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- Symptoms and procedures to diagnose GERD
- GERD (acid reflux) tests
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Quick GuideHeartburn: Causes, Symptoms, Remedies, Treatments
GERD (acid reflux) tests
Esophageal acid testing
Esophageal acid testing is considered a "gold standard" for diagnosing GERD. As discussed previously, the reflux of acid is common in the general population. However, patients with the symptoms or complications of GERD have reflux of more acid than individuals without the symptoms or complications of GERD. Moreover, normal individuals and patients with GERD can be distinguished moderately well from each other by the amount of time that the esophagus contains acid.
The amount of time that the esophagus contains acid is determined by a test called a 24-hour esophageal pH test. (pH is a mathematical way of expressing the amount of acidity.) For this test, a small tube (catheter) is passed through the nose and positioned in the esophagus. On the tip of the catheter is a sensor that senses acid. The other end of the catheter exits from the nose, wraps back over the ear, and travels down to the waist, where it is attached to a recorder. Each time acid refluxes back into the esophagus from the stomach, it stimulates the sensor and the recorder records the episode of reflux. After a 20 to 24 hour period of time, the catheter is removed and the record of reflux from the recorder is analyzed.
There are problems with using pH testing for diagnosing GERD. Despite the fact that normal individuals and patients with GERD can be separated fairly well on the basis of pH studies, the separation is not perfect. Therefore, some patients with GERD will have normal amounts of acid reflux and some patients without GERD will have abnormal amounts of acid reflux. It requires something other than the pH test to confirm the presence of GERD, for example, typical symptoms, response to treatment, or the presence of complications of GERD. GERD also may be confidently diagnosed when episodes of heartburn correlate with acid reflux as shown by acid testing.
pH testing has uses in the management of GERD other than just diagnosing GERD. For example, the test can help determine why GERD symptoms do not respond to treatment. Perhaps 10 to 20 percent of patients will not have their symptoms substantially improved by treatment for GERD. This lack of response to treatment could be caused by ineffective treatment. This means that the medication is not adequately suppressing the production of acid by the stomach and is not reducing acid reflux. Alternatively, the lack of response can be explained by an incorrect diagnosis of GERD. In both of these situations, the pH test can be very useful. If testing reveals substantial reflux of acid while medication is continued, then the treatment is ineffective and will need to be changed. If testing reveals good acid suppression with minimal reflux of acid, the diagnosis of GERD is likely to be wrong and other causes for the symptoms need to be sought.
pH testing also can be used to help evaluate whether reflux is the cause of symptoms (usually heartburn). To make this evaluation, while the 24-hour ph testing is being done, patients record each time they have symptoms. Then, when the test is being analyzed, it can be determined whether or not acid reflux occurred at the time of the symptoms. If reflux did occur at the same time as the symptoms, then reflux is likely to be the cause of the symptoms. If there was no reflux at the time of symptoms, then reflux is unlikely to be the cause of the symptoms.
Lastly, pH testing can be used to evaluate patients prior to endoscopic or surgical treatment for GERD. As discussed above, some 20% of patients will have a decrease in their symptoms even though they don't have GERD (the placebo effect). Prior to endoscopic or surgical treatment, it is important to identify these patients because they are not likely to benefit from the treatments. The pH study can be used to identify these patients because they will have normal amounts of acid reflux.
A newer method for prolonged measurement (48 hours) of acid exposure in the esophagus utilizes a small, wireless capsule that is attached to the esophagus just above the LES. The capsule is passed to the lower esophagus by a tube inserted through either the mouth or the nose. After the capsule is attached to the esophagus, the tube is removed. The capsule measures the acid refluxing into the esophagus and transmits this information to a receiver that is worn at the waist. After the study, usually after 48 hours, the information from the receiver is downloaded into a computer and analyzed. The capsule falls off of the esophagus after 3-5 days and is passed in the stool. (The capsule is not reused.)
