What is Barrett’s disease or Barrett’s esophagus?

Barrett’s disease or Barrett’s esophagus is a condition wherein the esophageal mucosa transforms into a type of stomach or intestinal mucosa. The muscosa is called "metaplasia". There are 2 types of Barrett’s esophagus: inborn and acquired.
Inborn Barrett’s esophagus is present in children and it is believed to represent a disturbance during embryogenesis (ectopy).
Acquired Barrett’s esophagus an inflammatory genesis (begins with inflammation) and is typical for people over 50. Acquired Barrett’s esophagus is caused by the repeated reflux of stomach acid into the esophagus. Stomach acid can cause chronic erosive inflammation of the esophagus (esophagitis) in the lower third of the esophagus. Repeated esophagitis, over time, can cause transformation of the esophageal squamous epithelium into a cylindrical shaped cell, similar to the epithelium in the stomach or intestines (metaplasia). That’s why Barrett’s esophagus is 3-5 times more common in people who have gastro-esophageal reflux disease (GERD) than in those who don't. In your case, GERD may be caused by the hiatus hernia that you report as a pre-existing condition. Barrett’s esophagus doesn't cause any symptoms, but the symptoms of GERD (heartburn) or diseases that caused GERD (hiatus hernia, chronic gastritis, peptic ulcers…) are present. Smoking is not related with developing Barrett’s esophagus.
Metaplasia is often followed by epithelial dysplasion (a precancerous lesion). That’s why Barrett’s esophagus has a potential for developing esophageal adeno-carcinoma. Esophageal adeno-carcinoma is 80 times more common in people with Barrett’s esophagus than in others who have not been diagnosed with Barrett’s esophagus.
There is no treatment for Barrett’s esophagus. However, GERD can be treated, depending on the original cause, either with medicines (antacids, H2-blockers, proton pump-inhibitors…) or surgically.
Prevention of esophageal adeno-carcinoma can be done by performing a regular gastroscopy with a biopsy.