Cough and gastroesophageal reflux: from the gastroenterologist end

Gastroesophageal reflux (GER) is one of the three most common causes of chronic unexplained cough. Diagnosing GER-related cough is challenging since many patients do not have esophagitis or an increased esophageal acid exposure during 24 h esophageal pH-metry. A significant time association between acid reflux and cough can be demonstrated in a subgroup of patients, even if the total esophageal acid exposure is normal. Establishing an exact time relationship between reflux and cough requires objective measurements of both cough and reflux episodes. A variety of techniques for cough assessment are available, including sound recordings and continuous measurement of gastroesophageal pressures. The Symptom Association Probability (SAP) has been suggested as the most reliable algorithm to establish the non-chance association between GER and cough. Although the relationship between acid reflux and cough is generally accepted, the response rate of patients with chronic unexplained cough to proton pump inhibitor treatment (PPI) is poorer compared to that in patients with typical GERD symptoms. Combined impedance-pH recordings, a new technique for the measurement of all types of reflux, have recently shown that not only acid but also weakly acidic GER may be associated with cough. Moreover, measurements in patients "on" PPI therapy demonstrated that weakly acidic reflux may persist during PPI treatment and may be associated with cough. Aspiration of gastric contents into the lungs and a vagally mediated reflex arc, originating from the distal esophagus, have been proposed as pathophysiological mechanisms in GER-related cough. More recently, reflux induced bronchial hypersensitivity has been proposed as a third underlying mechanism. Treatment of GER-related cough remains challenging. So far, long term PPI treatments produce unsatisfactory results. In patients not responding to PPI, weakly acidic GER might still be the cause of cough. In these patients other therapeutic strategies i.e. abolishing all types of GER might need to be considered. Antireflux surgery has been performed successfully in a group of patients with GER-related cough. However, controlled, prospective outcome studies are necessary to confirm the role of antireflux treatments in the management of GER-related cough.