20/06/2024
Chromoendoscopy ๐ค๐ค
๐น๐นChromoendoscopy involves the topical application of stains or pigments to improve tissue localization,characterization, or diagnosis during endoscopy.
๐น๐นSeveral agents have been described that can broadly be categorized as absorptive(vital) stains (Lugol's solution and methylene blue) , contrast stains (indigo carmine), and reactive stains.
๐น๐นLugol's solution ยปcontains potassium iodine and iodine, which have an affinity for glycogen in normal non-keratinized squamous epithelium. An abnormal staining pattern(absence of dye uptake) is associated with conditions that result in depletion of glycogen in squamous cells, such as inflammatorychange (eg, reflux esophagitis), dysplasia, or early malignancy. Lugol's solution has a sensitivity of 91 to 100percent and a specificity of 40 to 95 percent.Lugol's staining may lead to a transient retrosternal discomfort. Severe allergic reactions have been reported.
๐น๐นMethylene blue is a vital stain taken up by normal intestinal epithelium.It does not stain nonabsorptive epithelia such as squamous or gastric mucosa. In the small intestine and colon, alack of staining suggests metaplastic, neoplastic, or inflammatory change, whereas in other areas of the gastrointestinal tract it is usedto identify metaplastic absorptive mucosa (eg, Barrett's mucosa).Pit patterns, which are highlighted by the methylene blue staining. Methylene blue staining involves the application of a mucolytic, followed by dye, followed by washing off excess dye. The reagents are sequentially sprayed onto the mucosa using a washing catheter. stable. Positive staining is defined as the presence of blue-stained mucosa that persists despite vigorous water irrigation. However, a concern has been raised regardingthe potential to induce oxidative damage to DNA in tissues exposed to methylene plus white light (which is used during endoscopy).
๐บ๐บIn clinical practice, electronic chromoendoscopysuch as NBI, combined with high-definition or magnification endoscopy, provides an accurate and efficient alternative to methylene bluechromoendoscopy.
๐น๐นIndigo carmine is derived from a blue plant dye (indigo) and a red coloring agent (carmine). It is the most common form of chromoendoscopy applied in the colon. It pools in crevices between epithelial cells, highlighting small or flat lesions and defining irregularities in mucosal architecture, particularly when used with high-magnification or high-resolutionendoscopy.
๐น๐นAcetic acid enhancement has also been applied in the gastrointestinal tract, and it is an inexpensive, simple, and accurate alternative to digital techniques that use optical or electronic enhancement. Application of acetic acid may help identify intestinal metaplasia in the esophagus and gastric cardia and help detect dysplasia or early cancer in patients with Barrett's esophagus. It acts as a mucolytic agent to enhance the visualization of the mucosal pattern with high-resolution endoscopy. Approximately 10 mL of 1.5 to 3 percent acetic acid is sprayed onto the esophageal wall. Initially, both the esophageal mucosa and the gastric mucosa turn white, but after two to three minutes, the normal esophagus remains white ("acetowhitening"), whereas Barrett's mucosa and gastric columnar mucosa will turn red. The criteria for recognizing neoplasia include focal loss of acetowhitening and surface patterns of Barrett's mucosa.
๐บ๐บData have suggested that there was no significant difference in dysplasia detection between dye-based chromoendoscopy and virtualchromoendoscopy (narrow band imaging).
LIMITATIONS of Chromoendoscopy ๐คซ๐ค๐ค
1. time-consuming.
2.Many endoscopists lack training in chromoendoscopy > a high level of interobserver variability
3.Lack of standardization.
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