Fundamentals of neurogastroenterology: Physiological aspects and clinical implications

The digestive tract plays a key role in maintaining homeostasis and the general well-being of the human body via complex physiological functions. These gastrointestinal functions include motility; mixing of ingesta with pancreatic, biliary, and enteric secretions; absorption of digested nutrients; and disposal of undigested residues. Such processes usually occur without conscious perception. However, approximately 30%-40% of the general population report digestive symptoms, often triggered by meal intake. Most of these people will be labeled as having a disorder of gut-brain interaction (DGBI). The pathophysiology of DGBI is complex and not only involves bidirectional dysregulation of gut-brain interaction (via the gut-brain axis), but also microbial dysbiosis within the gut, altered mucosal immune function, increased epithelial barrier permeability, visceral hypersensitivity, and abnormal gastrointestinal motility. In this article, normal physiology and pathophysiology of gastrointestinal function and processes underlying symptom generation are reviewed. This article provides a thorough appraisal of symptom profiles, pathogenesis, and functional tests of the wide array of DGBI.