Background: Bacteria and other microorganisms that live in the intestines (the gut microbiome) play an important role in a person s health. The gut microbiome helps to regulate the immune system and control inflammation. Imbalances in the gut microbiome have been linked to illnesses such as inflammatory bowel disease (IBD). People diagnosed with IBD can have serious health problems. Researchers want to know more about how the gut microbiome affects the development and progression of IBD in children. In this natural history study, they will compare the gut microbiomes of healthy children with those who have IBD.

Objective: To collect stool and samples of intestine tissue from children with and without IBD undergoing colonoscopy.

Eligibility: People under 21 years old who are having a colonoscopy at the Inova Health System or Pediatric Specialists of Virginia.

Design: Participants will fill out a questionnaire. They will answer questions about their history. Topics may include how they were fed as infants; how they were born; and how often they took antibiotics. Stool and tissue samples from the intestines will be taken during the participants colonoscopy. They may also give samples of blood and urine. Participants may be asked to provide additional stool, blood, and urine samples. They may do this up to 3 times per year. These samples may be collected at the clinic; they may also be collected at home and mailed to the researchers. If they have more colonoscopies, participants may be asked for more tissue samples. Participants will be enrolled for up to 10 years. ...