The association between IBD and kidney diseases is more common than previously thought. However, the data is limited and comes from studies with small sample sizes. The proposed study aims to investigate this association in a large population of patients with IBD, assessing risk factors and potential changes in the therapeutic approach to minimize the risk of kidney damage.

The primary objective of this study is to characterize the association between IBD and kidney diseases, as well as the progression of intestinal disease and kidney function in patients who have undergone transplantation.

The study is monocentric, observational, and both retrospective and prospective.

All patients who agree to participate in the study and sign the informed consent will be asked to allow the collection of their clinical data for database compilation. Retrospective data will be evaluated and collected from the medical records of all patients with Chronic Inflammatory Bowel Diseases followed at the SSD Chronic Inflammatory Bowel Diseases center. For patients with a diagnosis of kidney disease still affiliated with the center, prospective data collection will occur for a period of 3 years from enrollment in the study. No additional study-specific analyses or procedures are planned.

• Sample Size Approximately 1500 patients with Chronic Inflammatory Bowel Diseases are expected to be enrolled.
• Statistical Analysis All analyses will be performed using Stata 13.0 for Windows. The characteristics of the enrolled and observed patients will be summarized using descriptive statistics. All variables will be summarized with descriptive statistical analyses. For qualitative variables: relative frequency and 95% confidence intervals; for quantitative variables: mean, standard deviation, and percentiles. To detect possible associations between observed qualitative characteristics, Pearson's Chi-square test will be used, along with Yates' continuity correction or Fisher's exact test. Analysis of variance (ANOVA) or analysis of covariance (ANCOVA) will be used for quantitative variables.

Statistical analysis will be conducted using the Stats package. Differences between groups will be evaluated with Student's t-test and uni- and multivariate analyses to identify risk factors.

Inclusion Criteria:

• Signed informed consent
• Age ≥ 18 years
• Diagnosis of Crohn's Disease or Ulcerative Colitis

Exclusion Criteria:

• None

Patients with Chronic Inflammatory Bowel Diseases who have been followed at the SSD Chronic Inflammatory Bowel Diseases center. For patients with a diagnosis of kidney disease still affiliated with the center, data collection will be conducted prospectively for a period of 3 years from enrollment in the study.