Overview of functional gastrointestinal disorders: dysfunction of the brain-gut axis.

Functional gastrointestinal disorders are common and incompletely understood. The gut is controlled by a complex interaction of sensory and motor neurons in the local enteric nervous system. Inputs from the central nervous system modify gut function, whereas inputs from the gut to the brain mediate symptoms. Dysfunction at one or more sites in the brain-gut axis is likely to produce the various functional gastrointestinal syndromes. Therapies likewise can be directed at one or more levels.