Irritable bowel syndrome pathophysiology: Difference between revisions

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{{Irritable bowel syndrome}}
{{Irritable bowel syndrome}}
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{{CMG}}; {{AE}} {{Cherry}}
==Overview==
==Overview==
[[Irritable bowel syndrome|Irritable Bowel Syndrome]] is caused by a complex interaction of various factors such as intrinsic [[Gastrointestinal tract|gastrointestinal]] factors, [[CNS]] dysregulation and [[psychosocial]] factors, genetic, and environmental factors. Intrinsic gastrointestinal factors include [[Motor skill|motor]] abnormalities, [[Viscus|visceral]] [[hypersensitivity]], [[Immunity (medical)|immune]] activation, [[Mucous membrane|mucosal]] inflammation, altered [[Gut flora|gut microbiota]], and abnormal [[serotonin]] pathways. [[Viscus|Visceral]] [[hypersensitivity]] refers to a decreased threshold for the perception of [[Viscus|visceral]] stimuli that affects [[Spinal cord|spinal]] excitability, [[brain stem]] and [[Cortical area|cortical]] modulation, activation of specific [[Gastrointestinal tract|gastrointestinal]] mediators, and recruitment of peripheral silent [[Nociceptor|nociceptors]]. [[Immunity (medical)|Immune]] activation and [[Mucous membrane|mucosal]] inflammation involves an interaction of [[Lymphocyte|lymphocytes]], [[Mast cell|mast cells]], and [[Cytokines|proinflammatory cytokines]]. Environmental factors encompass dietary changes and [[Infection|infections]]. [[Psychosocial]] factors such as [[Stress (medicine)|stress]], [[anxiety]], and [[depression]] directly shape adult connectivity in the executive control network consisting of structures such as the [[Insular cortex|insula]], anterior [[cingulate cortex]], and the [[thalamus]]. Semipermanent or permanent changes in complex [[Nervous system|neural]] circuits lead to central pain amplification contributing to [[abdominal pain]] in [[Irritable bowel syndrome|IBS]] patients. The dorsolateral [[prefrontal cortex]] activity (responsible for vigilance and alertness of the human brain) and the mid-[[Cingulate cortex|cingulate corte]]<nowiki/>x (engaged in attention pathways and responses) is reduced in [[Irritable bowel syndrome|IBS]] patients. This reduction may lead to alterations in the subjective sensations of pain. Genetic factors also play a role in [[Irritable bowel syndrome|IBS]]. IBS has a high twin [[Concordance (genetics)|concordance]] and familial aggregation. IBS is associated with [[single nucleotide polymorphisms]] ([[Single nucleotide polymorphism|SNPs]]) in genes involved in [[Immunity (medical)|immune]] activation, [[neuropeptide]] hormone function, [[oxidative stress]], [[Pain and nociception|nociception]], [[permeability]] of the GI tract, host-[[Microbiome|microbiota]] interaction, inflammation, and [[Tumor necrosis factors|TNF]] activity.


==Pathophysiology==
==Pathophysiology==
Initially, IBS was considered a psychosomatic illness, and the involvement of biological and pathogenic factors was not verified until the 1990s, a process common in the [[history of emerging infectious diseases]]. The risk of developing IBS increases six-fold after acute gastrointestinal infection. Post-infection, further risk factors are young age, prolonged [[fever]], [[anxiety]] and [[depression]].<ref>{{cite journal | author = Thabane M, Kottachchi DT, Marshall JK | title = The incidence and prognosis of post-infectious irritable bowel syndrome. | journal = Aliment Pharmacol Ther | volume = 26 | issue = 4 | pages = 535-44 | year = 2007 | pmid = 17661757}}</ref>


===Psychosomatic illness===
===Pathogenesis===
