This study included two topics: one was to test the efficacy and safety of fecal microbiota transplants plus partial enteral nutrition (PEN) in refractory pediatric UC where conventional therapy has failed, and the other was to explore the efficacy and safety of FMT plus PEN as first-line therapy for pediatric active UC

Recent studies have suggested that gut imbalance and deregulation of immunological responses plays a pivotal role in the disease development of UC, and that FMT could be a useful treatment. In the refractory ulcerative colitis group, our study is aims to explore FMT plus PEN in the treatment of refractory pediatric UC. In the induction stage of UC, standard therapy remained unchanged, FMT and PEN treatment are added, and the investigators hope the withdrawal of conventional drug therapy was gradually reduced. Refractory UC is defined as refractory to standard therapy (e.g., steroids, immunomodulators, cyclosporine, tacrolimus, or anti-TNF agents).

As a first-line treatment group for UC, our study is aims to explore FMT plus PEN as a first-line treatment for active UC in children. participants treated with FMT coupled with PEN are defined as the FMT group, and those treated with PEN coupled with mesalazine served as the PEN group.

FMT treatment is given for at least one course of FMT treatment. If repeated FMTs are received, it is usually at a 2 month interval.

All the participants received PEN (80% of total calories as a polymeric diet, Peptamen, Nestle, Vevey, and Switzerland) intervention to help induce and maintain clinical remission.

Inclusion Criteria:

age of older than 2 years and younger than 16 years with no genetic diseases; as a first-line treatment group for UC, newly diagnosed with mild-to-moderate UC (defined by the PUCAI of >10 and≤64); In the refractory ulcerative colitis group, all refractory pediatric with mild-to-moderate UC (defined by the PUCAI of >10 and≤64) defined by children who failed conventional treatment (hormone, immunosuppressant, biologics); agree to received regularly colonoscopy

Exclusion Criteria:

Children who were treated by PEN (80%) less than 8 weeks; As a first-line treatment group for UC, patients who were treated with corticosteroids, methotrexate, thiopurines, and anti-TNF agents as their first-line treatment; Known contraindication to all FMT infusion method such as nasoduodenal tube insertion, oesophago-gastro-duodenoscopy (OGD), enteroscopy, colonoscopy, enema and Fecal capsule; Unwilling to give informed consent/ assent