The advantage of the capsule over standard pH testing is that there is no discomfort from a catheter that passes through the throat and nose. Moreover, with the capsule, patients look normal (they don't have a catheter protruding from their noses) and are more likely to go about their daily activities, for example, go to work, without feeling self-conscious. Because the capsule records for a longer period than the catheter (48 versus 24 hours), more data on acid reflux and symptoms are obtained. Nevertheless, it is not clear whether obtaining additional information is important.
Capsule pH testing is expensive. Sometimes the capsule does not attach to the esophagus or falls off prematurely. For periods of time the receiver may not receive signals from the capsule, and some of the information about reflux of acid may be lost. Occasionally there is pain with swallowing after the capsule has been placed, and the capsule may need to be removed endoscopically. Use of the capsule is an exciting use of new technology although it has its own specific problems.
Esophageal motility testing
Esophageal motility testing determines how well the muscles of the esophagus are working. For motility testing, a thin tube (catheter) is passed through a nostril, down the back of the throat, and into the esophagus. On the part of the catheter that is inside the esophagus are sensors that sense pressure. A pressure is generated within the esophagus that is detected by the sensors on the catheter when the muscle of the esophagus contracts. The end of the catheter that protrudes from the nostril is attached to a recorder that records the pressure. During the test, the pressure at rest and the relaxation of the lower esophageal sphincter are evaluated. The patient then swallows sips of water to evaluate the contractions of the esophagus.
Esophageal motility testing has two important uses in evaluating GERD. The first is in evaluating symptoms that do not respond to treatment for GERD since the abnormal function of the esophageal muscle sometimes causes symptoms that resemble the symptoms of GERD. Motility testing can identify some of these abnormalities and lead to a diagnosis of an esophageal motility disorder. The second use is evaluation prior to surgical or endoscopic treatment for GERD. In this situation, the purpose is to identify patients who also have motility disorders of the esophageal muscle. The reason for this is that in patients with motility disorders, some surgeons will modify the type of surgery they perform for GERD.
Gastric emptying studies
Gastric emptying studies are studies that determine how well food empties from the stomach. As discussed above, about 20 % of patients with GERD have slow emptying of the stomach that may be contributing to the reflux of acid. For gastric emptying studies, the patient eats a meal that is labeled with a radioactive substance. A sensor that is similar to a Geiger counter is placed over the stomach to measure how quickly the radioactive substance in the meal empties from the stomach.
Information from the emptying study can be useful for managing patients with GERD. For example, if a patient with GERD continues to have symptoms despite treatment with the usual medications, doctors might prescribe other medications that speed-up emptying of the stomach. Alternatively, in conjunction with GERD surgery, they might do a surgical procedure that promotes a more rapid emptying of the stomach. Nevertheless, it is still debated whether a finding of reduced gastric emptying should prompt changes in the surgical treatment of GERD.
Symptoms of nausea, vomiting, and regurgitation may be due either to abnormal gastric emptying or GERD. An evaluation of gastric emptying, therefore, may be useful in identifying patients whose symptoms are due to abnormal emptying of the stomach rather than to GERD.
Acid perfusion test
The acid perfusion (Bernstein) test is used to determine if chest pain is caused by acid reflux. For the acid perfusion test, a thin tube is passed through one nostril, down the back of the throat, and into the middle of the esophagus. A dilute, acid solution and a physiologic salt solution (similar to the fluid that bathes the body's cells) are alternately poured (perfused) through the catheter and into the esophagus. The patient is unaware of which solution is being infused. If the perfusion with acid provokes the patient's usual pain and perfusion of the salt solution produces no pain, it is likely that the patient's pain is caused by acid reflux.
The acid perfusion test, however, is used only rarely. A better test for correlating pain and acid reflux is a 24-hour esophageal pH or pH capsule study during which patients note when they are having pain. It then can be determined from the pH recording if there was an episode of acid reflux at the time of the pain. This is the preferable way of deciding if acid reflux is causing a patient's pain. It does not work well, however, for patients who have infrequent pain, for example every two to three days, which may be missed by a one or two day pH study. In these cases, an acid perfusion test may be reasonable.