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Beyond the EsophagusAn interesting series of meetings were held during Digestive Disease Week (May 2001), and one of topics of discussion was called Beyond the Esophagus - the Evolving Management of Extra-esophageal Presentations of Gastroesophageal Reflux DiseaseThis part of the symposium suggested that about 20% of adults have frequent "classic" symptoms of gastroesophageal reflux disease (GERD): heartburn or regurgitation. Yet, in addition to the classic definition of this disorder, GERD is also becoming associated with many extraesophageal disorders. These include: pulmonary diseases (asthma, chronic cough, recurrent bronchitis, sleep apnea, and pulmonary fibrosis), laryngeal diseases (laryngitis, subglottic stenosis, and laryngeal cancer), and other ENT (ear, nose, throat) disorders (sinusitis, pharyngitis, and dental erosion). While there is no direct evidence yet, it is hypothesized that GERD may cause these disorders, either by direct mucosal injury and/or by triggering neural mechanisms such as vagal nerve mediation of increased airway secretions and bronchospasm. Since the advent of treatment with proton-pump inhibitors or surgical intervention, there has been growing evidence (although no controlled studies) that treatment leads to improvement or resolution of symptoms in a subset of patients with these disorders. Therefore, more and more physicians may in the future consider a diagnosis of GERD in the diagnosis of persons persons with extra-esophageal diseases. Yet, many of those with extraesophageal symptoms of GER do not have the classic symptoms, and very few have endoscopic evidence of reflux esophagitis. Since 24-hr pH monitoring is typically used to look for evidence of acid reflux, and this test is not comfortable, it is avoided. In addition, there is still controversy regarding the optimal site of probe placement (ie, pharyngeal vs upper esophageal) and the determination of what is a normal vs abnormal amount of acid reflux. In general, normal pH testing in the upper and lower esophagus is strong evidence against acid-related symptoms. But due to the difficulties associated with pH testing, false-negatives may occur. On the other hand, a positive test merely confirms the presence of acidic reflux, but does not prove a causative relationship to the symptoms. And, pH testing only detects acidic refluxate; and it is conceivable that nonacidic reflux may also play a pathophysiologic role in the symptoms of some patients. Can�t They Come Up with Something Better Than Esophageal pH Testing? A catheter-free pH-monitoring system is being tested. Since so many people refuse to have an esophageal pH monitoring done, some investigators from the University of Southern California in Los Angeles are trying a new methodology in a small study involving a catheter-free ambulatory esophageal pH-monitoring system made by Bravo; Endonetics; San Diego, CA. In this procedure, a miniature pH probe the size of a gel cap, is passes orally or nasally by catheter into the esophagus,. It is then attached via suction and a small pin to the mucosal lining, at which time the catheter is removed, leaving the pH probe to transmit pH data via radio signals to a small pager-sized receiver worn by the patient. The small probe transmits data for an average of almost 48 hours before detaching. In a controlled study of (only) 7 persons without symptoms, 3 underwent pH monitoring with the micro-probe alone, and 4 with both the micro-probe as well as a conventional catheter-based pH-monitoring system performed concurrently. Adequate monitoring was found for 88% of the recording period - and the small amounts of measured acid reflux appeared comparable to that obtained with the conventional pH probe. The new technology, which is already being marketed, is said to need more study, however to determine accuracy, reliability, and patient acceptance. What Is the Mechanism of GERD and Chronic Cough and How Can a Cause-and-Effect Relationship Be Shown?The mechanisms through which GERD may cause chronic cough remain controversial. The major portion of the trachea, bronchus and esophagus derive from common embryonic origins, and are innervated by the vagus nerve. It is thought that GERD can cause cough or asthma either through microaspiration, or by stimulation of a vagally mediated esophageal-bronchial reflex. Is There a Common Center in the Brain Stem That is Involved?Catheters were inserted in rats, either to the distal esophagus or into the trachea.1.For animals with an esophageal cannula, acid reflux was simulated in the distal esophagus for 50 minutes. 2.For animals with the tracheal catheter, mechanical irritation of the trachea and larynx was given for 30 minutes. 3.Control animals had catheter placement but no acid infusion or mechanical irritation.In all animals, various brain centers were looked at for neuronal activation. The results showed that esophageal acid perfusion and laryngotracheal stimulation (in comparison to controls) increased neuronal activation in several areas of the brain. With the exception of only one center, stimulation of both the esophagus and trachea led to activation of the same central nervous system (CNS) centers. It is therefore though that chronic GER may lead to activation of CNS centers that may then reflexively lead to chronic cough. Unfortunately, although treatment of GER may eliminate ongoing CNS stimulation, it is possible that these centers may continue to stimulate coughing, independent of GERD. Future treatments for cough may have to target the CNS centers as well as reducing GER.
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