Within this study, the investigators aim to directly compare the value of endoscopic remission, histologic remission and barrier healing for predicting long-term disease behavior in a large cohort of clinically remittent IBD patients.

Mucosal healing is a key therapeutic goal in the management of patients with inflammatory bowel diseases (IBD) that is associated with favorable long-term disease outcome. In addition, histologic remission is an emerging endpoint and first data suggest that functional assessment of the integrity of the intestinal barrier, i.e. barrier healing, by confocal laser endomicroscopy (CLE) correlates to clinical disease behavior and outcome.

Within this study, the investigators will prospectively include IBD patients in clinical remission and assess endoscopic remission, histologic remission and barrier healing during baseline ileocolonoscopy. Participants will then be closely followed up in the IBD outpatient department of the University Hospital Erlangen every 4 to 8 weeks for participants under biological therapy and every 8 weeks for participants under conventional therapy. At each visit, clinical disease activity using the Mayo Clinical Score (MCS) and the Crohn's disease activity Index (CDAI), respectively, routine laboratory parameters and current and past medications will be recorded. Further, at each visit, major clinical events (MCE), defined as (i) disease flare; (ii) IBD-related hospitalization, (iii) IBD-related surgery, (iv) necessity for initiation of systemic steroids, immunosuppressants or biologics; (v) necessity for escalation of an existing biological therapy, will be recorded. The primary endpoint of this study is to comparatively assess the predictive values of barrier healing, endoscopic remission and histologic remission for predicting occurrence of MCE in IBD patients in clinical remission

Inclusion Criteria:

• patients with an established IBD diagnosis for at least 12 months duration
• IBD patients in clinical remission

Exclusion Criteria:

• patients with poor bowel preparation
• patients with total colectomy,
• patients with concomitant beta blocker therapy,
• patients with known allergy to fluorescein
• patients with a planned change in IBD-related pharmacotherapy

Consecutive patients with an established IBD diagnosis for at least 12 months duration presenting in clinical remission presenting at the Department of Gastroenterology of the University Hospital Erlangen will be prospectively included.