The esophagus is the muscular tube that carries food and liquid from the throat to the stomach. However, it is not a rigid tube. The muscles in the wall of the esophagus automatically contract when a person swallows. This type of contraction, called peristalsis, occurs as a sweeping wave down the esophagus. It literally squeezes the food or liquid along from the mouth to the stomach.
Another important part of the esophagus is the Lower Esophageal Sphincter (LES). It is a strong muscular ring located where the esophagus enters the stomach. This specialized muscle remains tightly closed most of the time. It is supposed to open only to allow food and liquid to enter the stomach. Occasionally, the LES opens at the wrong time, allowing caustic stomach acid and bile to splash up into the esophagus. This is called acid reflux. It is reflux that is responsible for the discomfort of heartburn. Almost everyone has experienced heartburn occasionally, and it is usually nothing to be concerned about. However, when it happens on a regular basis, it can lead to damage and scarring in the esophagus.
pH is a measure of acidity or alkalinity. Most people are familiar with pH tests done on soil or swimming pools. An esophageal pH test measures how often stomach acid flows into the lower esophagus and the degree of acidity during a 12 to 24 hour period.
The equipment used for an esophageal pH test consists of a small, thin probe to measure acidity, fixed at the end of flexible tubing. The other end of the tubing is attached to a portable recorder that is carried at the waist. The probe and tubing is gently inserted through the nose and down to the end of the esophagus. Over 12 to 24 hours, the acidity in the lower esophagus is recorded on a paper tape. When the patient experiences reflux or other symptoms, he / she presses a button on the recorder to mark the time of the occurrence. This then allows a comparison of particular readings to be made in relationship to normal acidity readings. The recording of the full time period is then analyzed, and a full report is sent back to the physician.
Reasons for the Exam
There are several normal mechanisms that keep acid out of the esophagus. The first is swallowed saliva which helps neutralize stomach acid. Second are the sweeping muscle contractions that act to cleanse the lower esophagus of acid reflux. Third is the protective contraction of the LES. When any of these protective processes are not working properly, acid reflux may occur and cause symptoms. There are a number of symptoms that originate in the esophagus, including heartburn, difficulty swallowing food or liquid, and chest pain. A measurement of esophageal pH is of great importance in evaluating these symptoms and allowing the physician to treat problems of acid reflux. Pre- and post-treatment measurement of pH may be helpful in determining the success of treatment for acid reflux.
X-ray examination (known as upper GI series or barium swallow), and endoscopy are other diagnostic tests often used when these symptoms are present in the esophagus.
The preparation for an esophageal pH measurement is simple and straightforward. The patient should consume no food or liquid for about 8 hours before the test begins. In most cases, the physician will want to study the esophagus in its natural state, without the effects of any medication which might alter its function.
Patients should review all medications they are taking with their physicians, so they can be advised which medications they should and discontinue before the test. Generally, the following list of drugs may affect how much acid flows into the esophagus. They usually need to be discontinued at least 48 hours before the test begins. Patients should not discontinue taking any medication without consulting their physician.
Caffeine (coffee, tea, cola, chocolate)
Reglan (generic: metoclopramide)
Urecholine (generic: bethanechol)
Erythromycin (E-Mycin, and others)
Nitroglycerin (Isordil, and others)
Calcium channel blockers (Procardia, Adalat, Calan, Cardizem, and others)
Beta blockers (Corgard, Inderal, Lopressor, and others)
Tagamet (generic: cimetidine)
Zantac (generic: ranitidine)
The measurement of esophageal pH begins with the process of inserting and connecting the pH probe, which takes approximately 10 to 15 minutes. While the patient is comfortably seated or lying on his / her side, a thin soft piece of tubing is gently passed through the nose, or occasionally through the mouth. Upon swallowing, the tip of the tube enters the esophagus and the medical technician or nurse then quickly passes it down to the desired level. There is usually some slight gagging at this point, but it is easily controlled by following instructions. The tubing is then attached to the waist recorder, and the patient is sent on to his or her regular daily activities.
The esophageal pH test records the level of acidity escaping the stomach over a period of time. These measurements are then analyzed and compared to normal levels of acidity. It is typical for the test to show a small amount of acid seeping into the esophagus at various times during the day and night. This minor occurrence of acid is normal for almost everyone, and most people may not even be aware of symptoms. However, if the protective actions of the esophagus do not function properly, the test will show a greater degree and duration of stomach acid in the esophagus. .After the measurement results have been analyzed, the physician will explain the results to the patient and recommend treatment.
The primary benefit of the exam is that the physician has clear documentation of the degree and duration of acidity in the esophagus. With this information, a specific treatment program can be outlined, or reassurance can be provided if the exam results are normal.
While there are other examinations used to study the esophagus, such as upper GI series and endoscopy, nothing really takes the place of esophageal pH measurement in the diagnosis and treatment planning for acid reflux. Esophageal pH is often done in association with a pressure recording of the esophagus, known as Esophageal Manometry.
Side Effects and Risks
Generally there are no serious problems associated with the esophageal ph test. Once the tube is in place, it is usually easily tolerated.
Esophageal pH is a valuable method of determining the severity of acid reflux into the esophagus. With this information, the physician can usually develop effective treatment for most patients who have acid disorders in the lower esophagus.