Gastro-esophageal reflux disease (GERD) is defined as the reflux of gastric content into the esophagus that causes troublesome symptoms or complications. Nine to 30% of the population suffers from GERD-suggestive symptoms (heartburn, regurgitation, chest pain, chronic couch, sore throat). In the absence of warning signs, proton pump inhibitors (PPI) are prescribed as first-line treatment. However, 20 to 60% of patients are unsatisfied because of persistent symptoms when taking PPI. Causes of persistent symptoms are: erroneous diagnosis of GERD (up to 50% of PPI non-responders), rumination syndrome, excessive weakly acid reflux on PPI due to defective esophago-gastric junction or an excessive number of transient lower esophageal sphincter relaxations (main mechanism of GERD), poor acid secretion inhibition on PPI, and non-compliance to therapy. Complementary examinations are indicated to explain persistent GERD symptoms. Upper gastro-intestinal endoscopy is performed first to rule out an esophageal tumor and to identify erosive esophagitis, a specific sign of GERD. However, it is normal in up to 70% of symptomatic GERD patients. Direct detection of reflux episodes is then requested to confirm GERD. The gold standard for reflux detection is the ambulatory measurement of esophageal pH for 24 to 96 hours using a catheter (catheter-based pH-monitoring) or a capsule clipped into the esophagus (wireless pH-monitoring). Reflux episodes are defined as an esophageal pH \< 4. Another method of reflux detection is based on liquid and gas detection in the esophagus using pH-impedance monitoring. Recently the combination of impedance and esophageal pressure monitoring, called esophageal high resolution impedance manometry (HRIM) was introduced to simultaneously identify reflux episodes and their mechanisms. It has several advantages over esophageal pH measurement: shorter recording duration (1 or 2 hours post prandial) and identification of reflux mechanisms that might guide the choice of the best therapeutic option. Hypothesis: The 1-hour post prandial esophageal HRIM might be useful to diagnose GERD.