Multichannel intraluminal impedance and pH monitoring in gastroesophageal reflux disease

The role of acid is very well established in the pathogenesis of gastroesophagea/reflux disease and acid suppression constitutes the main approach to its medical treatment. With the current frequent use of proton pump inhibitors, we are seeing increasing numbers of patients in whom symptoms persist despite pharmacological acid suppression. Reflux monitoring has been traditionally performed through esophageal pH measurement to detect acid reflux (i.e., drops in esophageal pH to below 4.0). Multichannel intraluminal impedance and pH measurement constitutes an important development in reflux monitoring because, in addition to detecting acid reflux, it enables measurement of nonacid reflux (i.e., with a pH > 4.0, also known as 'weakly acidic' for pH > 4 but < 7, or 'weakly alkaline' if pH > 7), which may be responsible for symptoms in some patients who are being treated with proton pump inhibitors. This review describes the approach to measuring nonacid reflux, the possible mechanisms responsible for symptoms due to this type of reflux, the clinical importance of this phenomenon and available treatment options; and the role of multichannel intraluminal impedance and pH monitoring in the evaluation of refractory gastroesophageal reflux disease.