Review article: intra-oesophageal impedance monitoring for the assessment of bolus transit and gastro-oesophageal reflux

Background Intra-oesophageal impedance monitoring can be used to assess the clearance of a swallowed bolus (oesophageal transit) and to detect gastro-oesophageal reflux independent of its acidity. Aim To discuss the clinical application of the impedance technique for the assessment of bolus transit and gastro-oesophageal reflux. Methods Review of the literature on intra-oesophageal impedance monitoring of bolus transit and gastro-oesophageal reflux. Results Using impedance criteria, normal oesophageal bolus clearance can be defined as complete clearance of at least 80% of liquid boluses and at least 70% of viscous boluses. Impedance recording identifies oesophageal function abnormalities in non-obstructive dysphagia patients and in patients with postfundoplication dysphagia. The impedance technique seems to be less suitable for the most severe end of the dysphagia spectrum like achalasia. Intra-oesophageal impedance monitoring detects reflux events independent of the pH of the refluxate, which allows identification of non-acid reflux episodes. In addition, use of impedance monitoring enables assessment of the composition (liquid, gas, mixed) and proximal extent of the refluxate. Combined impedance-pH monitoring is more accurate than pH alone for the detection of both acid and weakly acidic reflux. Furthermore, addition of impedance monitoring to pH increases the yield of symptom association analysis both in patients off and on proton pump inhibitor therapy. Conclusions Intra-oesophageal impedance monitoring is a feasible technique for the assessment of bolus transit and gastro-oesophageal reflux. Combined impedance-manometry provides clinically important information about oesophageal function abnormalities and combined impedance-pH monitoring identifies the relationship between symptoms and all types of reflux events regarding acidity and composition.