Achalasia is a swallowing disorder caused by loss of function in the esophageal body and the lower esophageal sphincter (the muscular ring at the junction of the esophagus and the stomach). Normally, when people swallow the esophageal body will sequentially contact and, the sphincter relaxes to allow food and liquid to pass into the stomach. With achalasia, the esophageal body do not contact and the sphincter does not relax, which causes food to be lodged in that area.