Overview of neurogastroenterology-gastrointestinal motility and functional GI disorders: classification, prevalence, and epidemiology.

The classification of gastrointestinal (GI) motility and functional gastrointestinal disorders is in a state of transition. Functional GI disorders are classified by their symptom complex, and the epidemiology of these conditions is based on symptom surveys. In contrast, GI motility disorders are classified by results of GI motility testing; the epidemiology of these conditions is often derived from tertiary care centers. Over time, with increasingly sophisticated methods of studying the brain-gut axis, the classification will likely shift from symptoms to a classification based on pathophysiology. This article reviews the epidemiology of these common disorders from the esophagus to the anorectum.