Esophageal pH monitoring is a test that measures how often and for how long stomach acid enters the tube that leads from the mouth to the stomach (esophagus).

A thin tube is passed through your nose or mouth to your stomach. Then it is pulled back into your esophagus. The tube is attached to a monitor that measures the level of acidity in your esophagus.

You will wear this monitor on a strap and will be asked to keep a diary of your symptoms and activity over the next 24 hours. The next day you will return and the tube will be removed. The information from the monitor will be compared with the diary notes you provide.

Infants and children will most likely remain in the hospital for the esophageal pH monitoring.

Your health care provider will ask you to not eat or drink (fast) and avoid smoking after midnight before the test.

Some drugs may change the test results. Your health care provider may ask you to not take those drugs for 24 hours to 2 weeks (or more) before the test, depending on the medication. These substances may include:

• Adrenergic blockers
• Alcohol
• Antacids
• Anticholinergics
• Cholinergics
• Corticosteroids
• H2 blockers
• Proton pump inhibitors

Do not stop taking any medication unless told to do so by your health care provider.

You may experience a brief gagging sensation as the tube is passed through your throat.

Esophageal pH monitoring is used to check how much stomach acid is entering the esophagus, and how well it is cleared downward into the stomach. It is a test for gastroesophageal reflux disease (GERD).

This test can also be performed during upper GI endoscopy by clipping a pH monitoring device to the lining of the esophagus. In infants, this test is also used to check for GERD and related excessive crying or other problems.

Normal value ranges may vary slightly among different laboratories. Talk to your doctor about the meaning of your specific test results.

Increased acid in the esophagus may be a sign of:

• Barrett's esophagus
• Difficulty swallowing (dysphagia)
• Esophageal scarring
• Gastroesophageal reflux disease (GERD)
• Heartburn
• Reflux esophagitis

If you have esophagitis, you may need these additional tests:

• Barium swallow
• Esophagogastroduodenoscopy (also called upper GI endoscopy)

No significant risks have been reported with this test, but the following may occur rarely:

• Arrhythmias during insertion of the tube
• Breathing in of vomit if the catheter causes vomiting (see aspiration of vomitus)

Orlando RC. Diseases of the esophagus. In: Goldman L, Ausiello D, eds. Cecil Medicine. 23rd ed. Philadelphia, Pa: Saunders Elsevier; 2007: chap 140.