title: Review article: The measurement of non-acid gastro-oesophageal reflux.
abstract: BACKGROUND
  Oesophageal pH monitoring has been used for three decades to study gastro-oesophageal reflux, but it does not allow detection of non-acid reflux episodes.
  
  
  OBJECTIVE
  To discuss the techniques by which non-acid reflux can be measured and to evaluate the clinical relevance of such measurements.
  
  
  METHODS
  Review of the literature on non-acid reflux monitoring.
  
  
  RESULTS
  Ambulatory oesophageal impedance monitoring (using a catheter with ring electrodes) allows one to detect all types of gastro-oesophageal reflux, acid as well as non-acid. Measurement of intra-oesophageal bilirubin concentration also detects reflux irrespective of the pH, but only when there is bilirubin in the gastric juice and technical short-comings limit the applicability of this technique. In untreated subjects, about 50% of reflux episodes are non-acid (nadir pH > 4). In patients on acid inhibition, up to 95% of reflux episodes are non-acid. Treatment with an acid inhibitor leads to a significant decrease in the incidence of acid reflux episodes, but not to a reduction in the total number of reflux episodes. This shift is associated with a shift in symptoms from heartburn to regurgitation. With impedance monitoring, the temporal association between symptoms that persist during inhibition of acid secretion and non-acid reflux events can be demonstrated. In a proportion of patients with chronic cough, the coughing episodes are preceded by non-acid reflux.
  
  
  CONCLUSIONS
  Intraluminal impedance monitoring of gastro-oesophageal reflux is a feasible technique, which provides clinically important information about the relationships between symptoms and non-acid reflux events.
authors: Department of Gastroenterology, University Medical Center Utrecht, Utrecht, The Netherlands. asmout@umcutrecht.nl
authors: A J P M
authors: AJ
authors: Smout
mesh_terms: D001663:Bilirubin / Q000378:metabolism*; D003371:Cough / Q000209:etiology*; D050782:Esophageal pH Monitoring / Q000295:instrumentation*; D005764:Gastroesophageal Reflux / Q000150:complications / Q000188:drug therapy*; D006801:Humans; D018670:Monitoring, Ambulatory / Q000379:methods
chemical_list: D001663:Bilirubin