (IBS) affects about 12% of the global population. Although IBS does not develop into a serious disease or increase mortality, it results in a considerable reduction in the quality of life. The etiology of IBS is not known, but the intestinal microbiota appears to play a pivotal role in its pathophysiology. There is no effective treatment for IBS, and so the applied treatments clinically focus on symptom relief. Fecal microbiota transplantation (FMT), an old Chinese treatment, has been applied to IBS patients in seven randomized controlled trials (RCTs). Positive effects on IBS symptoms in various degrees were obtained in four of these RCTs, while there was no effect in the remaining three. Across the seven RCTs there were marked differences in the selection processes for the donor and treated patients, the transplant dose, the route of administration, and the methods used to measure how the patients responded to FMT. The present frontier discusses these differences and proposes: (1) criteria for selecting an effective donor (superdonor); (2) selection criteria for patients that are suitable for FMT; (3) the optimal FMT dose; and (4) the route of transplant administration. FMT appears to be safe, with only mild, self-limiting side effects of abdominal pain, cramping, tenderness, diarrhea, and constipation. Although it is early to speculate about the mechanisms underlying the effects of FMT, the available data suggest that changes in the intestinal bacteria accompanied by changes in fermentation patterns and fermentation products (specifically short-chain fatty acids) play an important role in improving the IBS symptoms seen after FMT. FMT appears to be a promising treatment for IBS, but further studies are needed before it can be applied in everyday clinical practice.
Core Tip: Irritable bowel syndrome (IBS) is a common gastrointestinal disorder. There is no effective treatment for IBS, but fecal microbiota transplantation (FMT) seems promising. Some randomized controlled trials (RCTs) have shown that FMT improved the symptoms and quality of life of IBS patients, but others have found no such effects. The discrepancies between the outcomes of these RCTs are due to the selection processes for the donor and treated patients, the dose of transplant used, and the route of administration. Further studies are needed to optimize the FMT conditions in IBS patients.