In patients with persistent reflux symptoms despite PPI therapy and normal findings on endoscopy a fur- ther evaluation is recommended in order to establish the diagnosis of GERD or to identify alternative diagnoses, as esophageal abnormalities achalasia), functional heartburn, or eosinophilic esophagitis. Thus, manometry should be the second diagnostic test in order to evaluate peristaltic function and diagnose achalasia. This test helps to analyze the function of the peristaltic activity of the body of the esophagus and the LES, prior to anti- reflux surgery. Normal pressures at the LES range between 12 and 30 mmHg. A mechanically defective sphincter is defined as having one of the following characteristics: an average resting pressure of less than 6 g, an average length of less than 2 cm or an average length exposed to the positive