Gastro-oesophageal reflux disease Gastro-oesophageal reflux resulting in heaburn affects approximately 30% of the general population. Pathophysiology Occasional episodes of gastro-oesophageal reflux are common in healthy individuals. Reflux is normally followed by oesophageal peristaltic waves that efficiently clear the gullet, alkaline saliva neutralises residual acid and symptoms do not occur. Gastro- oesophageal reflux disease develops when the oesophageal mucosa is exposed to gastroduodenal contents for prolonged periods of time, resulting in symptoms and, in a propoion of cases, oesophagitis. Abnormalities of the lower oesophageal sphincter The lower oesophageal sphincter is tonically contracted under normal circumstances, relaxing only during swallowing (p. 766). Some patients with gastro-oesophageal reflux disease have reduced lower oesophageal sphincter tone, permitting reflux when intra-abdominal pressure rises. In others, basal sphincter tone is normal but reflux occurs in response to frequent episodes of inappropriate sphincter relaxation. Hiatus hernia Hiatus hernia causes reflux because the pressure gradient is lost between the abdominal and thoracic cavities, which normally pinches the hiatus. In addition, the oblique angle between the cardia and oesophagus disappears. Many patients who have large hiatus hernias develop reflux symptoms but the relationship between the presence of a hernia and symptoms is poor. Hiatus hernia is very common in individuals who have no symptoms, and some symptomatic patients have only a very small or no hernia. Neveheless, almost all patients who develop oesophagitis, Barrett's oesophagus or peptic strictures have a hiatus hernia. Delayed oesophageal clearance Defective oesophageal peristaltic activity is commonly found in patients who have oesophagitis. It is a primary abnormality, since it persists after oesophagitis has been healed by acid-suppressing drug therapy. Poor oesophageal clearance leads to increased acid exposure time. Ref Davidson edition23rd pg791