Crohn's disease (CD) is a chronic granulomatous inflammatory bowel disease (IBD) with unknown etiology. Although CD can involve the whole digestive tract, it more commonly involves only the terminal ileum. Intestinal inflammation develops gradually over time, eventually leading to severe intestinal dysfunction or even loss of intestinal function[1]. In recent years, the incidence of IBD in Asia, especially in East Asia, has significantly increased, possibly because of the gradual westernization of lifestyle and industrialization[2], [3], [4].he assessment of disease activity with stratification for CD patients is crucial for the determination of a therapeutic strategy and prognosis. Therefore, an efficient method is needed to comprehensively assess CD.

Various indices are used to evaluate CD activity, including the CDAI. However, the reliability of CDAI has been questioned due to its subjectivity and complexity. It has been reported that in a randomized controlled study, the response rate of the CDAI score to placebo was as high as 33%[5], [6]. Studies have also shown that inflammation biomarkers, such as C-reactive protein (CRP), erythrocyte sedimentation rate (ESR), and fecal calprotectin, are significantly correlated with endoscopic activity and the risk of CD recurrence. For example, if the CRP level continues to increase during treatment, the prognosis is likely to be poor[7], [8]. It is well known that the risk of arteriovenous thrombosis in IBD patients is three times higher than that in normal subjects, which may be related to the increase of platelets and coagulation-related active substances (e.g., D-dimer and fibrinogen) in patients with active CD[9], [10]. At present, endoscopic remission has often been used as the gold standard for evaluating the degree of inflammation in the intestinal mucosa. However, some studies have not observed a significant correlation between endoscopic mucosal lesions and clinical activity in CD. It is believed that CD, as a disease involving the whole intestinal wall, should be assessed by typical transmural inflammatory changes rather than superficial mucosal lesions[11]. Furthermore, since CD often affects the small bowel beyond the terminal ileum, ileo-colonoscopy alone may still be inadequate for the correct evaluation of mucosal inflammation in CD.

In recent years, CTE has been used as a non-invasive imaging technique to evaluate CD activity or postoperative recurrence. CTE can accurately reflect the distribution of lesions and inflammatory changes in the entire intestinal wall in an easy and semi-quantitative manner. At the same time, CTE has the advantages of simplicity and good patient tolerance[12], [13]. Moreover, it is better able to dilate and observe the small intestine, especially the proximal small intestine, allowing an improved detection and diagnosis of high-order CD lesions as compared with enteroscopy. By 2008, CTE had surpassed endoscopy as the preferred examination method for CD[14]. The CTE signs have been well described and are closely associated with CD activity, which include mural stratification, mural hyperenhancement, bowel wall thickening, haziness of the surrounding mesenteric fat, and the comb sign. Moreover, magnetic resonance enterography (MRE) has a similar sensitivity to CTE with mucosal lesions, while having the advantage of the absence of any radiation exposure. However, not all centers can readily perform MRE anytime. On the other hand, CTE is cheaper, more readily accessible, and better tolerated by patients. The decision for which cross-sectional imaging to use is in part related to the expertise of the institution and the clinical presentation of the patient[15], [16], [17].

Despite their widespread application in clinical practice, the relative performances and relationships between CTE, biochemical indicators, and endoscopy as diagnostic tools to evaluate the therapeutic response in CD have yet to be determined. The aim of this study is to determine the correlation between endoscopic disease activity, biochemical markers, and the CTE findings of inflammatory activity in CD patients, allowing a more accurate evaluation of CD activity and providing new directions for the treatment of CD.