Barrett's oesophagus. Endoscopic view of the inside of a patient's oesophagus, showing damage (white areas) caused by Barrett's oesophagus. Barrett's is a condition in which the epithelial cells at the lower part of the oesophagus (gullet) change, a process called metaplasia. It is caused by chronic acid reflux, where stomach acids escape from the stomach into the oesophagus. This causes heartburn. Over time, the normal squamous cells found in the oesophagus are replaced by columnar cells, similar to those that line the stomach or colon. The condition is considered a precursor of oesophageal cancer. Treatment is with drugs to reduce stomach acid production, although advanced cases may require surgery or cancer treatments.