Functional gastrointestinal (GI) and motility disorders are the most common GI disorders in the generalpopulation. Estimates vary, but about 1 in 4 people or more in the U.S. have one of these disorders. The conditions account for about 40% of GI problems seen by doctors and therapists.
Functional GI disorders are disorders of gut–brain interaction. It is a group of disorders classified by GI symptoms related to any combination of the following: motility disturbance, visceral hypersensitivity, altered mucosal and immune function, altered gut microbiota, and altered central nervous system (CNS) processing.
The term "functional" is generally applied to disorders where the body's normal activities in terms of the movement of the intestines, the sensitivity of the nerves of the intestines, or the way in which the brain controls some of these functions is impaired.
However, there are no structural abnormalities that can be seen by endoscopy, x-ray, or blood tests. Thus it is identified by the characteristics of the symptoms and infrequently, when needed, limited tests. The Rome diagnostic criteria categorize the functional gastrointestinal disorders – disorders of gut-brain interaction – and define symptom based diagnostic criteria for each category.