Chromoendoscopy Technique

Updated: Sep 14, 2017
  • Author: Kondal Rao Kyanam Kabir Baig, MD; Chief Editor: Kurt E Roberts, MD  more...
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Technique

Approach Considerations

The agents used in chromoendoscopy are commercially available and inexpensive. They are not specifically made for endoscopy. They are prepared and diluted in accordance with the practices of the chromoendoscopists. Common staining agents used are Lugol solution, methylene blue, toluidine blue, crystal violet, indigo carmine, congo red, and phenol red. Special spray catheters are used to spray a fine mist on to the mucosa. [1]

The agents are classified as absorptive, contrast, or reactive agents. Absorptive stain are absorbed by or diffuse into specific cells. Contrast agents seep between cells and enhance the surface. Reactive agents undergo chemical reactions with specific cell components and undergo color change. [1]

It should be kept in mind that Lugol iodine can cause esophagitis or gastritis in rare cases. Hyperthyroidism or hypersensitivity to iodine should preclude the use of this agent. Methylene blue can cause discoloration of urine and feces. No serious adverse effects of other vital dyes have been described. General precautions should include aspiration and contact precautions. [1]

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Use of Staining Agents in Endoscopy

Application of some staining agents requires the application of mucolytic agents such as N-acetylcysteine to remove mucus from epithelium to allow optimal results with staining.

The agent may be applied to a specific area or to the whole mucosal surface of interest. The abnormal mucosa may stain positively (ie, taking up the dye) or negatively (ie, remaining unstained or understained). In general, the minimum amount of dye required is used. Excess dye is suctioned or washed. The time required for optimal staining is variable and depends on the targeted tissue and the stain used.

Table 1 below details the properties and uses of each agent. [1]

Table 1. Properties of and Clinical Indications for Common Stains Used in Endoscopy [1] (Open Table in a new window)

Stain Property Clinical Indication
Absorptive    
Lugol solution (iodine and potassium



iodide)



Glycogen-containing normal squamous



epithelium is stained dark brown;



inflammation, columnar mucosa, dysplasia,



and cancer remain unstained



Esophageal squamous cell cancer and



dysplasia



Barrett esophagus



Methylene blue (methylthioninium



chloride)



Absorptive epithelial cells of the small



bowel, colon, and intestinal metaplasia at



any site are stained blue; dysplasia and



cancer is variably stained or unstained



Barrett esophagus



Gastric intestinal metaplasia and cancer



Chronic ulcerative colitis



Toluidine blue (tolonium chloride) Nuclei of malignant cells are stained blue Oral and esophageal squamous cell cancer
Crystal violet (methylrosaniline chloride Absorbed into intestinal and neoplastic



cells; nuclear stain



Barrett esophagus



Colonic neoplasms



Contrast    
Indigo carmine (indigotindisulfonate



sodium)



Nonabsorbed dark bluish dye highlighting



mucosal topography



Colonic neoplasms



Chronic ulcerative colitis



Reactive    
Congo red (biphenylenenaphthadene



sulfonic acid)



Color change from red to dark blue/black



in presence of acid at pH 3



Ectopic gastric mucosa



Gastric cancer



Adequacy of vagotomy



Phenol red (phenolsulfonephthalein) Color change from yellow to red in



presence of alkali (eg, from hydrolysis of



urea to ammonia and carbon dioxide by



urease-producing H. pylori)



H. pylori infection

Chromoendoscopy is not an advanced endoscopic technique and is not technically difficult to learn. However, interpretation of the staining patterns requires training and may not always be easy. There is evidence that there is significant intraobserver and interobserver variation. [46, 47]

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