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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