In gastroesopahgeal reflux, stomach contents wash up into the esophagus, causing irritation and indigestion. Over time, GERD can lead to Barrett esophagus, in which intestinal lining replaces the normal lining of the esophagus. People with Barrett esophagus are at increased risk for cancer of the esophagus. The chances of cancer are greatest in patients with Barrett esophagus and dysplasia, a precancerous abnormality of the lining of the esophagus. To diagnose Barrett esophagus, doctors insert a tube with a small camera on the end through patients' mouths into the esophagus, a procedure called endoscopy. Some have proposed that patients with GERD should have endoscopy to screen for Barrett esophagus. Patients with Barrett esophagus would then have periodic endoscopy to find tumors when they are small and treatable. Since reflux is very common, this screening strategy could affect many people and be expensive.