Epithelial Damage in GERD

Inclusion Criteria: * Typical GERD-symptoms lasting for more than 6 months (recurrent episodes of heartburn or acid regurgitation) * abnormal pH-parameters (pathological acid exposure and/or symptom association) Exclusion Criteria: * Age \<18 years * Previous esophageal or gastric surgery * Severe esophageal motility disorder on manometry * Histological evidence of Barrett's mucosa * Severe co-morbidities (including cardiopulmonary disease, portal hypertension, collagen diseases, morbid obesity, coagulation disorders and co-morbidity hindering a gastroscopic procedure) * Use of anticoagulant or immunosuppressive drugs * Inability to stop medication that can influence the test results, like PPI, for at least 10 days before tests * Excessive alcohol consumption (\>20 units per week) * Patients unable to give informed consent.