Crohn's disease (CD) is an incurable chronic inflammatory disorder of the gastrointestinal tract. Ulcerative colitis (UC) is an idiopathic, chronic, inflammatory disease affecting the colon. This study will assess the (long-term) effectiveness and safety of upadacitinib in real-world clinical practice in adult participants with moderate to severe ulcerative colitis (UC) and crohn's disease (CD).

Upadacitinib is an approved drug for treating ulcerative colitis (UC) and Crohn's disease (CD). Approximately 280 participants who are prescribed Upadacitinib by their physician in accordance with local label will be enrolled in 8 sites across Belgium.

Participants will receive upadacitinib as prescribed by their physician according to their routine clinical practice and local label. Participants will be followed for up to 3 years.

There is expected to be no additional burden for participants in this trial. Participants will attend regular visits during the study at a hospital or clinic according to their routine clinical practice

Inclusion Criteria:

• Participants with a diagnosis of moderate to severe Crohn's disease or Ulcerative colitis, initiated with upadacitinib at least 12 months prior to inclusion, including participants that were initiated on upadacitinib, but later (i.e. at the moment of data collection) discontinued, or switched to another treatment.
• Participants initiating commercially available upadacitinib at the clinician's discretion as part of their routine clinical care; the decision to administer upadacitinib must be made prior to and independent of recruitment into the study
• Participants prescribed upadacitinib in accordance with the approved local label and treatment recommendations

Exclusion Criteria:

• Participants previously exposed to upadacitinib in a clinical trial or early access program
• Participants participating in interventional research (not including non-interventional
• Participants with stoma

Adult participants with ulcerative colitis or Crohn's Disease