Troubleshooting where the sun don't shine

New technique scopes out adenomas better than traditional colonoscopy. Trust your Gut instincts

By Charles Rowe

Chromoscopy has shown promise in the effort to seek out potential trouble spots in the colon that would otherwise remain hidden. On top of that, the diagnostic efficacy of this technique increases when the whole colon is examined instead of just suspicious hot-spots, according to the results of a trial published in the March issue of Gut.

As men 50 years of age and older can cringingly attest, colonoscopy is a high stakes game of hide and seek most of them would rather not repeat. So collecting accurate results the first time around is imperative. A colonoscope can detect polyps but may miss small, flat lesions and adenomas that blend in and are harder to spot.

These troublesome lesions are easier to detect with a chromoscope, which uses a dye to improve resolution and a low-power lens at the business end of the probe. Typically, chromoscopy is done when a conventional colonoscopy has revealed suspicious sites. But how does a blanket examination of the colon with chromoscopy (pan-chromoscopy) compare with targeted chromoscopy?

The trial reported in Gut, headed by Dr D Paul Hurlstone of the Royal Hallamshire Hospital, Sheffield, UK, aimed to answer this question. Of the 260 consecutive patients examined by chromoscopy, 132 were randomly selected for the conventional targeted version (the control group). The remaining 128 patients received pan-chromoscopy.

Viewing the entire colon via pan-chromoscopy was significantly better for spotting trouble areas than looking at specific sites via the traditional targeted technique. Even more importantly, pan-chromoscopy was significantly better at revealing the presence of multiple adenomas (more than three) in patients. This crucial information could save lives since the presence of multiple adenomas is a high-risk red flag for the future development of colorectal cancer.

The trial had several built-in technical controls to minimize factors that could tamper with results. Extubation or the time taken to pull the scope out of the colon � the reverse journey is the best time to spot danger zones � was kept similar in both procedures. To further reduce variation between both procedures, the controls received a saline spray to mimic the use of indigo carmine dye in pan-chromoscopy.

"Colonic chromoscopy may improve our detection of [diminutive and flat] lesions," stated Dr Hurlstone. In routine practice, chromoscopy may allow a physician to determine who is at greater risk of colorectal cancer, the authors suggest.

However, this good news comes with a caveat. The interpretation of the images requires a lot of skill � a level of training and experience that is as yet uncommon. "Should the clinical evidence for chromoscopy... become apparent in long term followup studies, issues of additional training will need to be addressed," the investigators concluded.