Overview of evidence (non-systematic literature review)
No systematic reviews were undertaken for this topic. Practice points were based on selected evidence and guidelines (see Guideline development process).
Inspection on withdrawal could contribute to polyps being missed, as visualisation of the proximal surface of haustral folds may be limited. Several back-to-back colonoscopy trials have reported adenoma miss rates of up to 25%. Sessile serrated adenomas or non-polypoid lesions have limited contrast in relation to the surrounding mucosa and can be overlooked. This may contribute to the relatively high risk of interval cancers in the proximal colon. As a result, 'add-on' technologies have been developed to improve visualisation, especially in areas behind haustral folds. These include:
- Transparent Cap (TC)
- G-EYE endoscope
- Third Eye Panoramic device
- Third Eye Retroscope.
The TC is the most studied add-on device. The cap is attached to the tip of a colonoscope prior to the examination. Although adding to the cost of colonoscopy, it has been proposed as a method for shortening withdrawal time in addition to improving adenoma detection rates (ADR). When used by more experienced colonoscopists, the TC does not improve either the caecal intubation rate or the ADR, but does shorten the caecal intubation time. It may have utility for difficult cases, especially when initial caecal intubation fails. A meta-analysis of 16 studies examining the role of the TC revealed a marginal benefit for polyp detection rate (relative risk 1.08) and no difference in ADR. However, the TC has been shown to improve detection of serrated lesions (12.8% vs 6.6%).
Brand et al recently published the results of a pooled analysis of three technologies (the Third Eye Retroscope, the Full Spectrum Endoscope, and the EndoRing), concluding that these adjunct technologies may enhance detection of small (<10mm) adenomas.
In a multicentre back-to-back study involving 116 patients comparing colonoscopy with and without the EndoRing reported, adenoma miss rates of 10% versus 48% and polyp miss rates of 9% versus 53%.
The Endocuff is a similar device, which appears to increase the detection of diminutive polyps and improve ADR. However, a larger randomised control trial involving 1063 patients showed no change in the ADR.
Shirin et al recently conducted a study over >1000 patients using a balloon based device, the G‐EYE colonoscope. Significantly more adenomas were detected when this technology was used compared with conventional colonoscopy.
With all of these devices the additional cost is a factor that must be considered before incorporation into practice, considering the modest gains reported.
Chromoendoscopy (dye spray) has been introduced to enhance the detection of polyps, particularly diminutive flat lesions that may be otherwise difficult to detect. When combined with high magnification, chromoendoscopy was found to be highly efficient in differentiating adenomatous from non-adenomatous polyps. It has also been strongly advocated in patients undergoing surveillance for IBDinflammatory bowel disease (IBD). However, in a more recent non inferiority trial, high-definition white-light endoscopy was as effective as chromoendoscopy (see also Colonoscopic surveillance and management of dysplasia in inflammatory bowel disease (IBD)).
Based on results from their studies, Lapalus and Le Rhun could not recommend the systematic use of chromoendoscopy for overall adenoma detection, although there was improvement seen in detecting small adenomas in the proximal colon. Other studies reported that chromoendoscopy detected more polyps compared with standard colonoscopy, particularly in patients with Lynch syndrome.
Despite being advocated for close to two decades, chromoendoscopy struggles to be accepted in mainstream clinical practice and as a result appears to have been superseded by electronic image enhanced technologies for characterisation of colorectal polyps.
Carbon dioxide (CO2) insufflation
A recent meta-analysis has confirmed that, when compared to air insufflation, CO2 insufflation clearly reduces post-colonoscopy pain and distension and allows more rapid caecal intubation, but does not improve completion rates or adenoma detection. It appears to be safe even in patients with airway disease.
Barriers to implementation include the lack of incorporation of CO2 insufflation into standard endoscopy systems, the resulting cost of retrofitting CO2 insufflation, and the ongoing cost of the gas itself, estimated at US$3 per procedure.
Chromoendoscopy should be considered for routine colonoscopy to improve the detection and characterisation of colorectal polyps.
Chromoendoscopy should be considered for patients undergoing surveillance for inflammatory bowel disease, although a recent study has shown equivalence with high resolution white-light endoscopy.
CO2 insufflation should be used routinely to improve patient tolerability of colonoscopy.
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