Version May 2024
INTRODUCTION — In Barrett's esophagus (BE), metaplastic columnar epithelium replaces the stratified squamous epithelium that normally lines the distal esophagus. The metaplastic epithelium is acquired as a consequence of chronic gastroesophageal reflux disease and predisposes to cancer development.
Endoscopic surveillance with random biopsies is routinely performed for patients with BE with the goal of detecting dysplasia before it progresses to adenocarcinoma. However, these dysplastic lesions are often small, focally distributed, and poorly visible with white light endoscopy. Routine white light endoscopic imaging provides limited detail of the mucosal surface, making it difficult to recognize early dysplastic changes. Advanced imaging technologies such as optical chromoscopy have been developed with the goal of providing detailed visualization of the mucosal and vascular patterns of BE, thus allowing for improved dysplasia detection.
Other advanced endoscopic imaging techniques continue to be studied to improve BE surveillance, and these are discussed separately:
●(See "Magnification endoscopy".)
●(See "Confocal laser endomicroscopy and endocytoscopy".)
●(See "Optical coherence tomography in the gastrointestinal tract", section on 'OCT of the esophagus'.)
●(See "Chromoendoscopy".)
This topic will summarize the experience with optical chromoscopy techniques in BE. The clinical manifestations, diagnosis, and management of BE are discussed separately. (See "Barrett's esophagus: Epidemiology, clinical manifestations, and diagnosis" and "Barrett's esophagus: Surveillance and management".)
PRINCIPLES — Optical chromoscopy is based upon the phenomenon that the depth of light penetration depends on its wavelength: the longer the wavelength, the deeper the penetration. Blue light penetrates only superficially, whereas red light penetrates into deeper layers. Optical chromoscopy uses narrowed bandwidths of blue (440 to 460 nm) and green (540 to 560 nm) light waves to improve the visibility of capillaries, veins, and other tissue structures by optimizing the absorbance and scattering characteristics of light [1]. Therefore, optical chromoscopy enables better visualization of the mucosal patterns because blue light allows for optimal imaging of the superficial (ie, mucosal) wall layers. Additionally, this technique reveals the superficial vasculature because hemoglobin absorbs the blue light. The filters for optical chromoscopy can be manually enabled (or disabled) during endoscopy, making it easy to switch between viewing with a standard white light mode or optical chromoscopy.
Optical chromoscopy techniques often involve the use of narrow band imaging (NBI) because it has been widely studied for the detection and characterization of early dysplasia during surveillance for BE [2]. NBI was the first available preprocessing technique, while blue light imaging (BLI) and optical enhancement (OE) were developed subsequently. Given the technical similarities, we will discuss these preprocessing techniques using the term optical chromoscopy.
In contrast, electronic chromoendoscopy uses postprocessing techniques and includes Fujifilm intelligent chromoendoscopy and i-scan [3]. However, preprocessing techniques have a better signal-to-noise ratio than postprocessing techniques, resulting in brighter images with a higher resolution.
Optical chromoscopy has several advantages when compared with dye-based chromoendoscopy:
●Staining agents are not required.
●It is operator friendly because the endoscopist can visualize the mucosa with optical chromoscopy by simply pressing a button on the endoscope.
●It allows for inspection of the entire mucosa within the endoscopic field of vision, whereas for dye-based chromoendoscopy, the staining agent often does not distribute equally over the mucosal surface.
In addition to these practical advantages, optical chromoscopy reveals the superficial vasculature of the mucosa with a higher degree of contrast, whereas the vascular pattern is often less visible in dye-based chromoendoscopy. (See "Chromoendoscopy".)
CLINICAL APPLICATIONS
Detecting dysplasia — High-definition white light endoscopy (HD-WLE) with random biopsies is the standard method for detecting intestinal metaplasia (IM) and dysplasia in patients undergoing surveillance for BE [4]. While routine HD-WLE can miss dysplastic lesions, most advanced imaging techniques do not significantly improve rates of early dysplasia detection. This may be related to the low prevalence of early dysplasia and to the detection of most dysplastic lesions using HD-WLE with random biopsies. However, future opportunities exist for using optical chromoscopy to provide detailed imaging of the mucosal and vascular patterns in patients with BE (picture 1 and picture 2).
