Crohn's disease (CD) is a nonspecific chronic inflammatory condition characterized by a protracted course with alternating periods of relapse and remission. Even patients who achieve deep remission remain prone to recurrence and require long-term follow-up. While various monitoring methods are available, endoscopy plays a primary role in the management and diagnosis of CD; however, its relative invasiveness and the need for bowel preparation limit the feasibility of continuous monitoring. In contrast, transabdominal intestinal ultrasound offers advantages such as non-invasiveness, absence of radiation, good patient tolerance, and low cost, making it suitable for long-term monitoring. However, most studies have focused on exploring its concordance with disease activity and endoscopic findings, with only a limited number of studies examining its clinical significance for long-term prognosis.

Therefore, we conducted a multicenter prospective study involving 18 months of follow-up in CD patients who achieved deep remission. Based on the follow-up results, patients were divided into relapse and non-relapse groups. Stratified analysis was performed according to the Montreal classification to compare color Doppler ultrasound parameters between the two groups and within each stratum, and to establish a predictive model.

Inclusion Criteria:

• Patients previously diagnosed with Crohn's disease via endoscopy and histopathology at other hospitals or at our institution; patients aged 18-70 years; Complete clinical data and biochemical parameters are available for the week before and after endoscopy, including comprehensive patient demographics and laboratory indicators such as complete blood count, liver function, kidney function, CRP, and ESR; a color Doppler ultrasound of the intestines was performed at our hospital within one week before or after endoscopy, and the relevant records are complete; patients assessed to have achieved deep remission based on endoscopic and other data.

Exclusion Criteria:

• Patients with concomitant colorectal cancer; patients with severe cardiovascular, respiratory, or urinary dysfunction; pregnant or lactating women; patients younger than 16 or older than 70 years of age; patients who changed their maintenance therapy regimen upon achieving deep remission; patients with incomplete medical records, such as color Doppler ultrasound of the intestines.

Patients with CD who have achieved clinical remission as assessed by evaluation and mucosal healing as assessed by endoscopy