Functional dyspepsia (FD) is a type of functional gastrointestinal disorder. It is characterized by motility disorders of the stomach and duodenum, such as adaptive relaxation disorder and impaired gastric emptying, with microinflammation of the duodenum known to be a contributing factor. Duodenal microinflammation can be triggered by various causes, including exposure to gastric acid, stress, and the intestinal microbiota. Recent reports have also suggested that early chronic pancreatitis may overlap with refractory FD, and the involvement of the duodenal trypsin receptor, protease-activated receptor-2 (PAR2), is also suspected. Further investigation into the pathophysiology of the condition is warranted.