The esophagus is the muscular tube that carries food, and liquids from your mouth to the stomach. You may not be aware of your esophagus until you swallow something too large, too hot, or too cold. You may also notice it when something is wrong. You may feel pain or have trouble swallowing. The most common problem with the esophagusis GERD (gastro esophageal reflux disease). With GERD, a muscle at the end of your esophagus does not close properly. This allows stomach contents to leak back, or reflux, into the esophagus and irritate it. Over time, GERD can cause damage to the esophagus. Other problems include heartburn, cancer, and esophagitis. Doctors may use various tests to make a diagnosis. These include imaging tests, an upper endoscopy, and a biopsy.