Magnification and Chromoscopy with the Acetic Acid Test

Gastroscopy and Colposcopy

The secondary prevention of female genital neoplasia, and of digestive neoplasia in both sexes, is based on early detection at the preinvasive stage. In the absence of conspicuous alterations of the mucosa, highly sophisticated techniques (spectroscopy, optical coherence tomography) have been developed for the purpose; however, their high cost and complexity is not compatible with widespread use in everyday practice. A technology combining a high level of optical resolution with a magnification system provides a more accessible option.

The most recent video-endoscopes available for digestive endoscopy offer the high resolution of a digital processor and magnification with the optical zoom. “In-contrast” magnification explores the mucosal surface of the digestive tract with the help ofa dye (chromoscopy). “In-transparency” magnification explores the microvascular network under the translucent mucosal surface, without staining; the irregularities and the caliber of the vessels increase with the progression of neoplastic angiogenesis. Magnification endoscopy was developed in Japan in a sequence of technological advances. The “in-contrast” technique revitalized the indications for chromoscopy, with nonabsorbed dyes (indigo carmine) or absorbed dyes (Lugol, methylene blue, crystal violet, cresyl violet). Distinct surface patterns in the digestive-tract mucosa have been described in the esophagus, gastric fundus, gastric antrum, duodenum, and colon. Disorganization of the so-called “pit pattern” in neoplasia has been categorized [1] in an approach to optical biopsy using in-contrast observation. Neoplastic angiogenesis has been also categorized [2] [3] using in-transparency observation. The new standard for exploration is starting to become available in routine endoscopy; however, most digestive endoscopists do not anticipate that the new generation of instruments will represent a revolution in endoscopic diagnosis.

A multidisciplinary approach might help change digestive specialists’ views. Gynecologists have been using chromoscopy and magnification routinely for 40 years now with the simple colposcope [4]. The colposcope was developed by Hinselman in the 1920 s, as a stereo microscope providing illuminated magnification (× 6 - 40) for exploration of the female genital mucosa. Colposcopy is used for diagnostic triage of women with positive cervical cytology and other screening tests, and also for directing biopsies and treatment. There are specific favorable conditions that explain this - the target area has no motility and is easily accessible with a rigid instrument; the mucous layer, impairing observation, is easily rubbed off. During colposcopy, in-contrast magnification uses an apparently very simple chromoscopy agent, acetic acid; however, this test is more sophisticated than was initially thought. In-transparency magnification, with the help of a green filter that contrasts the vessels in black, makes it possible to obtain very precise assessments of vascular abnormalities [1]. A further comparison with gynecology should be mentioned here - a squamocolumnar epithelial frontier is present at the esophagogastric junction and also at the junction between the endocervix and the ectocervix. At both junctions, a sharp discontinuity in pH occurs - neutral pH in the esophagus and acidic pH in the stomach, and acidic pH in the vagina (at pH 4) and neutral pH in the endocervix. Two types of tumor occur at both junctions - squamous carcinoma and adenocarcinoma. At both junctions, there is a trend toward an increasing frequency of adenocarcinoma.

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