['Duodenogastroesophageal reflux (DGER) can greatly increase microscopic and macroscopic esophageal mucosal damage caused by acid. The aim of this study was simultaneously to assess the chemical composition of DGER by detecting bilirubin in the refluxate by means of Bilitec and describe its pH and physical properties by impedance monitoring, in order to prove that non-acid reflux and biliary reflux are two distinct phenomena.', 'Twenty patients with gastroesophageal reflux disease (GERD) with symptoms refractory to conventional proton-pump inhibitor (PPI) therapy or with atypical GERD symptoms were included in the study. All patients underwent upper gastrointestinal endoscopy and simultaneous Bilitec and intraeosophageal impedance (IIM) and pH monitoring. In the majority of patients (16/20), the tests were performed while assuming a standard PPI dose.', 'Pathological bilirubin exposure, as defined by intraesophageal bilirubin absorbance above 0.14 for more than 3.9% of the time, was present in 9 cases, 6 of them with normal values of non-acid reflux, as detected by IIM. A pathological non-acid reflux, as defined by an IIM showing a percentage time with non-acid reflux greater than 1.4%, was observed in 5 patients, 2 of whom had no pathological biliary reflux, as detected by Bilitec. No correlation was found between the two indices, as expressed by an r-value of -0.12 (p>0.05).'] Are biliary reflux and non-acid reflux two distinct phenomena : a comparison between 24-hour multichannel intraesophageal impedance and bilirubin monitoring?