How frequently is the diagnosis of Barrett's mucosa missed at the time of endoscopic examination?
E. Achkar (Cleveland)
The diagnosis of Barrett's epithelium is generally based on discovery of a salmon-pink colored mucosa during endoscopy with histologic confirmation of the presence of columnar epithelium. Biopsies taken too close to the esophagogastric junction might represent gastric tissue resulting in the false diagnosis of Barrett's mucosa. Because it is sometimes difficult to distinguish the end of the esophagus from the most proximal part of the stomach and because the Z-line is not always clearly demarcated, it is routinely accepted that biopsies should be obtained 2-3 cm above the esophagogastric junction. A new definition of Barrett's mucosa is emerging, limiting the condition to the presence of intestinal metaplasia since it seems that only this kind of epithelium is associated with an increased risk of malignancy . If this definition becomes universal and goblet cells become the hallmark of significant metaplasia, the scope of Barrett's esophagus (BE) will be narrowed in the future. However, at the present time and from the endoscopist's point of view, the practical approach is to recognize the color changes in the lower esophagus and obtain biopsies from appropriate sites.
How accurate is the endoscopic diagnosis of Barrett's mucosa? In most cases, the familiarity with the different landmarks, recognizing the level of the diaphragm and avoiding the hiatal hernia sac lead to easy recognition of Barrett's esophagus particularly when the length of metaplastic mucosa extends over 3-4 cm. The presence of reflux esophagitis, mid-esophageal strictures, or ulcers raises the index of suspicion. A new endoscopic criterion has been suggested, using the proximal margin of the gastric folds as a landmark and obtaining biopsy specimens 2 cm above that level. A study of 18 patients showed that columnar lined epithelium was obtained 2 cm above the proximal margin of the gastric folds of a hiatal hernia pouch in all patients . Instillation of a coloring solution to stain the columnar epithelium such as toluidine blue has been used to increase the yield of detection  but this technique has not received wide acceptance. In a recent study, Kim et al. , showed inconsistency in locating the lower esophageal sphincter both manometrically and endoscopically. The mean values of endoscopic and manometric lower esophageal sphincter measurements were consistent within six weeks but individual changes were common from examination to the next. About 10% of patients had a change greater than 4 cm on endoscopy and manometry between examinations. A population study of Barrett's esophagus in Olmsted County, Minnesota revealed the prevalence of 22.6 cases per 100,000 inhabitants. A search for the same diagnosis in autopsy material showed a 21-fold increase in prevalence . Results such as these indicate that endoscopy tends to underestimate the frequency of Barrett's mucosa and that many cases remain unrecognized.
The concept of short segment Barrett's esophagus introduced recently constitutes another source of doubt as to the ability to diagnose columnar lined epithelium with precision. Spechler et al.  obtained biopsies in 142 patients who had columnar epithelium for less than 3 cm in the distal esophagus and found specialized intestinal metaplasia in 18%. According to the traditional definition of Barrett's esophagus these patients would remain unrecognized. A recent study showed that specialized columnar epithelium is seen frequently around the cardia with or without the presence of columnar lined esophagus . The authors suggested that short segment BE and intestinal metaplasia of the cardia should be grouped under a single concept. Another study revealed the prevalence of short Barrett's esophagus in 32% of patients . Only 4 out of 130 patients had long segment Barrett's esophagus. Symptoms of reflux were similar in patients with short segment Barrett's esophagus and those without Barrett's esophagus . A third study revealed inconsistencies from one examination to another in diagnosing short segment Barrett's esophagus . The impact of short segment Barrett's esophagus on the accuracy of the diagnosis is not known yet and awaits further studies. It is not possible to determine the exact accuracy of the endoscopic diagnosis of Barrett's epithelium with precision. The evolving definition of Barrett's mucosa and the changing emphasis on the predisposition to cancer from one kind of epithelium to another will certainly have a direct impact on detection in the future. For the time being, endoscopists should continue to exhibit an appropriate index of suspicion, develop familiarity with the endoscopic landmarks and obtain biopsies 2-3 cm above the esophagogastric junction until more studies determine the clinical significance of short segment Barrett's esophagus.