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
The gastrointestinal tract (GI tract, digestive tract, alimentary canal) is the tract or passageway of the digestive system that leads from the mouth to the anus. The GI tract contains all the major organ (biology), organs of the digestive syste ...
and involve
visceral hypersensitivity and
motility disturbances.
[ ]
Definition of functional gastrointestinal disorders/disorders of gut-brain interaction
Using the Delphi method, the
Rome Foundation and its board of directors, chairs and co-chairs of the
ROME IV
The Rome process and Rome criteria are an international effort to create scientific data to help in the diagnosis and treatment of functional gastrointestinal disorders, such as irritable bowel syndrome, functional dyspepsia and rumination syndrome ...
committees developed the current definition for disorders of gut-brain interaction.
[Drossman DA. The Rome IV Committees, editor. Functional Gastrointestinal Disorders and the Rome IV process. In: Drossman DA, Chang L, Chey WD, Kellow J, Tack J, Whitehead WE, editors. Rome IV functional gastrointestinal disorders: disorders of gut-brain interaction. I. Raleigh, NC: The Rome Foundation; 2016. pp. 1–32.]
A group of disorders classified by GI symptoms related to any combination of:
* Motility disturbance
*
Visceral hypersensitivity
* Altered mucosal and immune function
* Altered
gut microbiota
Gut microbiota, gut microbiome, or gut flora, are the microorganisms, including bacteria, archaea, fungi, and viruses that live in the digestive tracts of animals. The gastrointestinal metagenome is the aggregate of all the genomes of the gut m ...
* Altered
central nervous system (CNS) processing
Classification
Terms such as ''functional colonic disease'' (or ''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 consensus review process of meetings and publications organised by the Rome Foundation, known as the
Rome process, has helped to define the functional gastrointestinal disorders.
Successively, the Rome I, Rome II, Rome III and Rome IV proposed consensual classification system and terminology, as recommended by the Rome Coordinating Committee. These now include classifications appropriate for adults, children and neonates/toddlers.
The current
ROME IV classification, published in 2016, is as follows:
A. Esophageal disorders
* A1. Functional
chest pain
Chest pain is pain or discomfort in the chest, typically the front of the chest. It may be described as sharp, dull, pressure, heaviness or squeezing. Associated symptoms may include pain in the shoulder, arm, upper abdomen, or jaw, along with n ...
* A2.
Functional heartburn
* A3.
Reflux hypersensitivity
* A4.
Globus
* A5. Functional
dysphagia
B. Gastroduodenal disorders
* B1.
Functional dyspepsia
Indigestion, also known as dyspepsia or upset stomach, is a condition of impaired digestion. Symptoms may include upper abdominal fullness, heartburn, nausea, belching, or upper abdominal pain. People may also experience feeling full earlier t ...
** 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
Cyclic vomiting syndrome (CVS) is a chronic functional condition of unknown pathogenesis. CVS is characterized as recurring episodes lasting a single day to multiple weeks. Each episode is divided into four phases: inter-episodic, prodrome, vom ...
(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
Opioids are substances that act on opioid receptors to produce morphine-like effects. Medically they are primarily used for pain relief, including anesthesia. Other medical uses include suppression of diarrhea, replacement therapy for opioid use ...
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
The pancreas is an Organ (anatomy), organ of the digestive system and endocrine system of vertebrates. In humans, it is located in the abdominal cavity, abdomen behind the stomach and functions as a gland. The pancreas is a mixed or heterocrine ...
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
Baby colic, also known as infantile colic, is defined as episodes of crying for more than three hours a day, for more than three days a week, for three weeks in an otherwise healthy child. Often crying occurs in the evening. It typically does no ...
* G5. Functional diarrhea
* G6. Infant
dyschezia
Constipation is a bowel dysfunction that makes bowel movements infrequent or hard to pass. The stool is often hard and dry. Other symptoms may include abdominal pain, bloating, and feeling as if one has not completely passed the bowel movement ...
* 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
Abdominal migraine is a variant type of migraine. It primarily affects Child, children, and is rare in Adult, adults. It mainly causes episodes of abdominal pain without an accompanying headache. It is poorly understood. It is difficult to confirm ...
** H2d. Functional abdominal pain ‒ NOS
* H3. Functional defecation disorders
** H3a. Functional constipation
** H3b. Nonretentive fecal incontinence
Causes
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
Dysbiosis (also called dysbacteriosis) is characterized by a disruption to the microbiome resulting in an imbalance in the microbiota, changes in their functional composition and metabolic activities, or a shift in their local distribution. For ex ...
), and altered central nervous system and
enteric nervous system (CNS-ENS) regulation.
The pathophysiology of FGID has been best conceptualized using biopsychosocial model help to explain the relationships between an individual factors in their early life that in turn can influence their psychosocial factor and physiological functioning. This model also shows the complex interactions between these factors through the brain-gut axis.
[Drossman DA. The Rome IV Committees, editor. Functional Gastrointestinal Disorders and the Rome IV process. In: Drossman DA, Chang L, Chey WD, Kellow J, Tack J, Whitehead WE, editors. Rome IV functional gastrointestinal disorders: disorders of gut-brain interaction.I. Raleigh, NC: The Rome Foundation; 2016. pp 1–32.] 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.
