Inclusion Criteria:  A- Treated achalasia patients with gastroesophageal reflux symptoms  Diagnosis of idiopathic achalasia confirmed by oesophageal manometry that shows the following criteria: Aperistalsis or simultaneous contractions in the oesophageal body. Impaired relaxation of the Lower oesophageal sphincter Treatment of achalasia with per-oral endoscopic myotomy (POEM) The minimum total score on the Gastroesophageal Reflux Disease Questionnaire (GERDQ) of ≥ 8. Gastroesophageal symptoms after treatment lasting more than three months. Age 18-80 years. Written informed consent.  B- Treated achalasia patients without gastroesophageal reflux symptoms  Diagnosis of idiopathic achalasia confirmed by oesophagal manometry that shows the following criteria:  Aperistalsis or simultaneous contractions in the oesophageal body. Impaired relaxation of the Lower oesophageal sphincter Treatment of achalasia with per-oral endoscopic myotomy (POEM) The maximum total score on the Gastroesophageal Reflux Disease Questionnaire (GERDQ) of < 8. Age 18-80 years. Written informed consent.  EXCLUSION CRITERIA-  Pseudoachalasia. Upper gastrointestinal malignancy. Chagas disease. Peptic ulcer disease. Inability to stop PPI, H2-receptor antagonist or prokinetic drug for two weeks Presence of an extremely dilated oesophagus body >5 cm