Longitudinal prospective monocentric observational study in which patients to start Mirikizumab for normal clinical practice will be followed for 24 weeks. Based on the findings in the comparison between US (IUS and TPUS) and endoscopy, the study aim is to build up a modified MUC (Milan Ultrasound Criteria) scoring system taking each colonic segment and the rectum into account, developing non-invasive quantitative ultrasound-based criteria to identify patients with active UC and assess its severity.

Inclusion Criteria:

• Age ≥ 18 years

• Confirmed diagnosis of UC according to ECCO guidelines

• Patients with active moderate-to-severe disease defined as MES

  ≥ 2

• Patients undergoing advanced therapies with mirikizumab according to clinical judgement

• Patients who provide written informed consent

Exclusion Criteria:

• Age < 18 years
• Patients with unclassified colitis or other gastrointestinal conditions
• Patients with current infections or other severe comorbidity, including liver, kidney or cardiac failure, which contraindicate the initiation of advanced therapy
• Patients unable or unwilling to provide consent

The study population is a population of adult patients with confirmed diagnosis of UC according to ECCO guidelines with an active moderate-to-severe disease defined as MES ≥ 2 and who have indication to undergo advanced therapies with mirikizumab according to clinical judgement