One of the first references to the concept of an "Irritable Bowel" appeared in the Rocky Mountain Medical Journal in 1950.<ref name="BROWN_1950">{{cite journal |author=BROWN PW |title=The irritable bowel syndrome |journal=Rocky Mountain medical journal|volume=47 |issue=5 |pages=343-6 |year=1950 |pmid=15418074 |doi=}}</ref> The term was used to categorize patients who developed symptoms of diarrhea, abdominal pain, constipation, but where no well-recognized infective cause could be found.  Early theories suggested that the Irritable Bowel was caused by a [[Somatoform disorder|somatic]], or mental disorder.  One paper from the 1980s investigated "learned illness behavior" in patients with IBS and [[peptic ulcers]].<ref name="WHITEHEAD_1982">{{cite journal |author=Whitehead WE, Winget C, Fedoravicius AS, Wooley S, Blackwell B|title=Learned illness behavior in patients with irritable bowel syndrome and peptic ulcer |journal=Dig. Dis. Sci. |volume=27|issue=3 |pages=202-8 |year=1982 |pmid=7075418 |doi=}}</ref> Another study suggested that both IBS and stomach ulcer patients would benefit from 15 months of [[psychotherapy]].<ref name="pmid3895386">{{cite journal |author=Svedlund J, Sjödin I |title=A psychosomatic approach to treatment in the irritable bowel syndrome and peptic ulcer disease with aspects of the design of clinical trials |journal=Scand. J. Gastroenterol. Suppl. |volume=109 |issue= |pages=147-51 |year=1985 |pmid=3895386 |doi=}}</ref> Later, it was found that most stomach ulcers were caused by a bacterial infection with ''[[Helicobacter pylori]].''<ref name="pmid9191460">{{cite journal |author=Damianos AJ, McGarrity TJ |title=Treatment strategies for Helicobacter pylori infection|journal=American family physician |volume=55 |issue=8 |pages=2765–74, 2784–6 |year=1997 |pmid=9191460 |doi=}}</ref>
IBS occurs as a result of an interplay between four main factors:
{{Family tree/start}}


Additional publications suggesting the role of brain-gut "axis" appeared in the 1990s, such as a study entitled ''Brain-gut response to stress and cholinergic stimulation in IBS'' published in the ''Journal of Clinical Gastrotnerology'' in 1993.<ref>{{cite journal|author=Fukudo S, Nomura T, Muranaka M, Taguchi F |title=Brain-gut response to stress and cholinergic stimulation in irritable bowel syndrome. A preliminary study |journal=J. Clin. Gastroenterol. |volume=17 |issue=2 |pages=133-41 |year=1993 |pmid=8031340|doi=}}</ref>  A 1997 study published in ''Gut'' magazine suggested that IBS was associated with a "derailing of the brain-gut axis."<ref>{{cite journal |author=Orr WC, Crowell MD, Lin B, Harnish MJ, Chen JD |title=Sleep and gastric function in irritable bowel syndrome: derailing the brain-gut axis |journal=Gut |volume=41 |issue=3 |pages=390-3 |year=1997 |pmid=9378397 |doi=}}</ref>


<div class="noprint" style="clear: center; border: solid #aaa 1px; margin: 0 0 1em 1em;  background: #efeff9; width: 50%; padding: 4px; text-align: justify; float: center;">
{{Family tree | | | | | | B01 | | | |B01='''[[CNS]] dysregulation and [[psychosocial factors]]''' }}
{{Family tree | | | | | | |!| | | | | }}
{{Family tree | | | | | | |!| | | | | }}
{{familytree |boxstyle=text-align: left; | A01 |-|-| A02 |-|-|-| A03 | |A01= '''Intrinsic [[gastrointestinal]] factors''': <br> • [[Motor]] abnormalities <br>• [[Visceral]] [[hypersensitivity]] <br>• [[Immune]] activation and [[mucosal]] inflammation <br>• Altered [[gut]] [[microbiota]] <br>• Abnormal [[serotonin]] pathways | A02= '''IRRITABLE BOWEL SYNDROME'''| A03='''Genetic factors''': <br>• Twin concordance <br>• Familial aggregation <br>• [[SNPs|Single nucleotide polymorphisms(SNPs)]] <br>• TNF polymorphism}}


{{"
|There was a greater improvement in the psychotherapy groups for patients with IBS after three months and for both IBS and PUD (peptic ulcer disease) patients after 15 months. The difference had become more pronounced after 15 months, with the patients given psychotherapy showing further improvement, and the patients who had received medical treatment only showing some deterioration.
|by J Svedlund, ''A psychosomatic approach to treatment in the irritable bowel syndrome and peptic ulcer disease with aspects of the design of clinical trials'', 1985. 
