In Barrett’s esophagus, tissue in the tube connecting your mouth and stomach (esophagus) is replaced by tissue similar to the intestinal lining.
Barrett’s esophagus is often diagnosed in people who have long-term gastroesophageal reflux disease (GERD) — a chronic regurgitation of acid from the stomach into the lower esophagus. Only a small percentage of people with GERD will develop Barrett’s esophagus.
https://www.mayoclinic.org/diseases-conditions/barretts-esophagus/home/ovc-20322957?p=1
Barrett's esophagus