AIM:To investigate differences in the physiopathological findings(manometry and pH monitoring) and symptoms between cases of non-erosive reflux disease(NERD) and erosive reflux disease(ERD) found positive at 24 h pH monitoring. METHODS:For a total of 670 patients who underwent 24 h pH monitoring,esophageal manometry and upper endoscopy were retrospectively evaluated,assessing the reflux symptoms,manometric characteristics of the lower esophageal sphincter(LES) and esophageal body and the presence or absence of esophagitis and hiatal hernia. Typical and atypical symptoms were also evaluated. For inclusion in the study,patients had to have NERD or ERD and be found positive on pH monitoring(NERD+) . Patients with Gastroesophageal reflux disease(GERD) complicated by stenosis,ulcers or Barrett’s esophagus were ruled out. RESULTS:214 patients were involved in the study,i.e. 107 cases of NERD+ and 107 of ERD. There were no significant gender-or age-related differences between the two groups. The ERD group had more cases of hiatal hernia(P = 0.02) and more acid reflux,both in terms of number of reflux episodes(P = 0.01) and as a percentage of the total time with a pH < 4(P = 0.00) ,when upright(P = 0.007) and supine(P = 0.00) . The NERD+ cases had more reflux episodes while upright(P = 0.02) and the ERD cases while supine(P = 0.01) . The LES pressure was higher in cases of NERD+(P = 0.03) while the amplitude and duration of their esophageal peristaltic waves tended to be better than in the ERD group(P >0.05) . The NERD+ patients presented more often with atypical symptoms(P = 0.01) . CONCLUSION:The NERD+ patients’ fewer reflux episodes and the fact that they occurred mainly while in the upright position(unlike the cases of ERD) may be two factors that do not favor the onset of esophagitis. The frequently atypical symptoms seen in patients with NERD+ need to be accurately evaluated for therapeutic purposes because patients with GERD and atypical symptoms generally respond only partially to medical and surgical treatments. AIM: To investigate differences in the physiopathological findings (manometry and pH monitoring) and symptoms between cases of non-erosive reflux disease (NERD) and erosive reflux disease (ERD) found positive at 24 h pH monitoring. METHODS: For a total of 670 patients who underwent 24 h pH monitoring, esophageal manometry and upper endoscopy were retrospectively evaluated, assessing the reflux symptoms, manometric characteristics of the lower esophageal sphincter (LES) and esophageal body and the presence or absence of esophagitis and hiatal hernia. Typical and atypical symptoms For inclusion in the study, patients had to have NERD or ERD and be found positive on pH monitoring (NERD +). Patients with Gastroesophageal reflux disease (GERD) complicated by stenosis, ulcers or Barrett’s esophagus were ruled out. RESULTS: 214 patients were involved in the study, ie 107 cases of NERD + and 107 of ERD. There were no significant gender-or age-related differences between the two groups. The ERD group had more cases of hiatal hernia (P = 0.02) and more acid reflux, both in terms of number of reflux episodes (P = 0.01) and as a percentage of the total time with pH <4 (P = 0.00) , when upright (P = 0.007) and supine (P = 0.00). The NERD + cases had more reflux episodes while upright (P = 0.02) and the ERD cases while supine (P = 0.01) NERD + (P = 0.03) while the amplitude and duration of their esophageal peristaltic waves tended to be better than in the ERD group (P> 0.05). The NERD + patients presented more often with atypical symptoms (P = 0.01). CONCLUSION: The NERD + patients’ fewer reflux episodes and the fact that they occurred mainly in the upright position (unlike the cases of ERD) may be two factors that do not favor the onset of esophagitis. The frequently atypical symptoms seen in patients with NERD + need to be accurately evaluated for therapeutic purposes because patients with GERD and atypical symptoms generally respond only partially to medical and surgical treatments.