Chromoendoscopy is an auxiliary method to endoscopy, which is used especially in gastroenterology. The term is based on the prefix chromo- (color) and suffix –endoscopy. Endoscopy means examination of a hollow organ by a rigid or flexible tube, which is usually equipped with a video camera and source of light. 


This test improves endoscopic techniques such as upper GI endoscopy and colonoscopy. During these tests, a special applicator is inserted into the gastrointestinal tract through the endoscopic device. This applicator delivers the dye substance on the local mucous membrane. Some dyes show the mucosal relief; others are actively absorbed by certain mucosal cells.

The video camera located at the end of the endoscopic device visualizes the colored mucosa. This method helps to increase the chance of diagnosis certain mucosal changes that may be present in precancerous conditions, or early forms of gastrointestinal cancers.


There are several commonly used dyes that are used in certain indications:

Lugol's solution

This brown liquid containing iodine is most commonly used in the esophagus. When sprayed, the healthy esophageal mucosa turns brown. Mucosa affected by inflammation or precancerous lesions however do not change its color properly as the cells do not accumulate the dye. The method is great in finding dysplastic precancerous lesions invisible to naked eye, esophageal cancer and Barrett's esophagus.

Methylene blue

This dye colors the mucous membranes of the digestive tract to blue. The dye is less absorbed in precancerous mucosa and mucosa of inflammatory lesions that are therefore lighter than neighboring healthy mucosa.


This dye is preferably used in the colon. It does not absorb into the cells, but it “only” seeps into mucosal crevices and allows the physician to better see any mucosal changes. The main aim is to better visualize any precancerous or tumor lesions.

Acetic acid

This is not a typical dye, but when applied to the mucosa of Barrett's esophagus, it produces whitish color in precancerous mucosa due to local chemical reaction.

Congo red

This dye is red, but it turns black after contact with acidic environment because of a chemical reaction. It is used to evaluate gastric acidity, which may be decreased when taking proton pump inhibitors or because of some chronic inflammations of the stomach.


The current preparation before the procedure depends on the endoscopic method, during which the chromoendoscopy is performed (upper GI endoscopy, colonoscopy).


There are relatively few disadvantages of these methods. Lugol's solution sometimes causes nausea and relatively rarely it may be accompanied with allergic reaction. Methylene blue is well-absorbed by the intestinal mucosa, it enters the blood stream and it may turn the patient's urine blue.


Chromoendoscopy is a very elegant supplementary examination to endoscopy, which improves the visibility of certain pathological changes (usually precancerous), even in apparently healthy mucosa. This enables the doctor to take tissue samples for histological examination. Chromoendoscopy increase chance of diagnosing any malignant disease either in precancerous stage, or in phase of an early cancer when it can be treated by endoscopic intervention.


Jiri Stefanek, MD  Author of texts: Jiri Stefanek, MD
 Sources: basic text sources