Chromoendoscopy

Chromoendoscopy is a complementary imaging technique that is used in conjunction with a gastroscopy or colonoscopy to improve the visualisation of certain changes in the digestive tract mucosa. It can be carried out by applying a substance to the surface or by activating an electronic system that modifies the image. Its aim is to help locate, characterise or delineate lesions and select the most suitable areas for taking biopsies.

What is chromoendoscopy and what information can it provide?

During an endoscopy, the specialist examines the mucosa using high-definition white light. In certain situations, they may use a staining technique to better distinguish differences in colour, texture, surface or vascularisation.

Chromoendoscopy can be used on a specific area or whilst examining a larger section. Its purpose is to complement the endoscopic examination. It can help to detect a subtle abnormality, study its characteristics or better identify its margins, but it does not in itself confirm a microscopic diagnosis.

A suspicious image may require a biopsy, resection, follow-up or specialist assessment.

Types of chromoendoscopy

There are two main types, which use different principles.

Chromoendoscopy with substances

This involves applying a solution to the mucosa via the endoscope. Some substances highlight the surface texture, whilst others cause temporary colour changes in certain tissues.

Substances used in specific situations include indigo carmine, acetic acid and Lugol’s solution. Each has specific indications and precautions and they are not interchangeable.

Virtual or electronic chromoendoscopy

This does not use dyes. The endoscope applies optical filters or digital processing to highlight colour differences, vascular patterns and surface characteristics.

These technologies include NBI, BLI, LCI and i-scan. Their availability depends on the equipment used. During the same examination, the specialist can switch between conventional imaging and electronic enhancement.

In what situations can chromoendoscopy be used?

The technique is used when a more detailed examination of the mucosa can provide information relevant to diagnosis, monitoring or treatment planning.

Monitoring of inflammatory bowel disease

In certain people with ulcerative colitis or Crohn’s disease affecting the colon, chromoendoscopy may form part of the monitoring for dysplasia and colorectal cancer. The approach depends on the duration and extent of the disease, the level of inflammation, the patient’s medical history and other risk factors.

Severe inflammation may make interpretation difficult and necessitate adapting or repeating the examination.

Barrett’s oesophagus

During the monitoring of Barrett’s oesophagus, acetic acid or virtual chromoendoscopy can help to identify areas requiring more detailed examination.

These techniques are incorporated into surveillance protocols and do not generally replace biopsies when these are indicated.

Assessment of gastric and colonic lesions

In the stomach, enhancement techniques can help identify changes in the mucosa, guide biopsies and delineate certain superficial lesions. In the colon, they can facilitate the assessment of the surface pattern, the vessels and the margins of polyps or other lesions.

They can also be used to examine scars from previous resections or to plan certain endoscopic procedures.

Detecting, characterising and localising a lesion

Chromoendoscopy can be used for various purposes.

• Detection involves locating an abnormality that was not clearly discernible during the initial examination.

• Characterisation involves studying its surface pattern or vascularisation to assess its possible nature.

• Delimiting means identifying more precisely where the lesion begins and ends.

These functions help to guide clinical decisions, but do not amount to confirming the diagnosis through tissue analysis.

How to prepare for a chromoendoscopy

Preparation depends on the main endoscopy during which it is to be carried out.

If it is carried out during a colonoscopy, you must follow the instructions regarding diet, bowel-preparation solution, fluids and fasting provided by the Digestive Endoscopy Unit. Thorough bowel cleansing is particularly important because residual material can obscure lesions or make it difficult to assess the mucosal patterns.

If it is performed during a gastroscopy, the specific instructions regarding food, fluids and fasting must be followed. Chromoendoscopy on its own does not usually require any additional changes to medication. However, the management of anticoagulants, antiplatelet agents or other treatments may depend on whether biopsies or a resection are planned.

Treatments should not be altered on one’s own initiative.

How a chromoendoscopy is performed

The specialist usually begins by examining the mucosa using high-definition white light. When a substance is used, they may first clean the surface to remove mucus, foam or debris. They then apply the solution via a small catheter inserted through the endoscope’s channel.

Depending on the product, it may be necessary to wait a few moments, rinse or suction off the excess, and re-examine the area. In virtual mode, the specialist activates the image processing system using the endoscope controls. No substance is added.

The practitioner can switch back and forth several times between the conventional image and the enhanced view to compare the findings. When an abnormal area is identified, it can be examined in greater detail, imaged, biopsied, removed where appropriate, or documented to plan a subsequent procedure.

What you might feel during a chromoendoscopy

The experience depends mainly on the gastroscopy or colonoscopy during which it is used. It may involve fasting or bowel preparation, sedation, insertion of the endoscope, distension with gas or water, taking biopsies and subsequent recovery.

Most people do not notice when virtual enhancement is activated or when a substance such as indigo carmine is applied. The examination may take a little longer as it is necessary to clean and examine the mucosa with particular care.

