Functional gastrointestinal disorders


Functional gastrointestinal disorders (FGID), also known as disorders of gut-brain interaction, include a number of separate idiopathic disorders which affect different parts of the gastrointestinal tract and involve visceral hypersensitivity and motility disturbances.



Functional bowel disorder refer in medicine to a group of bowel disorders which are characterised by chronic abdominal complaints without a structural or biochemical cause that could explain symptoms. 



Other functional disorders relate to other aspects of the process of digestion.



The Rome process, has helped to define the functional gastrointestinal disorders.



The current Rome IV classification: 



A. Esophageal disorders



A1. Functional chest pain


A2. Functional heartburn


A3. Reflux hypersensitivity


A4. Globus


A5. Functional dysphagia


B. Gastroduodenal disorders



B1. Functional dyspepsia


B1a. Postprandial distress syndrome (PDS)


B1b. Epigastric pain syndrome (EPS)


B2. Belching disorders


B2a. Excessive supragastric belching


B2b. Excessive gastric belching


B3. Nausea and vomiting disorders


B3a. Chronic nausea vomiting syndrome (CNVS)


B3b. Cyclic vomiting syndrome (CVS)


B3c. Cannabinoid hyperemesis syndrome (CHS)


B4. Rumination syndrome


C. Bowel disorders



C1. Irritable bowel syndrome (IBS)


IBS with predominant constipation (IBS-C)


IBS with predominant diarrhea (IBS-D)


IBS with mixed bowel habits (IBS-M)


IBS unclassified (IBS-U)


C2. Functional constipation


C3. Functional diarrhea


C4. Functional abdominal bloating/distension


C5. Unspecified functional bowel disorder


C6. Opioid-induced constipation


D. Centrally mediated disorders of gastrointestinal pain



D1. Centrally mediated abdominal pain syndrome (CAPS)


D2. Narcotic bowel syndrome (NBS)/ Opioid-induced GI hyperalgesia


E. Gallbladder and sphincter of Oddi disorders



E1. Biliary pain


E1a. Functional gallbladder disorder


E1b. Functional biliary sphincter of Oddi disorder


E2. Functional pancreatic sphincter of Oddi disorder


F. Anorectal disorders



F1. Fecal incontinence


F2. Functional anorectal pain


F2a. Levator ani syndrome


F2b. Unspecified functional anorectal pain


F2c. Proctalgia fugax


F3. Functional defecation disorders


F3a. Inadequate defecatory propulsion


F3b. Dyssynergic defecation


G. Childhood functional GI disorders: Neonate/Toddler



G1. Infant regurgitation


G2. Rumination syndrome


G3. Cyclic vomiting syndrome (CVS)


G4. Infant colic


G5. Functional diarrhea


G6. Infant dyschezia


G7. Functional constipation


H. Childhood functional GI disorders: Child/Adolescent



H1. Functional nausea and vomiting disorders


H1a. Cyclic vomiting syndrome (CVS)


H1b. Functional nausea and functional vomiting


H1b1. Functional nausea


H1b2. Functional vomiting


H1c. Rumination syndrome


H1d. Aerophagia


H2. Functional abdominal pain disorders


H2a. Functional dyspepsia


H2a1. Postprandial distress syndrome


H2a2. Epigastric pain syndrome


H2b. Irritable bowel syndrome (IBS)


H2c. Abdominal migraine


H2d. Functional abdominal pain ? NOS


H3. Functional defecation disorders


H3a. Functional constipation


H3b. Nonretentive fecal incontinence


Epidemiology Edit



Functional gastrointestinal disorders are very common. Globally, irritable bowel syndrome and functional dyspepsia alone may affect 16-26% of the population.



FGIDs share in common any of several physiological features including increased motor reactivity, enhanced visceral hypersensitivity, altered mucosal immune and inflammatory function (associated with bacterial dysbiosis), and altered central nervous system and enteric nervous system (CNS-ENS) regulation.



There are complex interactions between these factors through the brain-gut axis.



These factors affect how FGID manifest in terms of symptoms but also affect the clinical outcome. 



These factors are interconnected and the influences on these factors are bidirectional and mutually interactive.



In FGIDs diet, microbiome, genetics, neuromuscular function and immunological response all interact.


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