Chromoendoscopy and Its Utilization

Introduction:

Diagnostic procedures are keys to successful treatment options. Through appropriate treatment diagnostic procedures, one can easily diagnose the underlying pathology and pinpoint the diseased part. Though image-based procedures have gained popularity over the years due to their non-invasive nature, direct visualization is still considered one of the gold-standard approaches. But, differentiating between healthy tissue and pathological condition through direct visualization is difficult and may lead to improper diagnosis. Chromoendoscopy is a procedure in which dyes are used to identify pathological conditions.

What Is Endoscopy?

Endoscopy is a procedure in which a camera-like device is inserted into the body with the help of a flexible tube-like structure. This helps in the visualization of the organs from the inside. Also, other structures can be attached to it for different diagnostic and surgical purposes. In gastroenterology, endoscopy can be used for the visualization of structures like the oropharynx, esophagus, stomach, and parts of the small intestine (proximal duodenum). This type of endoscopy is known as an esophagogastroduodenoscopy. The endoscopic procedure that is used to visualize the rectum, colon, and distal portion of the small intestine (terminal ileum) is known as a colonoscopy.

Traditional endoscopy and colposcopy are also known as white-light endoscopy. But, smaller details and tissue changes can be missed in this procedure. In the chromoendoscopy technique, stains or dyes are used to detect minor tissue changes. The endoscopic procedure can be utilized to take a high-resolution picture of the stained tissues. These high-resolution images can facilitate the detection of malignant changes in the tissues and structural changes. Also, magnified views of the tissue structures can be possible.

What Are the Indications of Chromoendoscopy?

Chromoendoscopy techniques can be used for the following purposes:

1. To detect dysplastic changes in inflammatory bowel disease. This procedure can be helpful in a targeted biopsy.

2. For surveillance purposes and in detecting malignant changes in polyposis syndromes (a condition in which multiple polyps are present throughout the gastrointestinal tract).

3. For the detection of pre-neoplastic changes in Barrett’s esophagus (thickening of esophageal lining due to acid reflux). Other than this, esophageal adenocarcinoma and squamous cell carcinoma can be detected using this technique.

4. Colorectal cancer can be diagnosed using this procedure.

5. This procedure can be used for screening purposes for ulcerative colitis.

What Is the Procedure of Chromoendoscopy?

Chromoendoscopy can be divided into two categories. One is dye-based chromoendoscopy, and the other is electronic or visual-based chromoendoscopy. In the dye-based procedure, a spring catheter is used to apply a fine mist of the dye on the gastrointestinal surface. In some cases, prior application of N-acetylcysteine is used as a coating agent to get rid of excess mucus. N-butylscopolamine can also be used to prevent peristalsis and uneven distribution of the dye.

During the application of the dye, the tip of the endoscope is slowly withdrawn. After that, the endoscopic tip with 1 to 2 centimeters of protruding spraying catheter moves in the spiral direction to spray the mist of the dye. An area of 20 centimeters is sprayed at a time to maintain the evenness of the dye. This also prevents dye pooling. After the endoscopic procedure, the dye is washed out. The dyes used for this purpose can be categorized into three categories. Vital dyes or absorbing dyes can be absorbed by the tissues. Lugol solution, methylene blue, toluidine blue, and cresyl violet. Contrast dyes can be used to detect stable surface changes. Such a dye is indigo carmine. Reactive dyes react with the cancerous tissues and help in the identification procedure. Phenol red and congo red are examples of such types of dyes.

What Are the Different Dyes?

Different dyes are used in the dye-based chromoendoscopy procedure. These dyes are:

1. Acetic Acid: This is a weak acid dye that causes the denaturation of tissue proteins. Such dyes can be used for the identification of dysplastic tissue changes. Around 20 milliliters of 1.5 to 3 percent of acetic acid is sprayed over the mucosal surface. A whitish discoloration of the mucus can be observed. Additionally, changes like irregular pitted surfaces and reticular patterns can be seen.

2. Methylene Blue: 0.5 percent of methylene blue is used as a dye. Such dyes can be absorbed by the epithelium of the small intestine and colon. Whereas, gastric mucosa does not absorb such dyes. A 10 percent solution of N-acetylcysteine can be used as a coating agent prior to the application of the dye. In the colonic mucosa, the concentration of methylene blue should be 0.1 percent. Oxidative damage of the tissues and bluish discoloration of urine are the usual side effects of this dye.

3. Cresyl Violet: This dye is used in combination with methylene blue to detect early cancerous changes. 0.05-2 percent of this dye is used for the staining of the small intestine. Other than this, the upper gastrointestinal tract can also be stained by this type of dye.

4. Lugol: This is an iodine-based solution that can be used to identify dysplastic changes. This iodine is taken up by the non-keratinized squamous epithelium cells. Healthy epithelium appears as reptile skin, whereas neoplastic epithelium does not take up any stain. Ideally, 1 to 2 percent Lugol’s solution is used. Severe allergic reaction is the main complication of this solution. A 5 percent sodium thiosulphate solution is used to reduce the side effects.

5. Indigo Carmine: This is a type of food dye that is used as a contrast dye. 0.4 percent of this dye is applied over the mucosal surface. Various patterns on the mucosa, like a round pit, reticular patterns, sulcus-like pits, and a tubular pattern, appear on the mucosal surface.

6. Congo Red: This dye changes its color with the change in the pH of the epithelium. In contact with an acidic environment, the color changes from red to dark blue. This is used to identify cancerous changes in the gastric mucosa. 0.3 percent to 0.5 percent concentration of staging solution is used. In some cases, it is used in combination with methylene blue.

7. Phenol Red: This dye changes its color from yellow to red in the presence of an alkaline environment. 1 percent phenol red in combination with 5 percent urea is spread over the surface. This dye is accurate in detecting Helicobacter pylori infections. Increased gastric motility is the potential complication of this dye.

What Are the Adverse Reactions?

The potential adverse reaction caused by the dyes is a severe allergy, increased gastric motility, and tissue damage. Some dyes may cause DNA (deoxyribonucleic acid) damage and epithelial cell damage if applied in higher concentrations. Lugol’s solution may cause thyrotoxicity.

Conclusion:

Endoscopy is an important diagnostic procedure for visualizing underlying structures. But, minor tissue changes or area-specific changes can not be visualized. Chromoendoscopy techniques utilize dyes to stain tissues. Early cancerous changes in the tissues can be visible in this technique.