Early life factors
Early life factors include genetic factors, psychophysiological and sociocultural factors, and environmental exposures.
* Genetics – Several
polymorphism
Polymorphism, polymorphic, polymorph, polymorphous, or polymorphy may refer to:
Computing
* Polymorphism (computer science), the ability in programming to present the same programming interface for differing underlying forms
* Ad hoc polymorphis ...
s and candidate genes may predispose individuals to develop FGID. These include
alpha-2 adrenergic and
5-HT receptor
5-HT receptors, 5-hydroxytryptamine receptors, or serotonin receptors, are a group of G protein-coupled receptor and ligand-gated ion channels found in the central and peripheral nervous systems. They mediate both excitatory and inhibitory neur ...
s;
serotonin
Serotonin () or 5-hydroxytryptamine (5-HT) is a monoamine neurotransmitter. Its biological function is complex and multifaceted, modulating mood, cognition, reward, learning, memory, and numerous physiological processes such as vomiting and vas ...
and
norepinephrine transporters (SERT, NET); inflammatory markers
interleukin-(IL)10,
tumor necrosis factor-(TNF) alpha, and TNF super family member 15 (TNF-SF15); intracellular cell signaling (
G proteins); and ion channels (SCN5A). However, the expression of a FGID requires the influence of additional environmental exposures such as infection, illness modeling and other factors.
* Psychophysiological factors may affect the expression of these genes, thus leading to symptoms production associated with FGID.
* Sociocultural factors and family interactions have been shown to shape later reporting of symptoms, the development of FGIDs, and health care seeking. The expression of pain varies across cultures as well including denial of symptoms to dramatic expression.
* Environmental exposures – Prior studies have shown the effect of environmental exposures in relation to the development of FGIDs. Environmental exposures such as childhood salmonella infection can be a risk factor for IBS in adulthood.
Psychosocial factors
Psychosocial factors influence the functioning of the GI tract through the brain-gut axis (motility, sensitivity, barrier function). They also affect experience and behavior, treatment selection and the clinical outcome. Psychological stress or one's emotional response to stress exacerbates gastrointestinal symptoms and may contribute to FGID development.
Physiology
The physiology of FGID is characterized by abnormal motility, visceral hypersensitivity as well as dysregulation of the immune system and barrier function of the GI tract as well as inflammatory changes.
* Abnormal motility
Studies have shown altered muscle contractility and tone, bowel compliance, and transit may contribute to many of the gastrointestinal symptoms of FGID which may include diarrhea, constipation, and vomiting.
* Visceral hypersensitivity
In FGID there is poor association of pain with GI motility in many functional GI disorders. These patient often have a lower pain threshold with balloon distension of the bowel (visceral hyperalgesia), or they have increased sensitivity even to normal intestinal function; Visceral hypersensitivity may be amplified in patients with FGIDs.
* Immune dysregulation, inflammation, and barrier dysfunction
Studies on postinfectious IBS have shown that factors such as mucosal membrane permeability, the intestinal flora, and altered mucosal immune function. Ultimately leading to visceral hypersensitivity. Factors contributing to this occurrence include genetics, psychological stress, and altered receptor sensitivity at the gut mucosa and myenteric plexus, which are enabled by mucosal immune dysfunction.
* Microbiome
There has been increased attention to the role of bacteria and the microbiome in overall health and disease. There is evidence for a group of microorganisms which play a role in the brain-gut axis. Studies have revealed that the bacterial composition of the gastrointestinal tract in IBS patient differs from healthy individuals (e.g., increased Firmicutes and reduced Bacteroidetes and Bifidobacteria) However, further research is needed to determine the role of the microbiome in FGIDs.
* Food and diet
The types of food consumed and diet consumed plays a role in the manifestation of FGID and also their relationship to intestinal microbiota. Studies have shown that specific changes in diet (e.g., low FODMAP—fermentable oligo-, di-, and monosaccharides and polyols, or gluten restriction in some patients) may help and reduce the symptom burden in FGID. However, no one diet has been shown to be recommended for all people.
Brain-gut axis
The brain-gut axis is the mechanism in which the psychosocial factors influence the GI tract and vice versa. There is communication between emotional and cognitive centers of the brain to the GI tract and vice versa. Emotions have been shown to stimulate colon motor function and result in decreased colonic transit time, increased contractile activity, the induction of defecation, and symptoms of diarrhea.
Epidemiology
Functional gastrointestinal disorders are very common. Globally, irritable bowel syndrome and functional dyspepsia alone may affect 16–26% of the population.
Research
There is considerable research into the causes, diagnosis and treatments for FGIDs. Diet, microbiome, genetics, neuromuscular function and immunological response all interact.
A role for mast cell activation has been proposed as one of the factors.
See also
*
Allergy
*
Food intolerance
*
Functional indigestion
*
Histamine intolerance
References
External links
{{Portal bar, Medicine
Gastrointestinal tract disorders