Magnification and Chromoscopy with the Acetic Acid Test: Reply to Dr. Kaufman and Dr. Harper

Chromoscopy with acetic acid - a technique that has been in use in the field of gynecology for a considerable period - may be equally valuable in gastrointestinal endoscopy. We are grateful to Dr. Kaufman and Dr. Harper for their analysis of the whitening reaction in the cervical mucosa; the information they provide supplements our previous description and provides further justification for the use of the technique in gastroenterological endoscopy.

Acetowhitening implies increased opacity in the mucosal surface; Kaufman and Harper consider that reversible alterations in the proteins (histones) and unwrapping of DNA in the cell nucleus are more important aspects of the process involved than the fasciculation of cytoplasmic cytokeratins. Permeability of the epithelial compartment to acetic acid is a precondition for acetowhitening, in which intracellular and extracellular mechanisms may play a role. The selective response of neoplastic cells may result from intracellular mechanisms increasing the permeability of these cells. Kaufman and Harper emphasize the role of extracellular mechanisms and explain the nonspecific reactions in the cervix through increased permeability at compromised cell junctions in the transformation zone, an immature metaplastic epithelium, and crypt openings. At the level of the columnar epithelium (in the endocervix), acetic acid (a membrane breaker) penetrates into the underlying stroma and its action is not limited to the monolayer cell compartment.

A transition from stratified squamous epithelium to columnar epithelium is also present in the upper gastrointestinal tract. The epithelial junction is located at the cardia, or misplaced proximally in the columnar-lined esophagus (Barrett’s esophagus). There are two distinct uses for chromoscopy in upper gastrointestinal endoscopy: firstly, the acetowhitening reaction in the squamous stratified epithelium can be used to detect neoplastic areas in the same way as in the cervix; secondly, it can be used to explore the segment of columnar metaplasia in Barrett’s esophagus. In this situation, acetowhitening is of limited value in comparison with the enhancement of the surface epithelial crests provoked by the congestion and swelling of the stroma after exposure to acetic acid. However, the procedure is useful for magnification analysis (80 ×) of the three distinct types of metaplastic epithelium and for detecting areas of specialized intestinal metaplasia and assessing the surface pattern of flat neoplastic areas. The morphological description of these patterns is promising, but still requires further analysis.