Esophageal multichannel intraluminal impedance testing
- Radu Tutuian, MD
Radu Tutuian, MD
- Associate Professor, Gastroenterology
- University of Bern, Switzerland
- Donald O Castell, MD
Donald O Castell, MD
- AGA Peer Reviewer
- Professor of Medicine
- Director, Esophageal Disorders Program
- Medical University of South Carolina
Multichannel intraluminal impedance (MII) is a catheter-based method to detect intraluminal bolus movement within the esophagus. MII is performed in combination with manometry or pH testing. When combined with manometry, it provides information on the functional (ie, bolus transit) component of manometrically detected contractions. When combined with pH testing, it allows for the detection of gastroesophageal reflux independent of pH (ie, both acid and non-acid reflux).
This topic will review the principles, technique, and results of esophageal MII testing, and their clinical implications. Motility testing and high-resolution esophageal manometry are discussed in detail, separately. (See "High resolution manometry" and "Overview of gastrointestinal motility testing" and "Esophageal motility disorders: Clinical manifestations, diagnosis, and management".)
PRINCIPLES OF IMPEDANCE TESTING
Impedance testing is based on the measurement of changes in resistance to alternating electrical current when a bolus passes by a pair of metallic rings mounted on a catheter. In an empty tubular organ such as the esophagus, the electrical current between the two rings is conducted by the few ions present in and on the mucosa. Liquid-containing boluses with an increased number of ions have a higher conductivity and, when entering the impedance-measuring segment, will lower the impedance to a nadir value. The impedance stays at its nadir as long as the bolus is present in the segment, returning to baseline once the bolus is cleared by a contraction. The contraction produces a slight increase in impedance above the baseline due to a decrease in luminal cross-section. Gas passing transiently by the impedance-measuring segments will produce a rapid and high (usually >3000 Ohms) rise in the impedance since it has poor electrical conductance.
Measuring impedance at multiple sites (multichannel) allows for determination of the direction of bolus movement based upon temporal differences in bolus entry and exit. Bolus entries progressing from proximal to distal indicate antegrade bolus movement, while bolus entries progressing from distal to proximal indicate retrograde bolus movement (waveform 1).
COMBINED MULTICHANNEL INTRALUMINAL IMPEDANCE AND MANOMETRY
Standard manometry does not demonstrate whether a contraction results in actual bolus passage. Combined multichannel intraluminal impedance with esophageal manometry (MII-EM) is a test of esophageal function as it provides information about both pressures and bolus transit within the esophagus.
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- PRINCIPLES OF IMPEDANCE TESTING
- COMBINED MULTICHANNEL INTRALUMINAL IMPEDANCE AND MANOMETRY
- Patient protocol
- Impedance results parameters
- Clinical application
- COMBINED MULTICHANNEL INTRALUMINAL IMPEDANCE AND PH
- Patient protocol
- - Testing on or off proton pump inhibitors
- Impedance-pH results parameters
- - Refluxate composition
- - Proximal extent of reflux
- - Number of acid and non-acid reflux episodes
- - Refluxate contact time
- - Refluxate clearance time
- - Reflux pH
- Interpretation of results
- - Reference values
- - Symptom correlation measures
- Clinical application
- COMPLICATIONS AND CONTRAINDICATIONS
- SUMMARY AND RECOMMENDATIONS