To assess the value of new imaging technologies in BE, the American Society for Gastrointestinal Endoscopy has set benchmark values for BE surveillance (Preservation and Incorporation of Valuable Endoscopic Innovations [PIVI]). Novel diagnostic technologies for BE should meet selected performance thresholds for detecting dysplasia (ie, sensitivity ≥90 percent, negative predictive value [NPV] ≥98 percent, and specificity ≥80 percent) before implementing these techniques into routine clinical practice [5].
Data on surveillance of nondysplastic BE with narrow band imaging (NBI) have suggested that NBI meets these PIVI thresholds when performed by endoscopists with expertise in advanced imaging techniques [6-8]. In a trial including 123 patients with BE, NBI-targeted biopsies resulted in higher rates for detecting dysplastic lesions compared with HD-WLE with random biopsies (30 versus 21 percent), while NBI imaging required fewer biopsies (four versus eight biopsies) [8]. However, it should be noted that most studies were performed by expert endoscopists in tertiary referral centers where the baseline prevalence of BE dysplasia was higher than in a community-based population. In the community, the pretest likelihood of detecting dysplasia is lower, and endoscopists may have less experience with advanced endoscopic techniques. Additionally, most studies used a selection of still images, which do not always reflect mucosal visualization during real-time endoscopy. Other limitations of studies on optical chromoscopy for the detection of dysplasia in BE include a per-area/location/image design as opposed to a per-patient basis. In addition, pathology was frequently evaluated by a single experienced pathologist and not by consensus. Moreover, there was a longer duration of inspection with NBI and use of magnification with NBI. The possibility exists that a longer inspection time with HD-WLE alone would have resulted in increased BE dysplasia detection.
Given the limitations of these studies and the lack of estimated PIVI parameters for optical chromoscopy when performed in the general population, society guidelines have not recommended replacing HD-WLE examination and random biopsies with optical chromoscopy examination and targeted biopsies only [4,9].
Future studies will likely focus on the combination of improved targeted sampling with biopsies guided by a combination of HD-WLE, optical chromoscopy, and computer-assisted detection algorithms supplemented by wide-field sampling using brush cytology specimens. In particular, use of optical chromoscopy may facilitate targeted biopsies and may result in reducing the number of false-positive biopsies. A potential advantage of optical chromoscopy is the high NPV of a normal endoscopic appearance (ie, normal mucosal and vascular pattern), particularly in a patient population with BE and a low prevalence of dysplasia.
Assessing for areas of mucosal relief — Optical chromoscopy facilitates the assessment for subtle differences in mucosal relief (ie, subtle elevations and depressions relative to the normal-appearing flat surrounding mucosa) and may improve detection of early dysplasia in BE. In a cohort study including 68 patients with BE and single visible lesions (either high grade dysplasia or esophageal adenocarcinoma by histology), blue light imaging (BLI) provided better appreciation of surface relief and lesion description by the Paris classification compared with HD-WLE [10,11].
Inspecting a lesion prior to endoscopic resection — Optical chromoscopy may be used for inspecting and delineating early neoplastic lesions prior to endoscopic resection (ER), while data supporting this application are limited. (See "Barrett's esophagus: Treatment of high-grade dysplasia or early cancer with endoscopic resection", section on 'Pretreatment evaluation'.)
After performing an endoscopic inspection and classification of a visible lesion, the borders of the lesion are delineated to allow for complete ER. Optical chromoscopy provides enhanced endoscopic visualization of the subtle mucosal and vascular changes that occur in the progression of BE to esophageal cancer and allows for detailed inspection of the demarcation zone of an early lesion. Most advanced endoscopists use optical chromoscopy in addition to magnification to visualize the lesion's demarcation line because the lesion borders can be better appreciated with those methods (picture 3 and picture 4).
Despite the widespread use of optical chromoscopy by expert endoscopists for delineating a lesion prior to ER, data supporting this application of optical chromoscopy are limited. In a study including 68 patients with BE and single visible lesions (either high grade dysplasia or esophageal adenocarcinoma by histology), optical chromoscopy was associated with enhanced delineation of BE dysplasia compared with HD-WLE [10].