}}


''Most peptic ulcers are now treated with 1-2 weeks of antibiotic therapy, since it has been discovered that they are caused by a combination of a genetic trait in the patient and infection with the bacteria [[H. Pylori]].''<ref name="EL-OMAR_2000"> {{cite journal |author=El-Omar EM, Carrington M, Chow WH, ''et al'' |title=Interleukin-1 polymorphisms associated with increased risk of gastric cancer |journal=Nature |volume=404 |issue=6776 |pages=398-402 |year=2000 |pmid=10746728 |doi=10.1038/35006081}} </ref>
{{Family tree | | | | | | |!| | | | | }}
{{Family tree | | | | | | |!| | | | | }}
{{familytree |boxstyle=text-align: left; | | | | | | B01 | | | |B01= '''Environmental factors''': <br>•Diet <br>•[[Infections]]}}
{{Family tree/end}}


</div>
==='''Environmental factors'''===
*[[Diet (nutrition)|Diet]]
**Fermentable [[Oligosaccharide|oligosaccharides]], [[Monosaccharide|monosaccharides]],  [[Disaccharide|disaccharides]], and [[Polyol|polyols]] (FODMAPs) are present in stone fruits, artificial sweeteners, lactose-containing foods, and [[Legume|legumes]]. Changes in diet such as increased amounts  (FODMAPs) can alter [[Gut flora|gut microflora]].<ref name="pmid23935555">{{cite journal |vauthors=Muir JG, Gibson PR |title=The Low FODMAP Diet for Treatment of Irritable Bowel Syndrome and Other Gastrointestinal Disorders |journal=Gastroenterol Hepatol (N Y) |volume=9 |issue=7 |pages=450–2 |year=2013 |pmid=23935555 |pmc=3736783 |doi= |url=}}</ref>
***[[Fermentation (biochemistry)|Fermentation]] and [[Osmosis|osmotic]] effects of FODMAPs produce [[Abdominal pain|abdominal discomfort]] and [[diarrhea]] in IBS.
***FODMAPs yield carbon dioxide, methane, and hydrogen that are responsible for bloating.
**[[Osmosis|Osmotically]] active carbohydrate by products lead to [[diarrhea]] by enhancing [[Intestine|intestinal]] contractions and precipitating fluid secretion.<ref name="pmid23644955">{{cite journal |vauthors=Böhn L, Störsrud S, Törnblom H, Bengtsson U, Simrén M |title=Self-reported food-related gastrointestinal symptoms in IBS are common and associated with more severe symptoms and reduced quality of life |journal=Am. J. Gastroenterol. |volume=108 |issue=5 |pages=634–41 |year=2013 |pmid=23644955 |doi=10.1038/ajg.2013.105 |url=}}</ref><ref name="pmid7910231">{{cite journal |vauthors=Young E, Stoneham MD, Petruckevitch A, Barton J, Rona R |title=A population study of food intolerance |journal=Lancet |volume=343 |issue=8906 |pages=1127–30 |year=1994 |pmid=7910231 |doi= |url=}}</ref><ref name="pmid24336217">{{cite journal |vauthors=David LA, Maurice CF, Carmody RN, Gootenberg DB, Button JE, Wolfe BE, Ling AV, Devlin AS, Varma Y, Fischbach MA, Biddinger SB, Dutton RJ, Turnbaugh PJ |title=Diet rapidly and reproducibly alters the human gut microbiome |journal=Nature |volume=505 |issue=7484 |pages=559–63 |year=2014 |pmid=24336217 |pmc=3957428 |doi=10.1038/nature12820 |url=}}</ref><ref name="pmid26867199">{{cite journal |vauthors=Elli L, Tomba C, Branchi F, Roncoroni L, Lombardo V, Bardella MT, Ferretti F, Conte D, Valiante F, Fini L, Forti E, Cannizzaro R, Maiero S, Londoni C, Lauri A, Fornaciari G, Lenoci N, Spagnuolo R, Basilisco G, Somalvico F, Borgatta B, Leandro G, Segato S, Barisani D, Morreale G, Buscarini