The objective of this study is to design and use a novel, minimally invasive mucosal impedance (MI) technology to inexpensively and accurately test mucosal health in suspected gastroesophageal reflux disease (GERD) and nonerosive reflux disease (NERD) patients as compared to those without GERD.

During routine esophagogastroduodenoscopy (EGD), consented study participants will have the original single channel MI catheter advanced through the working channel of the endoscope. Measurements will be taken at 3 locations for 5 seconds each. The catheter will then be removed and a custom-designed balloon assembly will be inserted through the working channel of the endoscope. The balloon assembly will expand to a maximum diameter of 2 cm spanning from the distal to mid esophagus and contain external metal contacts to form 40 impedance channels made up by 10 axial channels spanning a 10 cm axial area and four radial channels.This design will allow us to measure mucosal impedance both axially and radially thus enabling us to assess the discriminating ability of the device for reflux disease. The balloon assembly will be held in place for 5 seconds. Once the mucosal impedance data have been recorded, the balloon assembly will be deflated and removed by the investigator. The study procedure will add approximately 1-3 minutes of procedure time for each research participant.

Those participants who are diagnosed with Grade C or D esophagitis at the initial visit will return for a follow-up visit after treatment with proton pump inhibitor (PPI) therapy to determine whether or not esophagitis has healed as part of their standard of care. If no esophagitis is detected at the follow-up EGD, we will gather one final comparison MI reading during this visit. If esophagitis is still present, follow-up MI will not be performed.

Inclusion Criteria:

• Patients who are undergoing standard of care EGD with or without BRAVO pH capsule placement

Exclusion Criteria:

• Age less than 18 years old
• Patients unable to give informed consent
• Use of acid suppressive therapy within last 10 days
• Known history of Barrett's esophagus or gastric surgery, other than non-functioning (slipped) Nissen fundoplication

Patients who are scheduled for endoscopic procedures (esophagogastroduodenoscopy (EGD)) by the principal investigator as part of their routine care and who do not meet any of the pre-defined exclusion criteria will be considered for participation in the study.