The goal of this retrospective observational study is to obtain the spatial resolution of the entire intestinal fibrotic process through the technology STOmics Stereoseq. For this study we will use surgical specimens from 8 UC e 8 CD previously collected for the already approved project, IBD Biobank, and stored at -80° C.

This is a monocentric observational study in which we will use the biological material from surgery carried out for normal clinical practice, and already stored at -80°C.

This project has as purpose:

1. To unravel the changes in the intestine leading to complications in CD and UC patients. In particular, we aim to identify the cell populations, their spatial organization, interactions, and specific transcriptional shifts, leading the progression from healthy tissue to inflamed and from inflamed to fibrotic tissue. We will be interested in producing a profile of Spatial transcriptomics of all areas of the surgical specimen.
2. To compare the spatial organization and differential gene expression of tissue

Inclusion Criteria:

• adult patient (age ≥18 years), both male and female patients with histologically confirmed CD and UC undergoing intestinal resection according to standard of care due to complicating disease, regardless of their current or past medical treatment;
• patients that have signed the IBD Biobank informed consent and consented to the use of their own biological material in future study or pertaining to the same field of investigation.

Exclusion Criteria:

• - patients with unconfirmed both UC and CD diagnoses;
• patients with superimposed dysplasia or cancer diagnosis and resections for which post- operative endoscopic assessment of recurrence is not feasible;
• patients who have not signed the IBD Biobank informed consent.

Retrospective observational study involving patients with Crohn's disease (CD) (n=8) and patients with ulcerative colitis (UC)(n=8) who had undergone surgery according to the standard of care. We will use the biological material from surgery carried out for normal clinical practice, and already stored at -80°C for IBD Biobank project. The retrospective referral period of time goes from July 2022 until July 2023.