The Gastric Reflux Test (Multichannel Intraluminal Impedance Test) is performed to detect and record the number of times stomach contents come back into the esophagus and the relation of these episodes to symptoms (when a child cries, arches, coughs, gags, vomits, has chest pain, etc.). It also determines if the contents are acidic and how long they stay in the esophagus.

A thin light wire with an acid sensor as well as six to seven metal sensors is inserted through the nose into the lower part of the esophagus. The impedance probe is connected to a recorder box that the patient will carry with them for the duration of the study. Child life staff may be a useful resource to aid the patient and staff during placement of the probe, as this can be an uncomfortable procedure while awake.