Inflammatory bowel diseases (IBD) are chronic inflammatory diseases. It is believed that the inflammation results from sustained abnormal immune response towards altered or pathogenic microbiota in genetically susceptible hosts. Malnutrition is common in IBD, especially in pediatric Crohn's disease(CD). Exclusive enteral nutrion(EEN) has been shown to improve nutritional status and inflammatory markers in pediatric CD. But there is limited data about the effect of EEN on Chinese children with CD. In this study, investigators focused on disease process,nutritional status and gut microbiome of Chinese children with newly-diagnosed CD after EEN treatment.

Inclusion Criteria:

• Pediatric CD patients who were newly diagnosed and being treated with EEN at the Children's Hospital of Fudan University

Exclusion Criteria:

• (1) patients who were administered corticosteroids, immunosuppressive drugs, or biological agents prior to the study; (2) patients who could not finish the daily prescribed volume of formula for any reason; (3) patients who could not attend consecutive follow-up sessions; (4) patients who had received antibiotics or probiotics within 1.5 months prior to the study; and (5) patients who had been given corticosteroids, immunosuppressive drugs, biological agents, antibiotics, or probiotics during the EEN process.