24-Hour pH Probe

The 24-hour pH probe (nasal catheter) evaluates the extent of acid reflux, or backflow, from the stomach into the esophagus. An esophageal motility test is first done to determine correct placement of the pH probe.

About the 24-Hour pH Probe Procedure
The following steps will occur during the procedure:

1. An esophageal motility test is first done to determine correct placement of the pH probe. This involves inserting a very small catheter into the nostril and advancing it into the stomach. The catheter is withdrawn slowly as you take sips of water. This portion of the test takes 20 to 25 minutes and the motility catheter is removed at the completion.

2. Next, a different catheter, called a pH probe, is inserted into the nostril and advanced into the esophagus. The pH probe will remain in place for 24 hours and is connected to a small recorder that you will carry on a strap over your shoulder. You will return the following day to have the probe removed. Written instructions will include information regarding diet, medications, smoking and bathing. You will also be provided a diary sheet to record selected events throughout the 24-hour period.

3. While the pH probe is in place, some patients experience irritation in the throat, which can be relieved by taking sips of water. Do not use throat lozenges, which could change the results of the test. Some patients report more difficulty sleeping than usual because of their awareness of the probe. Although the probe does not prevent eating or drinking, some patients find these activities somewhat uncomfortable. This discomfort lessens as you become adjusted to the probe being in place. 

Do not eat or drink anything after midnight prior to your test. Do not smoke the day of your test. Follow your physician’s instructions regarding discontinuing medications. Drugs such as proton pump inhibitors (Aciphex®, Prilosec®, Prevacid®, Protonix®, Nexium®) or H2 blockers (Axid®, Pepcid®, Tagamet®, Zantac®) may affect test results. It is recommended that these drugs be withheld seven days prior to the test. Your physician will instruct you whether to take these medications or withhold them. If your physician has instructed you to withhold the above medications and you are experiencing discomfort you may take antacids, such as Rolaids®, Tums® or Mylanta®. If you are an asthma patient bring your inhaler.

Some patients may experience a nosebleed. You may drive yourself home after the procedure.


Houston Methodist provides diagnostic testing, including the 24-hour pH probe procedure, at the following convenient locations.