Testing the normal gastroesophageal junction.
D004935:Esophageal Diseases / Q000175:diagnosis*; D004943:Esophagogastric Junction / Q000502:physiology* / Q000503:physiopathology; D005764:Gastroesophageal Reflux / Q000175:diagnosis; D006548:Hernia, Diaphragmatic / Q000175:diagnosis; D006801:Humans; D006863:Hydrogen-Ion Concentration; D008365:Manometry