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Chromoendoscopy
Medical expert of the article
Last reviewed: 05.07.2025
Chromoendoscopy is used for differential diagnostics of diseases that are difficult to distinguish by endoscopic signs. Most often, this concerns benign and malignant diseases, especially early forms, as well as determining the true boundaries of tumor lesions and inflammatory-degenerative changes in the mucous membrane. Methylene blue, Congo red, indigo carmine, Lugol's solution, Evans blue are used as dyes.
The effectiveness of vital dyes is based on such properties as contrasting, biological, chemical and fluorescent effects on tissues. Due to contrasting, the relief of the mucous membrane of organs is enhanced when a dye is applied to it (methylene blue, indigo carmine, Evans blue). Biological effect means the penetration of dye through the cell membrane into the cytoplasm and in vitro staining (methylene blue). The dye (Congo red, neutral red, Lugol's solution) can enter into a chemical reaction with the substance of epithelial cells and secretion that has an appropriate pH level, based on which one can judge the functional state of the organs.
Direct and indirect methods of chromoscopy are used.
In direct chromoscopy methods, the dye is applied to the surface of organs directly during endoscopic examination through a catheter or the instrument channel of the endoscope. The dye can be sprayed either targeted or totally. In this case, diagnostic errors (false positive results) are possible due to the fact that not only the organ tissue is stained, but also a number of other structures (fibrin, mucus). Careful preparation of the organ before applying the dye (mechanical cleaning, dissolution and removal of mucus, neutralization of the environment, etc.) helps to avoid these errors.
Indirect methods of chromoscopy are based on the introduction of a dye into the lumen of the organ being examined before the endoscopic examination: the patient can drink the dye solution or it is introduced through a probe. As with the use of direct methods, preliminary preparation of the mucous membrane for staining is necessary to obtain more accurate results.
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