Coletta and colleagues also highlighted the role of AA in a recent meta-analysis where the pooled sensitivity and specificity was 92% and 96% for the diagnosis of high-grade dysplasia and oesophageal adenocarcinoma ( 18). This increases the yield of detecting dysplastic lesions and facilitates targeted biopsies. In addition, using AA had a sensitivity and specificity of 98% and 84% respectively ( 17). Not surprisingly, high-grade dysplastic lesions and intramucosal cancer took between 23–53 seconds to lose the aceto-whitening effect compared to non-dysplastic lesions which continued to hold on to this effect for up to a median duration of 311 seconds (P<0.05). The duration of the aceto-whitening effect was further studied by Longcroft-Wheaton and colleagues who objectively measured and compared the effect of AA on dysplastic and non-dysplastic lesions. With neoplastic lesions which lack cellular proteins, the aceto-whitening reaction is not visible or is lost quickly compared to normal non-dysplastic BO epithelium. When sprayed onto the Barrett’s mucosa, a reversible acetylation of cellular proteins occurs leading to a so-called “aceto-whitening reaction” ( Figure 1) ( 16). The principle is not dissimilar to AA employment in the field of gynaecology to screen for dysplastic uterine cervical lesions which was well established in the early 1990s ( 15). This novel use of AA chromoendoscopy in BO was introduced in 2001 by Guelrud and colleagues ( 14). Nevertheless, chromoendoscopy still plays a major role in several conditions.ĪA chromoendoscopy in Barrett’s neoplasia Virtual chromoendoscopy is technically less cumbersome, easier to apply and saves time ( 9, 10). Over the years, the introduction and adoption of ´virtual´ or electronic chromoendoscopy has rendered dye-based chromoendoscopy less relevant in day-to-day clinical practise. It also plays a key role in gastric metaplasia and adenocarcinoma, as well as in the colon particularly in patients with chronic colitis ( 6- 8). The use of chromoendoscopy has demonstrated good diagnostic yield in the evaluation of dysplastic lesions in Barrett’s oesophagus (BO) and oesophageal adenocarcinoma by facilitating targeted biopsies of suspicious areas ( 3- 5). In colonoscopy, good bowel preparation is critical the use of spasmolytic agents such as scopolamine or glucagon can be used to avoid bowel peristalsis and an uneven distribution of the dye in some cases. In addition, a foot pump can be useful in some cases, such as for pancolonic dye spraying in patients with inflammatory bowel disease (IBD). Special caution should be exercised whilst staining the upper oesophagus, due to the risk of aspiration. In a stepwise manner, segments of approximately 20 cm should be stained each time and then carefully inspected. The endoscope should be slowly withdrawn, while the endoscope tip (with a 1–2 cm protruding spraying catheter) is directed in spiral movements onto the mucosa and simultaneously, the dye is sprayed continuously. The amount of staining solution required depends on the surface area to be stained. Spraying catheters allow the most controlled and precise application of the dye as a fine mist onto the GIT surface. Chromoendoscopy can complement imaging through enhancing features of mucosal surface topography and may assist in providing in-depth details that enables subsequent therapeutic decisions to be made with greater precision ( 2). The technique encourages endoscopists to study a particular area of interest with greater clarity and sharpness. This is generally achieved by using a variety of dyes to distinguish normal from abnormal mucosa ( 1). Chromoendoscopy aids the endoscopist in highlighting and characterising lesions in the gastrointestinal tract (GIT).
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