E |title=Evidence for the Presence of Non-Celiac Gluten Sensitivity in Patients with Functional Gastrointestinal Symptoms: Results from a Multicenter Randomized Double-Blind Placebo-Controlled Gluten Challenge |journal=Nutrients |volume=8 |issue=2 |pages=84 |year=2016 |pmid=26867199 |pmc=4772047 |doi=10.3390/nu8020084 |url=}}</ref><ref name="pmid26522233">{{cite journal |vauthors=Coletta M, Gates FK, Marciani L, Shiwani H, Major G, Hoad CL, Chaddock G, Gowland PA, Spiller RC |title=Effect of bread gluten content on gastrointestinal function: a crossover MRI study on healthy humans |journal=Br. J. Nutr. |volume=115 |issue=1 |pages=55–61 |year=2016 |pmid=26522233 |doi=10.1017/S0007114515004183 |url=}}</ref><ref name="pmid24308871">{{cite journal |vauthors=Yang J, Fox M, Cong Y, Chu H, Zheng X, Long Y, Fried M, Dai N |title=Lactose intolerance in irritable bowel syndrome patients with diarrhoea: the roles of anxiety, activation of the innate mucosal immune system and visceral sensitivity |journal=Aliment. Pharmacol. Ther. |volume=39 |issue=3 |pages=302–11 |year=2014 |pmid=24308871 |doi=10.1111/apt.12582 |url=}}</ref><ref name="pmid24445613">{{cite journal |vauthors=Staudacher HM, Irving PM, Lomer MC, Whelan K |title=Mechanisms and efficacy of dietary FODMAP restriction in IBS |journal=Nat Rev Gastroenterol Hepatol |volume=11 |issue=4 |pages=256–66 |year=2014 |pmid=24445613 |doi=10.1038/nrgastro.2013.259 |url=}}</ref>
*&nbsp;[[Infection]]
**[[Infection|Infectious]] [[gastroenteritis]] triggers micro [[inflammation]] and up to one third of [[irritable bowel syndrome]] cases follow [[Gastroenteritis|acute gastroenteritis.]]
**Micro [[inflammation]] of the [[Gastrointestinal tract|gut]] causes activation of the [[Lymphocyte|lymphocytes]], [[Mast cell|mast cells]] and pro inflammatory [[Cytokine|cytokines]] that stimulate the [[enteric nervous system]] and lead to abnormal [[Viscus|visceral]] and [[Motor skill|motor]] responses within the [[Gastrointestinal tract|gastrointestinal]] tract.
**[[Immunity (medical)|Immune]] activation due to GI [[infection]] also increases [[Enteroendocrine cells|enteroendocrine]] cells, calprotectin-positive [[Macrophage|macrophages]], [[Intraepithelial lymphocyte|intraepithelial]] [[Lymphocyte|lymphocytes]], and l[[Lamina propria|amina propria]] [[T cell|T cells]] which contribute directly to [[abdominal pain]] perception.&nbsp;<ref name="pmid20101257">{{cite journal |vauthors=Ohman L, Simrén M |title=Pathogenesis of IBS: role of inflammation, immunity and neuroimmune interactions |journal=Nat Rev Gastroenterol Hepatol |volume=7 |issue=3 |pages=163–73 |year=2010 |pmid=20101257 |doi=10.1038/nrgastro.2010.4 |url=}}</ref><ref name="pmid22730468">{{cite journal |vauthors=Simrén M, Barbara G, Flint HJ, Spiegel BM, Spiller RC, Vanner S, Verdu EF, Whorwell PJ, Zoetendal EG |title=Intestinal microbiota in functional bowel disorders: a Rome foundation report |journal=Gut |volume=62 |issue=1 |pages=159–76 |year=2013 |pmid=22730468 |pmc=3551212 |doi=10.1136/gutjnl-2012-302167 |url=}}</ref><ref name="pmid23580243">{{cite journal |vauthors=Ohman L, Simrén M |title=Intestinal microbiota and its role in irritable bowel syndrome (IBS) |journal=Curr Gastroenterol Rep |volume=15 |issue=5 |pages=323 |year=2013 |pmid=23580243 |doi=10.1007/s11894-013-0323-7 |url=}}</ref><ref name="pmid17148502">{{cite journal |vauthors=Posserud I, Stotzer PO, Björnsson ES, Abrahamsson H, Simrén M |title=Small intestinal bacterial overgrowth in patients with irritable bowel syndrome |journal=Gut |volume=56 |issue=6 |pages=802–8 |year=2007 |pmid=17148502 |pmc=1954873 |doi=10.1136/gut.2006.108712 |url=}}</ref><ref name="pmid22180058">{{cite journal |vauthors=Jeffery IB, O'Toole PW, Öhman L, Claesson MJ, Deane J, Quigley EM, Simrén M |title=An irritable bowel syndrome subtype defined by species-specific alterations in faecal microbiota |journal=Gut |volume=61 |issue=7 |pages=997–1006 |year=2012 |pmid=22180058 |doi=10.1136/gutjnl-2011-301501 |url=}}</ref><ref name="pmid19457422">{{cite journal |vauthors=Spiller R, Garsed K |title=Postinfectious irritable bowel syndrome |journal=Gastroenterology |volume=136 |issue=6 |pages=1979–88 |year=2009 |pmid=19457422 |doi=10.1053/j.gastro.2009.02.074 |url=}}</ref><ref name="pmid25611066">{{cite journal |vauthors=Joo YE |title=Alteration of fecal microbiota in patients with postinfectious irritable bowel syndrome |journal=J Neurogastroenterol Motil |volume=21 |issue=1 |pages=135–7 |year=2015 |pmid=25611066 |pmc=4288086 |doi=10.5056/jnm14133 |url=}}</ref><ref name="pmid10026328">{{cite journal |vauthors=Gwee KA, Leong YL, Graham C, McKendrick MW, Collins SM, Walters SJ, Underwood JE, Read NW |title=The role of psychological and biological factors in postinfective gut dysfunction |journal=Gut |volume=44 |issue=3 |pages=400–6 |year=1999 |pmid=10026328 |pmc=1727402 |doi= |url=}}</ref><ref name="pmid24646319">{{cite journal |vauthors=Nielsen HL, Engberg J, Ejlertsen T, Nielsen H |title=Psychometric scores and persistence of irritable bowel after Campylobacter concisus infection |journal=Scand. J. Gastroenterol. |volume=49 |issue=5 |pages=545–51 |year=2014 |pmid=24646319 |doi=10.3109/00365521.2014.886718 |url=}}</ref>
** The role of [[small intestinal bacterial overgrowth syndrome]] is strongest when testing with glucose breath tests (relative risk = 4.2) or jejunal aspirates (relative risk = 3.0) are compared among patients with IBS and controls<ref name="pmid31750966">{{cite journal| author=Ghoshal UC, Nehra A, Mathur A, Rai S| title=A meta-analysis on small intestinal bacterial overgrowth in patients with different subtypes of irritable bowel syndrome. | journal=J Gastroenterol Hepatol | year= 2020 | volume= 35 | issue= 6 | pages= 922-931 | pmid=31750966 | doi=10.1111/jgh.14938 | pmc= | url=https://www.ncbi.nlm.nih.gov/entrez/eutils/elink.fcgi?dbfrom=pubmed&tool=sumsearch.org/cite&retmode=ref&cmd=prlinks&id=31750966  }} </ref>.


===Immune reaction===
==='''Intrinsic gastrointestinal factors'''===
*'''Motor abnormalities:'''
**IBS is referred to as ‘[[spastic colon]]’ due to changes in [[Colon (anatomy)|colonic]] [[Motor coordination|motor]] function.
**Manometry recordings from the [[Transverse colon|transverse]], [[Descending colon|descending]] and [[sigmoid colon]] have shown that IBS leads to altered [[Colon (anatomy)|colonic]] and [[Small intestine|small intestinal]] [[Motor coordination|motor]] function, such as increased frequency and irregularity of [[Lumen|luminal]] contractions.
