OAK BROOK, Ill.―According to a new study, the use of narrow band imaging (NBI) during colonoscopy is sufficiently accurate to allow distal hyperplastic (non-cancerous) polyps to be left in place without removal and small, distal adenomas (pre-cancerous polyps) to be removed and discarded without pathologic assessment.
These findings validate NBI criteria based on color, vessels and pit characteristics for predicting real-time colorectal polyp histology. The study appears in the August issue of GIE: Gastrointestinal Endoscopy, the monthly peer-reviewed scientific journal of the American Society for Gastrointestinal Endoscopy (ASGE).
There are two common types of polyps in the colon: hyperplastic polyps and adenomas. Colorectal cancer may develop from colon adenomas. A hyperplastic polyp does not increase cancer risk. Adenomas, however, are thought to be the precursor (origin) for the majority of colorectal cancers, although most adenomas never become cancerous. Colonoscopy can find polyps, which can then be removed (polypectomy), before they turn into cancer. The distal colon, or rectosigmoid, includes the regions of the lower colon that are closest to the anal opening and often contains hyperplastic polyps.
Narrow band imaging during colonoscopy offers the potential for improved visualization over conventional colonoscopy and was developed to enhance certain mucosal or vascular characteristics so that abnormal growths could be better visualized. It uses a special filter to illuminate tissue in the lining of the intestine with light at specific wavelengths, thereby enhancing underlying vasculature and producing the greatest contrast between blood vessels and the surrounding mucosa. This can help the endoscopist see the margins of an abnormal growth better and assist in determining which areas are best to biopsy or remove.
“New imaging technologies that allow in vivo, real-time assessment of polyp type could transform the clinical approach to management of diminutive colorectal polyps. Currently, diminutive colorectal polyps, less than or equal to 5 mm, are removed endoscopically and submitted for pathologic assessment. The pathologic assessment is used to guide post-polypectomy surveillance intervals. However, these polyps rarely harbor invasive cancer and seldom have high risk features such as villous elements or high-grade dysplasia," said study lead author Douglas K. Rex, MD, FASGE, Indiana University Hospital, Indianapolis. “We evaluated the feasibility of using NBI high-definition colonoscopes for leaving distal colon hyperplastic polyps in place during colonoscopy. We found very high levels of accuracy can be achieved for the endoscopic prediction of polyp type in the distal colon. Leaving distal colon hyperplastic polyps in place may be a relatively easy goal to achieve with acceptable accuracy by using narrow band imaging."