Chromoendoscopy involves the spraying of transient pigments or dyes onto the GI mucosa during an endoscopy procedure to aid in tissue diagnosis and characterization. In particular, it has been used to identified areas of dysplasia (precancerous cells) or cancer that are not easily visible with standard endoscopic imaging. The agents sprayed work by being absorbed by certain tissue types, serving to highlight topographical features and tissue irregularities or undergoing a chemical reaction with specific cell or tissue types that create a visible change in color. In the esophagus, Lugol’s solution is often used to identify squamous dysplasia or cancer. It is absorbed by normal squamous tissue and has reduced to absent absorption in dysplastic tissue or cancer. Methylene blue staining is typically used to assess areas of Barrett’s esophagus, with decreased uptake noted in areas of dysplasia/early cancer when compared to non-dysplastic Barrett’s epithelium. Acetic acid has also been used to aid in the detection of dysplasia within a region of Barrett’s esophagus.
Optical chromoendoscopy is a conceptually similar method by which optical light filters or digital imaging processing performed by the endoscope can, at times, achieve nearly comparable results to spray chromoendoscopy. This technique is similar, more efficient and likely subject to less variability in interpretation compared to spray chromoendoscopy.
Chromoendoscopy is relatively inexpensive to perform and the necessary equipment can be found in most endoscopy units. However, it can be time consuming and the results can vary widely among endoscopists. It is primarily used to aid in the detection of abnormal and usually precancerous tissue in the esophagus and helps to define the margins of these lesions to aid in their resection.