This single-center retrospective cohort study aims to develop and internally validate a dynamic prediction model that uses longitudinal data from routinely collected blood tests to continuously assess the risk of Crohn's disease (CD)-related intestinal surgery, and to construct a simplified tool for clinical application. Patients with a confirmed diagnosis of CD and serial routine blood tests available during long-term follow-up will be included. Longitudinal trajectories of laboratory markers will be characterized, and their association with CD-related intestinal surgery will be evaluated. A full-variable dynamic prediction model will be built using dynamic random survival forest methodology, and a parsimonious model incorporating only the core laboratory markers will be developed via Bayesian joint model. The goal is to establish a practical, non-invasive, and dynamic risk assessment framework to support the transition from reactive to proactive long-term management of CD.

Inclusion Criteria:

• Confirmed diagnosis of CD
• Regular follow-up at this center for more than 5 years

Exclusion Criteria:

• Incomplete clinical data
• Fewer than 2 blood tests during the follow-up period

This retrospective cohort study included patients with a confirmed diagnosis of Crohn's disease (CD) at the Inflammatory Bowel Disease Center of the Sixth Affiliated Hospital of Sun Yat-sen University between January 1, 2010, and December 31, 2019. All patients had regular follow-up at this center for more than 5 years and had at least two routine blood tests available during follow-up. Data were retrospectively collected from electronic medical records, with the last follow-up date of December 31, 2026.

The individual participant data were collected retrospectively from routine clinical practice without specific informed consent for data sharing. Institutional ethics approval does not permit public deposition of patient-level data.