Objective:To prospectively follow up the patients with ileocecal inflammatory lesions, to explore the characteristics of Crohn′s disease(CD) at early stage, and to provide references for early diagnosis of CD.Methods:From January 2013 to December 2018, at Department of Gastroenterology, The Seventh Medical Center of PLA General Hospital, 232 patients with unexplained ileocecal inflammatory lesions under colonoscopy examination were enrolled, which were followed up for more than one year. Chi-square test and Fisher exact probability text were used to compare the patients with early CD, with non-specific enteritis and intestinal tuberculosis in abdominal symptoms (abdominal pain, diarrhea, abdominal distension, constipation, hematochezia, changes in bowel habits), accompanying symptoms (oral ulcer, arthralgia), the proportion of patients with elevated erythrocyte sedimentation rate (ESR) or elevated C-reactive protein (CRP) level, serum antineutrophilic cytoplasmic antibody (ANCA), anti-saccharomyces cerevisiae antibody (ASCA), tuberculosis infection of T cells spot test, positive rate of fecal occult blood, lesion size, morphology, involvement site under endoscopy and histopathological results. Multivariate binary logistic regression was used to analyze the related factors of early CD.Results:Among 232 patients, 155 were males and 77 were females, and the age of first diagnosis was (43.9±13.8) years old. The follow-up period (range) was 27 months (12 to 79 months). Twenty-nine cases (12.5%) were diagnosed as early CD, 45 cases (19.4%) were intestinal tuberculosis, 105 cases (45.3%) were non-specific enteritis, and 53 cases (22.8%) as undetermined. All of 29 patients with early CD had abdominal symptoms, which accounted for 16.9% (29/172) of 172 patients with ileoceccal inflammatory lesion as well as abdominal symptoms. In early CD patients, the proportions of patients with abdominal pain, elevated CRP level and ESR level, positive rate of ASCA, positive rate of tuberculosis infection T cells and percentage of patients with thickened intestinal wall were all higher than those in patients with non-specific enteritis (62.1%, 18/29 vs. 33.3%, 35/105; 13.8%, 4/29 vs. 0; 13.8%, 4/29 vs. 1.0%, 1/105; 24.1%, 7/29 vs. 1.0%, 1/105; 20.7%, 6/29 vs. 3.8%, 4/105; 95.7%, 22/23 vs. 0), and the proportion of patients without abdominal symptoms was lower than that of patients with non-specific enteritis (0 vs. 31.4%, 33/105). And the differences were statistically significant ( χ2=6.692, Fisher exact probability text, χ2=7.162, χ2=17.826, χ2=7.497, Fisher exact probability text, and Fisher exact probability text, all P<0.05). Early CD patients were more likely to have multiple lesion sites (55.2%, 16/29), and mainly deep ulcers (55.2%, 16/29) and ulcers with a long diameter of 5 to 10 mm (39.3%, 11/28). The lesions of non-specific enteritis were mostly confined to the end of ileum (75.2%, 79/105), which were mainly superficial ulcers (41.0%, 43/105) and ulcers with a long diameter less than 5 mm (69.0%, 49/71). The proportion of patients without abdominal symptoms and the positive rate of tuberculosis infection of T cells spot test of early CD patients were both lower than those of intestinal tuberculosis group (0 vs. 15.6%, 7/45 and 20.7%, 6/29 vs. 68.9%, 31/45). The positive rate of ASCA and the proportion of patients with thickened intestinal wall were higher than those of intestinal tuberculosis group (24.1%, 7/29 vs. 0 and 95.7%, 22/23 vs. 11/19), and the differences were statistically significant (Fisher exact probability text, χ2=13.713, Fisher exact probability text and χ2=6.710, all P<0.05). The results of multivariate binary logistic regression analysis showed that abdominal pain and positive ASCA were independent risk factors for early CD (odds ratio ( OR)=2.855, 95% confidence interval ( CI) 1.014 to 8.037, P=0.047; OR=10.033, 95% CI 2.274 to 44.250, P=0.002). Conclusions:Prospective follow-up for more than one year in patients with unexplained ileocecal inflammatory lesions can effectively identify and diagnose early CD. Ileocecal inflammatory lesions with abdominal symptoms are one of the early manifestations of CD. Abdominal pain and positive serum ASCA at the initial diagnosis are independent risk factors for early diagnosis of CD.