Description

Ongoing technological developments in endoscopy have led to
an ever improving evaluation and management of digestive
diseases. The recent development of new of high-power
magnification or zoom endoscopes has boosted interest in
this technique, which has become increasingly available to
the modern gastroenterologist. Magnification is often used
in conjunction with chromoendoscopy in order to improve
the detection and diagnosis of neoplastic tissue. Currently,
the main clinical indications are the diagnosis of Barretts
oesophagus, the colonoscopic surveillance of colonic polyps
and the assessment of disease severity or the presence of
dysplasia in inflammatory bowel disease. Contrast stains
are most commonly used in combination with magnification
because they serve solely to highlight the mucosal architecture
and improve the discriminative properties of magnification.
Indigo carmine is the most frequenfly used contrast stain.
Examples of absorptive stains include methylene blue, which
stains small intestinal and colonic epithelium. Methylene
blue is used to identify intestinal metaplasia (IM) and to
screen for dysplasia in the oesophagus and stomach, as well as
for the detection of colonic adenomas. The detection of IM in a
columnar lined distal oesophagus is, because of its malignant
potential, crucial in the current definition of Barretts
oesophagus. With chromoendoscopy an attempt is made to
identify IM and possibly dysplastic changes in the Barretts
segment, in order to avoid unnecessary surveillance and to
minimize the number of unnecessary biopsies and sampling
error. Screening for colorectal neoplasms by colonoscopy is an
important means of preventing cancer, although as many as
27% of small adenomas may be missed during colonoscopy.
Non-polypoid, i.e. flat or depressed-type adenomas, are
especially easy to miss, but may harbour a greater potential to
malignancy than polypoid lesions. Chromoendoscopy, may
help in the detection of small adenomas and in differentiating
neoplastic from non-neoplastic polyps. The screening for
dysplasia in long-standing inflammatory bowel disease is
another interesting indication for pan-chromoendoscopy.