Evaluation and Detection of Dysplasia in IBD: the Role of Chromoendoscopy and Enhanced Imaging Techniques

Patients with ulcerative colitis (UC) and Crohn's disease (CD) colitis are at significantly higher risk for the development of colitis-associated colorectal cancer (CAC), a risk associated with increased duration and extent of disease [1]. CAC in patients with ulcerative colitis and Crohn's colitis arises from dysplastic tissue in the background of mucosal inflammatory changes. Regular surveillance by colonoscopy is a recommended cancer prevention strategy endorsed by the US and European GI societies [2-4]. Until recently, random sampling of the mucosa throughout the colon has been the mainstay of this conventional surveillance. This requires multiple biopsies to be taken and processed, a practice which is time consuming, expensive, and has a low diagnostic yield. The growth pattern of dysplastic tissue is often multifocal and diffuse, and thus, its detection may not be optimal with the use of traditional white light colonoscopy. According to recent studies, most dysplastic lesions appear to be visible to careful endoscopic inspection [5-7]. Thus, the approach focusing on targeted biopsies of any mucosal abnormalities instead of only random biopsies has been advocated [8]. In addition, the detection and further delineation of any mucosal abnormalities are thought to be improved by the application of dyes that highlight more subtle abnormalities known as chromoendoscopy (CE) as well as a new generation endoscopic system with high-definition white light endoscopy (HDWL). The application of CE in patients with long-term UC was deemed to be beneficial based upon the results of previous clinical trials comparing CE with standard definition white light endoscopy (SDWL) [9•, 10•]. However, there are limited data available comparing CE with the currently broadly used high-definition colonoscopies (HDWL) [11•, 12•, 13•]. High-definition (HD) endoscopy uses a high-definition monitor and a high-resolution CCD (charge-coupled device) providing images of substantially higher resolution than standard video endoscopy. Thus, HDWL colonoscopy may be an alternative to CE in IBD surveillance without the need for the extra time and required experience with CE. Further longitudinal studies are necessary to determine the ultimate advantage of chromoendoscopy or lack of the advantages of chromoendoscopy over that of high-definition colonoscopy in detection of dysplasia. Once lesions are identified by HDWL and CE, they can be further evaluated with evolving technologies to perform in vivo microscopy. Small-field technologies such as confocal endomicroscopy (CLE) permit in vivo microscopic assessment of the colonic mucosa. This evolving technology can be utilized in combination with HDWL and CE in selected cases to further define the lesions and assess their histology, and thus, facilitate real-time in vivo diagnosis and decisions regarding resection of lesions. Further studies to determine the applicability of these newer enhanced technologies in evaluation of dysplasia in routine clinical practice are needed.