What is acid reflux?

In some patients with GERD, the squamous epithelium of the distal esophagus is replaced by specialized columnar epithelium, resembling that of the intestine and containing goblet cells. Although Dr. Norman Barrett thought this lesion was a congenitally shortened esophagus, studies consistently show that these patients have severe GERD with low LES pressures, poor esophageal motility, large hiatal hernias, and extensive acid and bile reflux. Furthermore, most patients have had chronic reflux symptoms for at least 10 years. Animal experiment show that, if the mucosal lining of the distal esophagus is excised in the setting of free acid reflux, columnar epithelium will regenerate in the area previously occupied by squamous epithelium. If reflux is controlled, the mucosal lining will regenerate with squamous epithelium. Pluripotential stem cells derived from the stratified squamous epithelium are the origin of the specialized columnar epithelium.

Barrett esophagus was once considered an uncommon condition, but estimates of its frequency at autopsy (1 in 57 to 1 in 105 cases), on general endoscopy survey (1 in 100 cases) and on endoscopic surveys of patients with GERD (10 in 100 to 15 in 100 cases), indicate that it is not uncommon, and it affects nearly 700,000 adults in the United States. An autopsy series from Olmsted County, Minnesota found that most cases of Barrett esophagus go undetected during life and thus are not accessible for cancer surveillance programs. Barrett esophagus is principally a disorder of white men; it is three times more frequent in men than in women and is rare in African Americans and Asians. It is found predominantly in middle-aged and older adults; the mean age at diagnosis is approximately 55 years, but it has been reported in children older than 5 years of age. The prevalence of Barrett esophagus increases with age, paralleling that of reflux esophagitis, but the length of the columnar-lined segment remains remarkably stable, even over years of endoscopic follow-up. This finding suggests that it arises rapidly in the susceptible reflux damaged esophagus and early in the course of disease. Families have been reported with multiple members having Barrett esophagus, some with cancer affecting more than one generation. Although the columnar-lined esophagus in itself does not cause symptoms, most patients complain of heartburn and regurgitations. Approximately 25% of patients with Barrett esophagus discovered at endoscopy have no esophageal symptoms.