**2. Pathogenesis and evaluation**

Different factors such as delayed gastric emptying (Stanghellini V et al., 1996; Sarnelli G et al., 2003), hypersensitivity to gastric distension (Bradette M et al., 1991; Mearin F et al., 1991; Barbera R et al., 1995; Tack J et al., 2001), impaired gastric accommodation to a meal (Tach J et al., 1998), abnormal duodenojejunal motility (Holtmann G et al., 1996; Wilmer A et al., 1998), duodenal motor and sensory dysfunction (Samsom M et al., 1999; Schwarz MP et al., 2001), duodenal hypersensitivity (Schwartz MP et al., 2001), *Helicobacter pylori* infection, and psychosocial factors have been implicated in the pathogenesis of FD. Among these factors, acid is thought to be more important because proton pump inhibitors (PPIs) and histamine 2 (H2)-receptor antagonists have been proposed to be effective therapies for a subset of patients with FD.
