The frontiers of reflux disease

Gastroesophageal reflux disease has frequently been implicated in a wide variety of complications beyond the esophagus. These so-called "extraesophageal" disorders range from diseases of the respiratory tract, such as asthma and bronchitis, to more remote sites and conditions such as otitis and dental erosion. Many articles proposing a link between reflux disease and a multitude of extraesophageal complications have been published, but indisputable evidence that these conditions are caused by reflux disease is rare. Much of the support for a link between reflux disease and a number of extraesophageal complications is based on the observation that reflux disease frequently coexists with other disorders. A causal link is difficult to prove, however, and this review aims to critically evaluate the available evidence, looking, where possible, at longitudinal studies, expert diagnoses, and response to acid-suppressive therapy as a means of determining the true relationship between GERD and its putative extraesophageal complications.