pH Testing

For some patients with upper GI symptoms that are suggestive but not diagnostic for gastroesophageal reflux disease (GERD), testing the esophagus for acid reflux from the stomach can be helpful. When GERD is present, abnormal amounts of acid are passing up into the esophagus from the stomach causing inflammation and symptoms. To test for the presence as well as the frequency of acid reflux, a pH probe can be placed in the esophagus.

Prep Instructions

  • Do not eat or drink after midnight.

Additional Information

What is a pH monitor?

In the past, pH testing was done by passing a tube with an acid testing probe on the end of it through the nose and into the esophagus. The probe, or pH monitor, was then connected by flexible tubing to a recorder worn externally on a belt. This method was uncomfortable, interfered with daily activities and cumbersome to perform. Now, a pH probe about as big in diameter as a cocktail straw and only a half-inch long, can be placed into the esophagus during a regular upper endoscopy. Measurements from the probe are then transmitted by radiofrequency to an external recoding device the size of an older cell phone. Patients are asked to carry the device for 48 hours, and return it to the office. The probe inside is attached to the esophagus by a tiny pinch of tissue. After several days to a week it falls off, passes through the GI tract and then out in the stool and does not need to be recovered by the patient. Patients usually have no sensation of the probe and can swallow without difficulty.

What is the preparation for the pH testing?

The preparation for the endoscopy is no different than for a regular endoscopy. However, patients are usually asked to stop all acid suppressing medications for one week prior to the placement of the probe. Antacids such as TUMS, Gaviscon, or Mylanta can be taken during the week prior to the endoscopy.

What is the procedure to place a pH monitor?

Patients follow the instructions for preparation just as they would for an upper GI endoscopy. Once sedated, the upper GI endoscope is passed into the esophagus by way of the mouth. The examination of the upper GI tract is done just as it would be for an EGD. Then the doctor measures the distance from the front teeth to the end of the esophagus using the endoscope as a ruler. Immediately after removing the scope, the physician passes an even thinner catheter with the pH probe on the end of it. Once the esophagus is adequately deflated by applying gentle suction through the probe, the probe is placed using a pinch of tissue to stabilize it. The catheter is removed and the probe begins transmitting measurements of acidity to the recorder that the patient carries with them at all times for the next 48 hours. 

During those 48 hours, the patient is asked to keep a diary of when they eat, lie down, or feel any symptoms of GERD (coughing, regurgitation, or heartburn). At the end of the prescribed time, the patient will be instructed to bring the recorder and the diary back to the facility where the probe was placed. The data is then downloaded onto a computer, measured and analyzed.