Faecal microbiota transplantation may improve symptoms of irritable bowel syndrome (IBS), according to a study in the Lancet Gastroenterology and Hepatology.

Roughly 90 patients with moderate-to-severe, diarrhoea-predominant IBS and abdominal pain at least weekly were randomised to receive either a fresh or frozen faecal microbiota transplantation from donor stool or a placebo transplant (their own frozen stool) via colonoscopy.

The primary outcome — symptom relief 3 months after transplantation — significantly favoured active transplantation over placebo (65% vs. 43% of participants).

A commentator says that five patients would need to be treated for one patient to see significant symptom relief. However, the between-groups difference was no longer significant after 12 months.

The commentator cautions that the primary outcome "was not one that would be accepted" by regulatory agencies. In addition, whether the treatment affected patients' faecal microbiota is not reported.