This study employs a prospective, single-center, interventional design to investigate the prognostic value of confocal endomicroscopy in assessing treatment response in ulcerative colitis (UC) patients receiving small molecules .

The study incorporates confocal endomicroscopy as an additional diagnostic modality for assessing barrier dysfunction and treatment response in UC patients. Confocal endomicroscopy enables real-time visualization of mucosal changes at a cellular level during endoscopy, potentially enhancing the detection of treatment response and mucosal healing.

Eligible patients will undergo baseline assessment, including clinical evaluation, partial Mayo score calculation, endoscopic evaluation, biopsies with histological evaluation and confocal endomicroscopy. Follow-up assessments will be conducted at 8 weeks and 6 months after initiating therapy with small molecules .

The study aims to enroll a sample size of 26 UC patients to pilot the feasibility and utility of confocal endomicroscopy in assessing barrier dysfunction and treatment response.

Inclusion Criteria:

1. Established diagnosis of UC since at least 12 weeks prior to inclusion
2. Age ≥ 18 years
3. Any gender/sex
4. Active disease consistent with indication to start with Small molecules (defined as Mayo endoscopic score (MES) ≥ 1, partial Mayo score ≥ 3 (with at least rectal bleeding score of 1 and bowel movements score of 1)
5. No contraindications to endoscopy or confocal exam
6. Ability to understand and to comply with the study procedure and sign an informed consent form

Exclusion Criteria:

1. Subjects with an endoscopic Mayo sub-score at baseline <2;
2. Pregnancy
3. Subjects with any contraindication to any study procedure (included fluorescein allergy).