The Role of in Vivo Real Time Endocytoscopy in Diagnosing Colorectal Neoplasia

Colorectal cancer has been recognized as the second most common cause of cancer related death in the US (1). Most colorectal cancers arise from adenomatous polyps that progress. Colon polyps are usually classified as neoplastic (adenoma and carcinoma) and non-neoplastic (most commonly hyperplastic). Standard endoscopic inspection cannot reliably distinguish between polyp types. Thus, all visualized polyps during standard colonoscopies are typically removed. Since almost half of all polyps are hyperplastic, a large proportion of unnecessary polypectomies increase the time, risk, and cost of colonoscopies.

Various studies have showed improved diagnostic accuracy of different types of polyps when broad field techniques such as chromoendoscopy with the use of topical stains were used to detect and characterize lesions (2-4). Chromoendoscopy, though an approved method of lesion characterization during endoscopic evaluation of colorectal lesions, is time consuming and non-standardized. Recently small field techniques such as confocal microscopy and endocytoscopy have been introduced enabling visualization of the gastrointestinal tract at a cellular level, thus allowing diagnosis and classification of colorectal lesions in vivo.

Confocal endomicroscopy used along with chromoendoscopy to detect and characterize lesions has been studied extensively and reported to have a high accuracy in diagnosing neoplastic and nonneoplastic lesions of the gastrointestinal tract (5-12). One of the major limitations of the confocal system is the mandatory use of dyes such as topical Acriflavine or intravenous Fluorescein. However, there are issues with the application of these dyes; the risk of DNA damage with Acriflavine reduced its use. In addition, although intravenous fluorescein is FDA approved for diagnostic fluorescein angiography, its gastrointestinal application is an off-label indication and considered class IIb by the FDA. The other major limitation of the current confocal system is that it requires a dedicated confocal endoscope marketed by a single manufacturer. Thus, the use of confocal imaging requires purchase of specific confocal endoscopes.

Endocytoscopy is based on the technology of light-contact microscopy. The current endocytoscopy system (ECS) consists of two prototypes; Prototype one gives a low magnification (XEC300) with a maximal 450X magnification and field of view of 300X300 um, Prototype two provide a high magnification (XEC120) with a maximal 1100X magnification and a field of view of 120X120 um. In contrast to confocal endomicroscopy, the endocytoscopes can be easily passed through an accessory channel of the conventional therapeutic endoscope. This method does not require the use of intravenous contrast agents. Instead, it uses topical staining such as methylene blue or crestyl violet, which is applied routinely to facilitate visualization and removal of advanced colorectal polyps through endoscopic mucosal resection during colonoscopy.

The endocytoscopy system has only recently been introduced and hence there are very few studies reporting its use.