Multichannel intraluminal impedance in esophageal function testing and gastroesophageal reflux monitoring.

Multichannel intraluminal impedance (MII) is a new technique for evaluating esophageal function and gastroesophageal reflux. This technique depends on changes in resistance to alternating current between two metal electrodes produced by the presence of bolus inside the esophageal lumen. Combined MII and manometry (MII-EM) provides simultaneous information on intraluminal pressure changes and bolus movement, whereas combined MII and pH (MII-pH) allows detection of pH episodes irrespective of their pH values (ie, acid and non-acid reflux). Combined MII-EM studies are performed very similarly to standard manometry. Based on studies in healthy volunteers and patients, combined MII-EM challenges current existing criteria that define the effectiveness of esophageal body function. Combined MII-pH testing brings a shift in gastroesophageal reflux testing paradigm. In MII-pH studies, reflux events are no longer detected by pH. Refluxate presence, distribution, and clearing are primarily detected by MII and simply characterized as acid versus non-acid based on pH change and as liquid, gas, or mixed based on MII. MII determines refluxate clearance time, whereas pH measures acid clearance time. MII-pH shows promise to become an important clinical tool, particularly to assess gastroesophageal reflux in the postprandial period and in patients with persistent symptoms on therapy and with atypical symptoms.