Since these guidelines were last updated in 2011, there has been ongoing research and development in endoscope design, aimed at improved detection of colonic neoplasia, reducing miss rates, and enhancing lesion characterisation for diagnosis. These new features include technologies aimed at increased mucosal views through wider angle visualisation and ultra-magnification endoscopic systems allowing in vivo histological assessment. Many of these technologies are now commercially available. However, there is still a need for further studies, including cost-benefit analysis, before they can be adopted as mainstream practice. Established technologies include high-definition colonoscopy, wide-angle colonoscopy and electronic chromoendoscopy, such as narrow band imaging (NBI; Olympus), flexible spectral imaging colour enhancement such as Fujinon intelligent chromoendoscopy (FICE) and i-SCAN (Pentax). These technologies are now incorporated into all of the latest generation colonoscopes, with high-definition white-light endoscopy (WLE) now the standard of care in routine colonoscopy.
Overview of evidence (non-systematic literature review)[edit source]
No systematic reviews were undertaken for this topic. Practice points were based on selected evidence and guidelines (see Guideline development process).
Extra-Wide-Angle-View colonoscopy[edit source]
Wide angle colonoscopy with vision of 170° has become standard in the latest generation colonoscopes. Despite the aim of improving the detection of lesions hidden behind colonic folds, all studies in the available literature, with one exception, suggest that wide angle colonoscopes do not significantly reduce polyp miss rates, which have been estimated to be has high as 31% in systematic reviews.
Given these high rates of missed lesions, there has been an emergence of new technologies aimed at reducing miss rates through wider mucosal visualisation up to 330°. These include Third Eye Retroscope and Third Eye Panoramic (Avantis Medical Systems). Fuse Full Spectrum Endoscopy colonoscopy platform (Endo-Choice Inc); and the Extra-Wide-Angle-View colonoscope (Olympus). While many of these technologies have shown promise through increased detection rates over standard forward viewing colonoscopy, none have shown an absolute superiority to standard colonoscopy and therefore cannot be recommended as standard of care. Continued emphasis has been placed on excellent bowel preparation, completed procedures to caecum and methodical, attentive and slow withdrawal as the keys to polyp detection.
Ultra-magnifying technologies[edit source]
In recent years there has been increasing interest in a 'predict-resect-and-discard' policy for management of diminutive polyps. Ultra-magnifying technologies such as confocal light endomicroscopy and endocytoscopy have advanced considerably and are now commercially available. These emerging technologies may offer most in correct histological classification of polyps prior to resection and discard or in surveillance in patients with inflammatory bowel disease (IBD). However, due to cost, time and the expertise required, they are still not part of mainstream practice (see also Recommended techniques for surveillance in IBD patients).
Electronic chromoendoscopy[edit source]
In the era of push-button technologies, electronic chromoendoscopy refers to imaging technologies that result in detailed contrast enhancement of blood vessels, which aids in lesion detection and characterisation. There is now a wide range of available technologies including NBI, FICE and i-scan.
Narrow-band imaging technology is the most commonly used and researched optical digital method of performing image-enhanced endoscopy. First-generation NBI had poor brightness and contrast enhancement, which limited its usefulness. The second-generation NBI, released in 2012, was able to deliver more than one-and-a-half times higher brightness, and twice the viewable distance in the lumen, than the first-generation NBI.
The utility of electronic chromoendoscopy over WLE has been evaluated in four broad areas:
- adenoma detection in individuals at average risk for colorectal cancer
- adenoma detection in hereditary syndromes
- dysplasia detection in IBD
- lesion characterisation.
With respect to adenoma detection in average risk individuals, most studies have compared NBI with WLE. Numerous studies, including multiple meta-analyses, have not demonstrated an advantage for NBI over WLE. Given these poor results, additional studies are required to determine the final application of these modalities in routine endoscopy practice.
In contrast to average-risk populations, in high-risk settings electronic chromoendoscopy has been demonstrated to result in improved detection rates over high-definition WLE.  The European Society for Gastroenterology currently endorses the routine use of high-definition panchromoendoscopy in patients with known or suspected Lynch syndrome or serrated polyposis syndrome – acknowledging, however, that overall evidence remains low.
Narrow-band imaging is the only modality studied in dysplasia detection in IBD and has not been demonstrated to improve detection rates over WLE (see also Recommended techniques for surveillance in IBD patients).
Lastly, lesion characterisation remains an area of promise for electronic chromoendoscopy technologies, with several studies showing high accuracy with negative predictive value >90%. However, these results have not been replicated outside of expert centres.
High-definition colonoscopes should be used routinely, as the mainstay of colonoscopy is a careful white-light examination of the well prepared colon.
Electronic chromoendoscopy should be used for lesion characterisation, but has limited value in lesion detection.
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