An x-ray study of the portion of the digestive canal between the throat and stomach (esophagus) in which the patient swallows a barium mixture while the radiologist watches for signs of narrowing, irregularity or blockage. No preparation is required except fasting. Sometimes, in a procedure called an upper gastrointestinal (UGI) series, the barium is also observed after it enters the stomach to check for stomach problems or ulcers.