Some substances used in the oesophagus may cause irritation, coughing, nausea or temporary discomfort behind the breastbone. The experience depends on the product used and the area being examined.

Biopsies and treatments during chromoendoscopy

Chromoendoscopy can help to identify the areas where a biopsy is most useful. A targeted biopsy does not always guarantee a definitive result. The sample may be insufficient, superficial or unrepresentative.

In certain screening programmes, targeted biopsies of visible lesions may be combined with samples taken from other areas in accordance with a protocol. A lesion may be excised during the same session when it is well characterised, treatment was planned, and the team considers that it can be performed appropriately.

Large, scarred, hard-to-reach lesions, or those suspected of deep invasion, may require further investigation, advanced techniques or a multidisciplinary assessment.

What information do the results of a chromoendoscopy provide?

The results are included in the report on the gastroscopy or colonoscopy.

No suspicious areas are identified

This means that no significant visible abnormalities were observed using the techniques employed. This reduces the likelihood of certain detectable lesions, but does not completely rule out microscopic changes, hidden areas or very subtle lesions.

An abnormal area is identified

The specialist describes its location, size, shape, surface, vascular pattern and margins. The finding may lead to a biopsy, a resection, follow-up or a specialist assessment. A suspicious image does not in itself constitute a confirmed diagnosis.

The image does not allow for sufficient characterisation

This may occur when there are residual tissue, bleeding, severe inflammation, scarring, previous procedures or poor image quality. In these situations, biopsies, a repeat examination or a specialist assessment may be necessary.

Limitations of chromoendoscopy

The usefulness of the technique depends on the organ and condition being examined, the modality used, the quality of preparation and the equipment. Other factors that influence its usefulness include the presence of inflammation or scarring, the time spent on the examination and the practitioner’s experience.

Not all substances or electronic platforms are equally useful in all situations. Contrast enhancement may improve visualisation in specific contexts, but it does not guarantee the detection of all lesions, nor does it generally replace histopathological examination.

Risks and possible effects of chromoendoscopy

Most of the risks stem from the gastroscopy or colonoscopy itself, from sedation, and from any biopsies or treatments carried out. Depending on the procedure, these may include bleeding, perforation, aspiration, or respiratory or circulatory complications related to sedation.

The specific effects of the substances depend on the product used and the area to which they are applied. Some may cause local irritation, coughing, nausea or temporary discomfort. Hypersensitivity reactions are rare, but any relevant medical history should be disclosed.

Virtual chromoendoscopy does not involve additional exposure to substances, although it carries the risks inherent in endoscopy and the procedures performed during it.

When to seek a follow-up consultation after the examination

The post-procedure recommendations depend on whether a gastroscopy or colonoscopy was performed and on any procedures carried out. You should seek medical assessment if you experience:

• Severe or worsening pain.

• Heavy bleeding.

• Fever.

• Difficulty breathing.

• Persistent vomiting.

• Severe dizziness or fainting.

• Marked abdominal distension.

• General deterioration.

The Digestive Endoscopy Unit should provide instructions tailored to the procedure performed.

Chromoendoscopy and other endoscopic imaging techniques

Chromoendoscopy can be used in conjunction with high-definition white light, optical magnification, guided biopsies, echoendoscopy and histopathology. Each provides different information.

White light allows for a general inspection of the mucosa. Chromoendoscopy helps to examine the surface and blood vessels in greater detail. Echoendoscopy enables the assessment of the deeper layers of the digestive tract wall and nearby structures.

Pathology examines the microscopic characteristics of the tissue. The use of multiple technologies does not automatically improve the diagnosis. The choice of which to use depends on the information the medical team needs to obtain.

Specialists in chromoendoscopy at the Publio Cordón Memorial Hospital

At Publio Cordón Memorial Hospital, chromoendoscopy forms part of the Digestive Endoscopy Unit, within the Department of Gastroenterology. The unit carries out diagnostic and therapeutic endoscopy, as well as advanced procedures for the investigation and treatment of digestive disorders.

Dr Javier Aranda Hernández, head of the Digestive Endoscopy Unit, specifically includes chromoendoscopy and high-definition endoscopy amongst the techniques he routinely performs. His practice is particularly focused on the early detection of lesions, oncological endoscopy and the endoscopic treatment of complex digestive lesions. ()

When biopsies are taken or lesions are removed, histopathological analysis completes the interpretation of the endoscopic findings.

Medical information for general guidance

This factsheet aims to help you understand what chromoendoscopy is, how it is carried out during a gastroscopy or colonoscopy, the different types available, and what information it can provide to locate, characterise or define specific digestive lesions.

The Publio Cordón Memorial Hospital promotes accurate, understandable and useful medical information, linked to specialist care, research, scientific dissemination and advances in medicine.

The indication for chromoendoscopy, the technique used, patient preparation, biopsies and the interpretation of findings must be tailored to the clinical situation and the main endoscopy procedure. A suspicious endoscopic finding must be considered in conjunction with the rest of the assessment and, where indicated, with tissue analysis.