**[[Muscle|Motor]] changes lead to symptoms of [[diarrhea]] and [[constipation]].<ref name="pmid8789897">{{cite journal |vauthors=Schmidt T, Hackelsberger N, Widmer R, Meisel C, Pfeiffer A, Kaess H |title=Ambulatory 24-hour jejunal motility in diarrhea-predominant irritable bowel syndrome |journal=Scand. J. Gastroenterol. |volume=31 |issue=6 |pages=581–9 |year=1996 |pmid=8789897 |doi= |url=}}</ref><ref name="pmid2865504">{{cite journal |vauthors=Kumar D, Wingate DL |title=The irritable bowel syndrome: a paroxysmal motor disorder |journal=Lancet |volume=2 |issue=8462 |pages=973–7 |year=1985 |pmid=2865504 |doi= |url=}}</ref><ref name="pmid11215731">{{cite journal |vauthors=Simrén M, Castedal M, Svedlund J, Abrahamsson H, Björnsson E |title=Abnormal propagation pattern of duodenal pressure waves in the irritable bowel syndrome (IBS) [correction of (IBD)] |journal=Dig. Dis. Sci. |volume=45 |issue=11 |pages=2151–61 |year=2000 |pmid=11215731 |doi= |url=}}</ref>
***[[Diarrhea]]-prone IBS patients have increased responses to [[ingestion]], [[Corticotropin-releasing hormone|CRH]] ([[Corticotropin-releasing hormone|corticotropin releasing hormone]]), [[Cholecystokinin|CCK]] ([[cholecystokinin]]), which increase the peak amplitude of high-amplitude propagating [[Contraction|contractions]] (HAPCs)  and lead to [[Abdominal pain|abdominal discomfort]] with accelerated transit through the [[Colon (anatomy)|colon]]. <ref name="pmid11374689">{{cite journal |vauthors=Chey WY, Jin HO, Lee MH, Sun SW, Lee KY |title=Colonic motility abnormality in patients with irritable bowel syndrome exhibiting abdominal pain and diarrhea |journal=Am. J. Gastroenterol. |volume=96 |issue=5 |pages=1499–506 |year=2001 |pmid=11374689 |doi=10.1111/j.1572-0241.2001.03804.x |url=}}</ref><ref name="pmid7379673">{{cite journal |vauthors=Whitehead WE, Engel BT, Schuster MM |title=Irritable bowel syndrome: physiological and psychological differences between diarrhea-predominant and constipation-predominant patients |journal=Dig. Dis. Sci. |volume=25 |issue=6 |pages=404–13 |year=1980 |pmid=7379673 |doi= |url=}}</ref><ref name="pmid9691924">{{cite journal |vauthors=Fukudo S, Nomura T, Hongo M |title=Impact of corticotropin-releasing hormone on gastrointestinal motility and adrenocorticotropic hormone in normal controls and patients with irritable bowel syndrome |journal=Gut |volume=42 |issue=6 |pages=845–9 |year=1998 |pmid=9691924 |pmc=1727153 |doi= |url=}}</ref><ref name="pmid18456567">{{cite journal |vauthors=Camilleri M, McKinzie S, Busciglio I, Low PA, Sweetser S, Burton D, Baxter K, Ryks M, Zinsmeister AR |title=Prospective study of motor, sensory, psychologic, and autonomic functions in patients with irritable bowel syndrome |journal=Clin. Gastroenterol. Hepatol. |volume=6 |issue=7 |pages=772–81 |year=2008 |pmid=18456567 |pmc=2495078 |doi=10.1016/j.cgh.2008.02.060 |url=}}</ref><ref name="pmid3569764">{{cite journal |vauthors=Kellow JE, Phillips SF |title=Altered small bowel motility in irritable bowel syndrome is correlated with symptoms |journal=Gastroenterology |volume=92 |issue=6 |pages=1885–93 |year=1987 |pmid=3569764 |doi= |url=}}</ref>
***[[Constipation]]-prone [[Irritable bowel syndrome|IBS]] patients show fewer high-amplitude propagating [[Contraction|contractions]] (HAPCs) as compared to [[diarrhea]] prone [[Irritable bowel syndrome|IBS]] patients, delayed transit through the [[Colon (anatomy)|colon]] and decreased [[motility]].