Follow-up after endoscopic therapy — For patients who had endoscopic therapy for dysplastic BE (eg, radiofrequency ablation [RFA]), the cornerstone of endoscopic follow-up consists of careful endoscopic inspection of the neosquamous mucosa and the neosquamocolumnar junction to rule out the presence of residual BE. (See "Barrett's esophagus: Treatment with radiofrequency ablation", section on 'Follow-up endoscopy'.)
We perform follow-up with HD-WLE and optical chromoscopy (NBI) to carefully inspect the tubular esophagus and gastroesophageal junction to exclude the presence of small islands of residual BE, recurrent IM, or dysplasia [9].
Optical chromoscopy can also be used in patients after RFA therapy for differentiating between residual islands of BE and erosions related to reflux esophagitis. (See "Clinical manifestations and diagnosis of gastroesophageal reflux in adults", section on 'Endoscopic findings'.)
CLASSIFICATION SYSTEMS BASED ON NBI — Classification systems for using narrow band imaging (NBI) to characterize the endoscopic appearance of BE have been developed, but studies evaluating their utility have been mixed. Although initial reports suggested that NBI can provide detailed inspection of the mucosal and vascular pattern of BE, studies were small and/or were performed by experts at single centers [12-15]. Subsequent validation studies of the resulting NBI classification systems have concluded that the classification systems were suboptimal [16-21]. As an example, in two studies evaluating the diagnostic accuracy of a simplified NBI classification system using still images, diagnostic performance was suboptimal and the interobserver agreement was moderate [16,21].
The diagnostic accuracy for NBI classification systems when they are used routinely for patients with BE has remained uncertain. The Barrett's International NBI Group developed a consensus-driven simplified NBI classification system for identification of dysplasia and cancer in patients with BE, resulting in 80 percent sensitivity, 88 percent specificity, 88 percent negative predictive value (NPV), and substantial interobserver agreement (kappa = 0.68) [22]. Likewise, another study using two experts and two nonexperts resulted in overall diagnostic accuracy values >90 percent using the simplified NBI classification based on NBI images with endoscopic magnification [23]. However, these studies were conducted in a selected patient cohort with high-quality images captured by expert endoscopists. More importantly, regions of interest containing low-grade dysplasia, indefinite for dysplasia, or erosive esophagitis/active inflammation were excluded. These regions may be less amenable to recognition by NBI and may therefore decrease sensitivity of NBI for predicting dysplastic BE.
SOCIETY GUIDELINE LINKS — Links to society and government-sponsored guidelines from selected countries and regions around the world are provided separately. (See "Society guideline links: Barrett's esophagus".)
SUMMARY AND RECOMMENDATIONS
●Advanced imaging technologies including optical chromoscopy allow for detailed endoscopic inspection in patients with Barrett's esophagus (BE). Preprocessing optical chromoscopy techniques, including narrow band imaging (NBI), blue light imaging (BLI), and optical enhancement (OE), highlight superficial mucosal and vascular structures and improve visualization of abnormalities that are suspicious for dysplasia. (See 'Introduction' above.)
●Optical chromoscopy allows for inspection of the mucosal surface and vascular pattern, is operator friendly, and does not require special dyes. (See 'Principles' above.)
●Surveillance high-definition white light endoscopy (HD-WLE) with random biopsies is the standard method for detecting intestinal metaplasia (IM) and dysplasia in patients with BE. Potential applications of optical chromoscopy in combination with HD-WLE include enhanced detection of BE dysplasia and identification of areas for targeted (rather than random) biopsies. More studies using optical chromoscopy techniques are needed to establish the diagnostic accuracy of this technique for detecting dysplastic BE in the general population. (See 'Detecting dysplasia' above.)
●Other potential applications for optical chromoscopy include assessing for subtle differences in mucosal relief, delineating a dysplastic lesion prior to endoscopic resection (ER), and examining the tubular esophagus and gastroesophageal junction after endoscopic therapy to identify residual BE islands. (See 'Clinical applications' above.)
●ER in patients with BE who have high-grade dysplasia or early cancer is discussed separately. (See "Barrett's esophagus: Treatment of high-grade dysplasia or early cancer with endoscopic resection".)
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