Narrow Band Colonoscopy

Mixed Results on Narrow-Band Imaging

A standard colonoscope uses a regular white light to illuminate the colon. Narrow-band imaging uses an optical filter to produce blue light, which provides more contrast between the polyp and the colon lining. At the push of a button, a colonoscope with narrow-band imaging capabilities can switch between white light and blue light. Blue light has a narrower wavelength, which is why the device is called "narrow-band" imaging.

Researchers hypothesized that narrow-band imaging would improve a doctor's ability to find polyps. But clinical trials have shown mixed results, with one randomized study reporting improved polyp detection and three others showing it was no better than standard white-light colonoscopy. Based on these results, narrow-band imaging will likely not be used to improve detection of polyps.

Where narrow-band imaging appears most promising, however, is in differentiating benign polyps from those that are cancerous or precancerous. Today, the standard of practice is to remove all polyps and send them to the pathology lab for analysis. But about a third of these polyps end up being benign and thus were removed unnecessarily, putting the patient at risk -- albeit a small risk -- for bleeding complications.

Narrow-band imaging can visualize differences in surface and blood vessel patterns that can help determine whether or not a polyp is cancerous. So far, six well-designed studies have investigated whether narrow-band imaging can be used accurately to differentiate polyp types during colonoscopy. These studies found that using narrow-band imaging, doctors could accurately identify suspicious and benign polyps about 80 to 90% of the time.

Although a narrow-band imaging colonoscope called Exera is commercially available, more research and refinement of this technology are necessary to bring the accuracy rate closer to 100%. If this level of accuracy is reached, doctors could begin diagnosing polyps during colonoscopy, removing only those that are life-threatening and leaving benign ones in place.