In recent years, the incidence of Inflammatory Bowel Disease (IBD) has been increasing in China, which poses great challenges and burdens to the medical community due to its unknown etiology, recurrence and incurability. Co-infection is one of the important causes in IBD development. IBD accompanied with Clostridium Difficile Infection (CDI) can significantly decrease the treatment efficiency, leading to increased surgical rate, increased mortality, prolonged hospital stay, and increased hospital costs. Recently, several Chinese clinical guidelines about IBD or CDI have been published, but these guidelines are mainly based on the foreign studies. Compared with the developed countries, the lack of multi-center, large-scale and multi-test clinical trials and cohort studies caused limited understanding for IBD-CDI in China. Therefore, it is of great importance to carry out the multi-center clinical trials and analysis on IBD-CDI to improve the diagnostic and therapeutic efficiency in IBD-CDI patients

Objective:

1. To evaluate the prevalence rate of IBD-CDI in Chinese adults in China based on the multi-center clinical trials..
2. To analyze the related risk factors of IBD-CDI in China based on the multi-center clinical trials.
3. To analyze the intestinal flora of IBD-CDI patients via high-throughput sequencing.

Inclusion Criteria:

• 1.Inpatients with diagnostic criteria for ulcerative colitis and Crohn's disease in accordance with the consensus opinion on the diagnosis and treatment of inflammatory bowel disease in China in 2012
• 2.Willing to participate in the study;
• 3. Have the ability to understand and sign informed consent.

Exclusion Criteria:

• 1.Patients with infectious enteritis, intestinal tuberculosis, lymphoma, Behcet's disease or other intestinal diseases except inflammatory bowel disease;
• 2.Pregnant or lactating women;
• 3.Severe circulatory system, respiratory system, blood system, immune system, urinary system and other combined diseases or serious psychosomatic diseases.

The population will be selected from six hospital in China.