Acid reflux disease can often be diagnosed by symptoms alone, but there are also more sophisticated ways to make the diagnosis. These diagnostic tests can be divided into three basic categories: endoscopy, radiology and pH monitoring.
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Endoscopy is a minimally invasive way to examine the inside of the body using a very small camera that is embedded within a long, thin instrument called an endoscope. The endoscope is introduced into the body through a natural body opening, such as the mouth or nose. The most commonly performed test to diagnose gastroesophageal reflux disease (GERD) involves the use an endoscope to examine the structures that may be injured by acid damage.
Upper endoscopy — also known as esophagogastroduodenoscopy or EGD — is performed by placing an endoscope past the mouth, then advancing it through the throat and down the esophagus into stomach, with it eventually entering the upper part of the small intestine, known as the duodenum. Although EGD is a relatively painless procedure, a powerful gag reflex occurs when the endoscope touches the back of the tongue or throat. Because of this, people generally require sedating medications when they undergo EGD.
Transnasal esophagoscopy, or TNE, is another endoscopy technique that can be used to diagnose GERD as well as laryngopharyngeal reflux disease (LPRD). With TNE, a very small camera is embedded into an ultrathin instrument about the width of a piece of spaghetti. This instrument is inserted through the nose to examine the throat, esophagus and top of the stomach. TNE does not require sedation because the gag reflex is minimal when going through the nose with such a thin instrument.
During both EGD and TNE, small tissue samples can be obtained from the areas being visualized. These biopsies are then examined under a microscope by a pathologist to help make the diagnosis of acid reflux disease as well as to rule out the possibility of other conditions, such as cancer.
There are two X-ray tests that can be used to investigate acid reflux disease: a barium swallow or an upper gastrointestinal, or GI, series. With both of these exams, the individual drinks a thick barium-containing white liquid, and X-rays are taken during and immediately after swallowing to follow the path of barium. During a barium swallow — also called an esophagram — the barium is visualized as it travels through the esophagus from the throat to the stomach. During an upper GI series, the barium is followed through the esophagus and stomach to the small intestine.
While these X-ray studies will help diagnose GERD if barium is seen refluxing from the stomach into the esophagus, people with GERD do not have reflux all of the time. Therefore, reflux may not be observed during the studies. However, these tests can provide other important information, such as whether there are blockages or areas of narrowing in the esophagus, which may be due to GERD or other conditions.
Esophageal pH and Impedance Monitoring
Testing pH levels is the only way to directly determine whether acid is being refluxed into the esophagus. There are two techniques available: a catheter-based esophageal pH monitoring system and a wireless technique. The catheter-based technique is a 24-hour test in which a catheter is placed via the nose into the lower part of the esophagus. One end of the catheter stays in the esophagus and the other end stays outside the nose, where it is attached by a thin wire to a small recording device for 24 hours. For this 24-hour period, the individual keeps a diary of meals and symptoms while the device continuously measures pH levels in the esophagus.
The wireless technique involves a 48-hour recording of esophageal acid exposure. A tiny acid-sensing capsule is inserted during endoscopy and clipped into place in the lower portion of the esophagus. Measurements are then transmitted to a small recording device worn around the waist. The advantages of the wireless system are that it is more comfortable, and because there is no catheter coming out of the nose, it is easier for the person to go about his routine activities. Furthermore, it gives a longer and more accurate representation of esophageal acid exposure.
While catheter-based systems have the drawbacks of being somewhat uncomfortable and affecting the person’s appearance, they have the advantage of allowing impedance testing to be performed at the same time as pH testing. Impedance systems have both pH and impedance sensors on the catheter, which allow the detection of not only acid reflux from the stomach, but also the reflux of nonacid substances, such as bile acid from the duodenum. Although less common than acid reflux, bile acid reflux can also produce GERD, with inflammation of the esophagus.
Because impedance-pH monitoring has the ability to detect reflux of different types of substances, it is more accurate than pH testing alone for detecting gastroesophageal reflux. It is an ideal test for someone who is still having symptoms despite being on medications for acid reflux disease. These individuals often have episodes of only weakly acidic reflux, which are best detected by the pH-impedance method.
Pharyngeal pH Monitoring
In much the same way that esophageal pH monitoring can be used to assess esophageal acid exposure, pH monitoring can also be utilized to detect the presence of acid in the pharynx, or throat. Pharyngeal pH monitoring is a catheter-based system in which a thin wire with pH sensors is placed via the nose into the throat, and over a 24-hour period pH levels are recorded and transmitted to a recording device worn around the waist. Pharyngeal pH monitoring is used to diagnose LPRD, although there is some controversy among experts about what is considered an abnormal number of acid reflux episodes in the throat.