Esophageal pH Monitoring

Gastroesophageal reflux disease (GERD) is a common disorder of the gastrointestinal tract that involves the movement of stomach contents into the esophagus or mouth, causing discomfort or complications.[1] Population-based studies have identified GERD as one of the most common upper gastrointestinal (GI) tract disorders, with a prevalence of about 20% in the United States.[2] Patients may present with typical symptoms, including heartburn or regurgitation, or atypical symptoms such as cough, asthma, hoarseness, chronic laryngitis, throat-clearing, chest pain, dyspepsia, and nausea.[3] Typically, GERD is diagnosed clinically and with the response to a trial of proton-pump inhibitor (PPI) therapy. Relief of heartburn and regurgitation after a 6 to 8 week trial of PPI therapy is a reliable indicator of GERD. This approach has a sensitivity of 78% and a specificity of 54%; hence a negative trial does not rule-out GERD.[4] However, this is a cost-effective approach to diagnosing GERD rather than proceeding directly to endoscopic or alternative diagnostic testing.[5] If patients present with alarm features (i.e., new-onset dyspepsia at age greater than 60, GI bleeding, dysphagia, odynophagia, weight loss, anemia, persistent vomiting), a trial of PPI therapy is not necessary and the work-up should directly proceed to early endoscopy.[3] Ambulatory esophageal pH testing is done with a wireless pH capsule or a traditional pH probe and is the gold standard test for the diagnosis of GERD.[3] There are some patients with typical or atypical GERD symptoms that have a normal upper endoscopy and normal ambulatory esophageal pH testing but are unresponsive to standard PPI therapy. Ambulatory pH testing does not detect all types of reflux, especially when the refluxate contains little or no acid.[6] It relies on the acidification of intraesophageal pH to less than 4 as a marker for the presence of gastric contents in the esophagus to diagnose gastroesophageal reflux (GER) episodes. Hence, it has limited use in detecting episodes where the pH fails to fall below 4.[7] A newer technique combining multichannel intraluminal impedance (MII) testing with pH testing, allows for the detailed characterization of the refluxate, including its physical and chemical properties.[2] The MII detects the intraluminal bolus movement with the esophagus via strategic placement of a catheter, and it can characterize, in combination with pH testing, whether the bolus is composed of liquid, gas, or mixed components as well as its pH.[2]