Dyspepsia, which has multiple causes, is either organic or functional. Organic dyspepsia refers to conditions caused by diseases of the upper gastrointestinal tract - particularly peptic ulcers, as well as oesophageal and gastric cancer - that can be detected during an examination. Functional dyspepsia is the default diagnosis when a thorough clinical investigation does not point to an organic cause or demonstrably impaired gastrointestinal function. Gastro-oesophageal reflux disease (GERD) involves the backflow of stomach contents through the lower oesophageal sphincter into the oesophagus, typically causing the symptoms of heartburn and acid regurgitation or waterbrash (bitter regurgitation). Oeso- phagitis can sometimes be detected by an OGD.