Chromoscopy of Intestinal Metaplasia in Barrett's Esophagus

Objectives

Barrett's esophagus is a metaplastic change which occurs in the esophagus due to chronic gastroesophageal reflux disease. It is currently diagnosed by the histological identification of characteristic “distinctive” intestinal-type metaplasia with characteristic crypts and villi lined by mucus-secreting columnar cells and goblet cells (or specialized columnar epithelium) in samples from columnar-lined esophagus. Although gastric-type metaplasia may be visualized as pink, columnar mucosa in the distal esophagus, it is the specialized columnar epithelium, which is pathognomonic of Barrett's esophagus and associated with the increased risk of adenocarcinoma.

Previous definitions of Barrett's esophagus were based on the length of columnar mucosa. However, the most accepted current definition is the presence of specialized columnar epithelium of any length in the tubular esophagus. Hence, identification by methylene blue chromoendoscopy of this distinctive intestinal-type metaplasia in a short length of columnar epithelium could help direct biopsy and increase the accuracy of diagnosis of Barrett's esophagus [1] [2] [3] (Figure [1]). It is superior to random biopsy in diagnosing specialized Barrett's epithelium that is greater than 1 cm (i. e. irregular Z line) and less than 3 cm. In a controlled study, the proportion of patients with biopsy-proven intestinal metaplasia increased from 45 % when random biopsy was used to 77 % when methylene blue chromoendoscopy was used (P = 0.03), in those with 1 to < 2 cm of columnar mucosa [3]. In patients with 2 to < 3 cm of columnar mucosa, the proportion with biopsy-proven intestinal metaplasia increased from 58 % to 90 % when methylene blue-directed biopsy (P = 0.02) was used [3]. Furthermore, methylene blue chromoendoscopy can identify short Barrett's esophagus with fewer biopsies than random biopsy [1] [3]. The diagnosis of short Barrett's esophagus and visualization of minute areas of columnar mucosa in the distal esophagus can potentially be further improved by high-resolution or high-magnification endoscopy (Figure [2]) [4].

Figure 1 Distal esophagus and gastroesophageal junction of a patient with < 1 cm of columnar mucosa in tongues and islands and no diagnosis of Barrett's esophagus (a). After methylene blue chromoendoscopy (b), focal dark blue staining of intestinal metaplasia was visualized without magnification under the Z line and in a small island just above it. Directed biopsies from these areas showed intestinal metaplasia.

Figure 2 Unmagnified (a) and magnified (b) views of the distal esophagus and gastroesophageal junction showing short Barrett's esophagus following methylene blue chromoendoscopy. The unmagnified endoscopic image (a) shows blue staining of specialized epithelium (yellow arrow) within the short tongues and under the Z line (a). Magnification (35 ×) with an Olympus zoom endoscope (b) resulted in improved visualization of more numerous tiny islands, some not appreciated without magnification, including one with a tiny area (white circle in a) of focal dark blue staining (yellow arrow). Directed biopsies from these areas showed intestinal metaplasia.

Barrett's esophagus is one of the few identifiable precursors to adenocarcinoma of the esophagus, a malignancy which is occurring in epidemic proportions in North America and Europe. Endoscopic surveillance is recommended but there is no consensus about the optimal technique for performing surveillance biopsy in the United States. Methylene blue chromoendoscopy has also been used to improve the accuracy and cost-effectiveness of detecting dysplasia and early cancer during routine surveillance [1]. Fewer biopsies are required because highly dysplastic cells (unstained by methylene blue) can be preferentially targeted and the diagnostic yield can be significantly improved, particularly for high-grade dysplasia and inapparent early cancers without an associated lesion [1] [5]. Furthermore, abnormal methylene blue staining is an excellent marker of severe dysplasia or early cancer, even in the presence or absence of any mucosal abnormality. Hence, it can identify patients who need aggressive biopsy for detailed mapping of dysplasia prior to endoscopic therapy.

References

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