After exclusion of ITB, the initial diagnosis of IBD remains challenging because many other diseases have similar clinical and endoscopic presentations. Unlike Western countries where intestinal infectious diseases are uncommon, these entities remain strong competing diagnoses against IBD in China. Approximately 38% of patients with mucoid bloody diarrhea and suspected IBD turned out to have an infectious etiology [15]. Endoscopy is the most sensitive method for evaluating mucosal abnormalities, and is the only method to obtain biopsy for histologic and microbiological studies. The following are some infectious colitides relatively common in China that should be excluded before making a diagnosis of IBD.

Amebic colitis (Entamoeba histolytica) is a protozoan infection that most commonly affects the cecum and right colon. Colonoscopy typically reveals friable and erythematous mucosa with discrete large ulcers covered by mucopurulent exudates (Fig. 25.2). Biopsy specimens of the ulcer margins provide a sensitivity of 60–90% for trophozoites to make the diagnosis [16].

Schistosomiasis (Schistosoma japonicum) is predominantly endemic in the lake and marshland areas in central and east China. The parasite infects 5.1% of regional people, and causes significant morbidity [17]. Endoscopic features include free pus, intense mucosal reddening, and yellowish exudates in the mucosal surface (Fig. 25.3). In some cases, schistosomiasis presents skipping lesions that mimic CD.

Patients who present with IBD are prone to opportunistic infections including cytomegalovirus (CMV) and Clostridium difficile (C. difficile). In a cohort of IBD patients from central China, the prevalence, risk factors, and clinical presentation of CMV infection are comparable to those in Western IBD patients [18]. The characteristic colonoscopic finding of C. difficile colitis is pseudomembrane formation comprising yellow-white plaques. But in IBD patients superinfected by C. difficile, endoscopy findings may be relatively unspecific [19] (Fig. 25.4). Fecal assay of C. difficile toxin A and B confirms the diagnosis.

Similarly to Japan and Korea, noninfectious diseases such as intestinal Behçet’s disease (BD), ischemic colitis, and radiation colitis are also common in the Chinese population. These disorders should be taken into consideration before making a diagnosis of IBD. Among these entities BD resembles CD in many aspects, and often creates a diagnostic dilemma. Both diseases commonly have a young age of onset, nonspecific gastrointestinal symptoms, similar extraintestinal manifestations, and chronic, waxing and waning course. A comparative study conducted in our institute revealed some valuable strategies for the distinction of BD and CD. In terms of colonoscopic findings, the study showed that focal involvement, ileocecal valve deformity, solitary ulcers, large ulcers (>2 cm), and circumferential ulcers were more common in intestinal BD patients, whereas segmental involvement, longitudinal ulcers, a cobblestone appearance, and pseudopolyps were more common in CD (Figs. 25.5 and 25.6) [20].

Patients with long-standing UC and CD are associated with an increased risk of developing precancerous dysplasia lesions and colorectal cancer. Chinese IBD consensus endorsed a screening and surveillance strategy based on risk stratification [15]. The majority of colonic dysplastic lesions are macroscopically detectable, although the endoscopic appearance can be subtle, varied, and mimics post-inflammatory alterations. To date, chromoendoscopy is the only technique that has consistently yielded positive results in large, well-designed clinical studies [21]. Chinese IBD consensus recommends chromoendoscopy as a preferred dysplasia- detection tool [14]. Narrow-band imaging (Fig. 25.7), I-SCAN (Fig. 25.8), Fuji intelligent chromoendoscopy (FICE), and confocal laser endomicroscopy have yielded conflicting results, but have potential value to detect and diagnose dysplasia in selected patients.