4. MATERIALS AND METHODS High Resolution Manometry Esophageal body pressure, peristalsis and pressure of the lower esophageal sphincter (LES) and the upper part of the stomach will be measured using HRM, as it is routinely performed in the university hospital of Gasthuisberg in patients with symptoms of dysphagia. HRM consists of measuring multiple pressures simultaneously and this allows detailed assessment of all relevant data for the entire esophagus.