Several factors influence the success of surveillance. Firstly, the ability to detect dysplasia may be variable. Random biopsy sampling was based on the presumption that dysplasia is frequently not associated with visible mucosal abnormalities. To detect dysplasia with 90 % probability, 33 serial colonic biopsies from four quadrant biopsy specimens need to be obtained every 10 cm from each anatomical segment of the colon [67]. This practice has been endorsed by multiple societies [2–4]. Although possibly true at the inception of surveillance, evolution in endoscopic technology over the years, through standard definition colonoscopy using video chips to high-definition colonoscopy and indeed evidence that most dysplasia is visible at standard white light colonoscopy has challenged this view [17, 68]. Furthermore, random biopsies sample well less than 1 % of total colonic mucosa and one study suggested that up to 1266 random biopsies would be needed to detect one additional episode of dysplasia [69, 70]. In a study in which UC patients underwent colonoscopy every 2 years, interval cancers were observed to develop between 10 and 28 months after dysplasia-free examination [71]. Dysplasia can still be present in a normal appearing colon [17]. Additional aspects such as resectability of dysplasia, anatomical features such as pseudopolyps and a shortened tubular colon may pose difficulties with dysplasia detection. Colonic inflammation can also make pathologic discrimination of dysplasia difficult, thus surveillance should ideally take place when the patient is in clinical remission. All this should be discussed carefully with patients when committing to a surveillance program. Despite this, evidence suggests that patients do not wish to consider colectomy until there is a relatively high certainty of cancer underpinning the importance of careful considerations and meticulous assessment using the best available technology and skill to detect and reset dysplasia to avoid IBD-CRN and colectomy [72].

Meanwhile, new imaging techniques such as chromoendoscopy , narrow band imaging, and confocal endomicroscopy have been developed as an adjunctive technique to detect more subtle mucosal abnormalities. Multiple studies have demonstrated a superior diagnostic yield and therapeutic advantage with chromoendoscopy when compared with standard random biopsy and white light technique for index screening of dysplasia in colitis [73–78]. Meta-analysis of these trials supports the use of chromoendoscopy with targeted biopsies for detecting dysplasia being 8.9 times more likely to detect any dysplasia and 5.2 times more likely to detect non-polypoid dysplasia than white light endoscopy with random biopsy [79, 80]. Such evolution in knowledge has seen cautious translation in societal recommendations over the years. Thus, the ACG 2010 guidelines considered it premature to endorse chromoendoscopy in low-risk patients [4]. The CCFA 2004 and AGA 2010 guidelines, however consider chromoendoscopy with targeted biopsies as a reasonable alternative to white light endoscopy for endoscopists experienced in this technique [2, 3]. All recent European guidelines (ECCO, BSG, NICE) and recent ASGE guidance endorse chromoendoscopy with targeted biopsies as a surveillance protocol of choice [5–8]. The recently published SCENIC international consensus statements recommend chromoendoscopy over standard white light colonoscopy and suggest chromoendoscopy over high-definition colonoscopy for dysplasia surveillance in IBD [68]. Meta-analysis showed a significantly greater proportion of dysplasia detection at chromoendoscopy (RR 1.8, absolute risk increase 6 %) then white light colonoscopy alone [68]. This strategy has also been shown to be cost-effective especially with increasing surveillance interval based on the risk of CRC [81]. Although the SCENIC consensus recommends chromoendoscopy over high-definition white light colonoscopy it was acknowledged that this recommendation is conditional being based on a small observational study [68, 82]. Where chromoendoscopy expertise is not available SCENIC recommends high-definition over standard white light colonoscopy [68]. Chromoendoscopy involves the use of topical contrast agents, either 0.1 % methylene blue or 0.03–0.5 % indigo carmine. Excellent bowel preparation is a prerequisite. Colonic mucosa is segmentally sprayed with contrast agent after cecal intubation and upon withdrawal, using a spray catheter or through the forward water–jet channel using an automated pump [73–75, 80, 81, 83]. Chromoendoscopy enhances mucosal irregularities and helps to delineate the lesion morphology, size, and border to evaluate for endoscopic features of submucosal invasion. Thus, endoscopically resectable lesions may be resected if feasible or tattooed and referred to an endoscopist with expertise in endoscopic mucosal resection or dissection as appropriate. Targeted biopsies should be taken from lesions deemed unresectable endoscopically and lesions of uncertain significance. Furthermore, at least two histological staging biopsies from each colonic segment are recommended to determine histological extent and severity of disease, which in turn affects the risk of dysplasia [5, 6, 8, 9]. Random biopsies however, are not recommended if chromoendoscopy is used for dysplasia surveillance [1, 5, 6, 8, 48]. Successful delivery of dysplasia surveillance using chromoendoscopy hinges on several factors. These include appropriate training (endoscopist and nurses), lesion recognition and its associated learning curve, inter-observer variability amongst pathologists in identifying and grading dysplasia and indeed operational barriers such as availability of dye and equipment, procedural time resulting in some hesitancy amongst gastroenterologists in adopting this modality and in some instances referral to “experts” to provide this [68]. Furthermore, heightened sensitivity of chromoendoscopy in detecting dysplastic foci notwithstanding, the natural history of additional, smaller, flatter lesions identified at chromoendoscopy is poorly understood [84]. The rate of progression from indefinite and low-grade dysplasia to cancer appears to be low some in high-risk cohorts even when variables such as primary sclerosing cholangitis and previous advanced dysplasia are factored in [30–33]. To add to this conundrum, data from the Surveillance, Epidemiology and End results Medicare-linked database of patients over 67 years showed that interval cancers 6–36 months after colonoscopy occurred in much higher proportion of patients with IBD (15.1 % with Crohn’s disease and 15.8 % with ulcerative colitis) than patients without IBD (5.8 %) suggesting that clinically relevant areas of neoplasia may be missed with current colonoscopy surveillance [85]. However, the futility of random biopsy has been demonstrated repeatedly in prospective studies. Meanwhile, the evolution in our knowledge of the natural history of dysplasia and the clinical implications of dysplasia found by chromoendoscopy through its wider adoption may close many gaps in our understanding of its true utility. The bulk of evidence favors chromoendoscopy for surveillance and is backed by several scientific societies and international consensus opinion [5, 6, 8, 9, 68]. Several organizations elected not to endorse the SCENIC recommendations feeling that additional studies are needed to confirm that clinical outcomes are improved with chromoendoscopy. A summary of recommendations from the SCENIC consensus for surveillance and management of dysplasia in patients with IBD is outlined in Table 60.3.

Other techniques for image-enhanced endoscopy are under investigation. Narrow-band imaging (NBI), an optical chromoendoscopy technology that uses filters to enhance the contrast of the mucosa and vasculature has not demonstrated an increased yield for dysplasia detection in randomized studies comparing NBI to either standard definition white light endoscopy (WLE) or high definition WLE [86–89]. Studies comparing NBI with chromoendoscopy have reported a numerically higher detection rate with chromoendoscopy but at meta-analysis the difference was not statistically significant. The SCENIC consensus, therefore, does not recommend NBI over dye spray chromoendoscopy [68]. Autofluorescence and confocal laser endomicroscopy are under study but current data do not support their routine use [5, 68].