Detection of colorectal polyps behind the folds: a transparent hood or the Third Eye Retroscope?

We read with interest the article by Triadafilopoulos and Li [1] on the safety and efficacy of a new retrograde-viewing auxiliary imaging device, the Third Eye Retroscope, in improving colorectal diagnostic yield. The device was inserted through the instrument channel of a colonoscope and extended beyond the tip of the colonoscope, providing a continuous retrograde view and visualizing the proximal side of the folds, flexures, and ileocecal and rectal valves. When a polyp was detected, the device was temporarily removed from the instrument channel to allow insertion of a snare or forceps. Among 38 polyps detected, 4 polyps (11 %) behind folds were detected only with the retrograde-viewing device. We believe that a simple technique can detect polyps behind folds.

Because most colorectal cancers are believed to arise from adenomatous polyps, the detection and removal of polyps by colonoscopy has been recommended for the prevention of subsequent colorectal cancer [2]. However, some polyps and even cancers may be missed during colonoscopy because they lie outside the visual field, hidden either behind folds or at flexures [2] [3]. CT colonography simulation [4] has indicated that the percentage of colorectal surface visualized by conventional colonoscopy is only 86.6 %. Therefore, improved colonoscopic techniques that will carefully visualize the proximal side of folds and flexures are needed.

We and others have previously shown that the use of a transparent hood attached to the tip of a conventional colonoscope helps to examine the proximal side of folds and flexures by depressing folds and flexures, thus detecting more polyps [2] [3] [5] [6] [7] [8]. When a polyp behind a fold is invisible under conventional observation ([Fig. 1]), pressing the fold at the anal side of the polyp with the hood enables good visualization of the polyp ([Fig. 2]). Although the value of colonoscopy depends largely on the ability of the endoscopist [2], this technique requires less experience of endoscopists [2] [5] [7]. Moreover, total colonoscopy with the hood ensures a good visual field and easy recognition of luminal continuity at bends [2] [5] [7], thus resulting in high rates of cecal intubation and shortened cecal intubation times [5].

Fig. 1 The area behind the fold is invisible under conventional observation.

Fig. 2 When the fold is pressed up with the transparent hood, a polyp can be identified behind the fold.

As Triadafilopoulos and Li describe [1], when a polyp is detected, the insertion, removal, and reinsertion of the retrograde-viewing device lengthen the colonoscope withdrawal time and may hinder the efficiency of the device. The retrograde-viewing device is also special equipment, requires two endoscopy system units, and is not available in most institutions. The transparent hood is simple, inexpensive, and readily available in most institutions. We believe that this simple technique allows inspection of the blind areas behind the folds with a good visual field, and is an effective and more practical alternative for the detection of polyps behind folds.

Competing interests: None.

References

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