The purpose of this study is to characterize which patients with Crohn's disease are likely to respond to standard of care to vedolizumab therapy.

Inclusion criteria:

1. Male or Female ≥18 and ≤70 years old.

2. Patients must be appropriate for baseline colonoscopy prior to induction therapy with vedolizumab.

3. Patients must have active inflammatory disease as seen by colonoscopy. 3A-Adult patients with moderately to severely active UC who have:

   1. had an inadequate response with, lost response to, or were;

   2. intolerant to a tumor necrosis factor (TNF) blocker or;

   3. immunomodulator; or had an inadequate response with, were;

   4. intolerant to, or demonstrated dependence on corticosteroids:

      • inducing and maintaining clinical response
      • inducing and maintaining clinical remission
      • improving endoscopic appearance of the mucosa
      • achieving corticosteroid-free remission 3B-Adult patients with moderately to severely active CD who have

   1. had an inadequate response with, lost response to, or were

   2. intolerant to a TNF blocker or immunomodulator; or had an

   3. inadequate response with, were intolerant to, or demonstrated

   4. dependence on corticosteroids:

      • achieving clinical response
      • achieving clinical remission
      • achieving corticosteroid-free remission

4. Patients will also have biochemical analysis with CRP and fecal calprotectin prior to initiating treatment with vedolizumab.

Exclusion criteria:

1. Patients that will not undergo colonoscopy at baseline prior to treatment with vedolizumab.
2. Patients who do not have endoscopic or biochemical (CRP, calprotectin) evidence of inflammation.
3. Patients that have been on natalizumab within 12 weeks of beginning vedolizumab.
4. Previous treatment with cyclosporine, thalidomide, or investigational drugs within 30 days of enrollment, prior treatment with vedolizumab
5. Toxic megacolon
6. Abdominal abscess
7. Symptomatic colonic stricture
8. Stoma
9. Increased risk of infection (eg, active or latent tuberculosis, immunodeficiency) Other clinically meaningful laboratory abnormalities: pregnancy or lactation, an unstable or uncontrolled medical disorder, colonic dysplasia or adenomas, and malignant neoplasms.

Participants being seen at the University of Miami IBD clinics with a diagnosis of CD or UC and about to initiate standard of care treatment with vedolizumab.