****Changes in the [[Muscle|motor]] function of the [[Colon (anatomy)|colon]] are responsible for producing the [[Gastrointestinal tract|gastrointestinal]] symptoms of [[Irritable bowel syndrome|IBS]] such as altered [[Intestine|bowel]] habits and [[abdominal pain]].<ref name="pmid18456567" />
**'''Visceral hypersensitivity:'''
***IBS is associated with a decreased threshold for perception of [[Viscus|visceral]] stimuli (i.e. [[Viscus|visceral]] [[hypersensitivity]])<ref name="pmid18456567" /><ref name="pmid21537962">{{cite journal |vauthors=Barbara G, Cremon C, De Giorgio R, Dothel G, Zecchi L, Bellacosa L, Carini G, Stanghellini V, Corinaldesi R |title=Mechanisms underlying visceral hypersensitivity in irritable bowel syndrome |journal=Curr Gastroenterol Rep |volume=13 |issue=4 |pages=308–15 |year=2011 |pmid=21537962 |doi=10.1007/s11894-011-0195-7 |url=}}</ref><ref name="pmid2323511">{{cite journal |vauthors=Whitehead WE, Holtkotter B, Enck P, Hoelzl R, Holmes KD, Anthony J, Shabsin HS, Schuster MM |title=Tolerance for rectosigmoid distention in irritable bowel syndrome |journal=Gastroenterology |volume=98 |issue=5 Pt 1 |pages=1187–92 |year=1990 |pmid=2323511 |doi= |url=}}</ref>
***[[Rectum|Rectal]] [[distension]] produces painful and non-painful sensations at lower volumes in [[Irritable bowel syndrome|IBS]] patients as compared to healthy controls, suggesting the presence of [[afferent]] pathway disturbances in [[Viscus|visceral]] [[Nerve|innervation]]<ref name="pmid7797041">{{cite journal |vauthors=Mertz H, Naliboff B, Munakata J, Niazi N, Mayer EA |title=Altered rectal perception is a biological marker of patients with irritable bowel syndrome |journal=Gastroenterology |volume=109 |issue=1 |pages=40–52 |year=1995 |pmid=7797041 |doi= |url=}}</ref><ref name="pmid2338274">{{cite journal |vauthors=Prior A, Maxton DG, Whorwell PJ |title=Anorectal manometry in irritable bowel syndrome: differences between diarrhoea and constipation predominant subjects |journal=Gut |volume=31 |issue=4 |pages=458–62 |year=1990 |pmid=2338274 |pmc=1378424 |doi= |url=}}</ref><ref name="pmid17919487">{{cite journal |vauthors=Posserud I, Syrous A, Lindström L, Tack J, Abrahamsson H, Simrén M |title=Altered rectal perception in irritable bowel syndrome is associated with symptom severity |journal=Gastroenterology |volume=133 |issue=4 |pages=1113–23 |year=2007 |pmid=17919487 |doi=10.1053/j.gastro.2007.07.024 |url=}}</ref><ref name="pmid12055583">{{cite journal |vauthors=Bouin M, Plourde V, Boivin M, Riberdy M, Lupien F, Laganière M, Verrier P, Poitras P |title=Rectal distention testing in patients with irritable bowel syndrome: sensitivity, specificity, and predictive values of pain sensory thresholds |journal=Gastroenterology |volume=122 |issue=7 |pages=1771–7 |year=2002 |pmid=12055583 |doi= |url=}}</ref>.
***[[Viscus|Visceral]] [[hypersensitivity]] contributes to [[Irritable bowel syndrome|IBS]] by involving the following:
****'''[[Spinal cord|Spinal]] hyperexcitability'''
*****Secondary to activation of  [[Neurotransmitter|neurotransmitters]] such as:
*****[[NMDA receptor|N-methyl D aspartate (NMDA) receptor]]
*****[[Nitric oxide]] 
****'''Activation of specific [[Gastrointestinal tract|gastrointestinal]] mediators''' that lead to [[Afferent nerve|afferent]] [[nerve]] fiber sensitization:
*****[[Kinins]] 
*****[[Serotonin]] 
****'''Central ([[Brain stem|brainstem]] and [[Cerebral cortex|cortical]]) modulation''' with increased activation of anterior [[cingulate cortex]], [[thalamus]] and [[Insular cortex|insula]].
*****These structures are involved in processing of pain. 
*****[[Cortical area|Cortical]] and [[brain stem]] modulation translate into long term hypersensitivity due to [[neuroplasticity]].
*****Semi permanent changes(seen on functional [[magnetic resonance imaging]] and [[positron emission tomography]])  in the [[Nervous system|neural]] response to [[Viscus|visceral]] stimulation contribute to [[Viscus|visceral]] [[hypersensitivity]].''<ref name="pmid21537962" /><ref name="pmid10784583">{{cite journal |vauthors=Mertz H, Morgan V, Tanner G, Pickens D, Price R, Shyr Y, Kessler R |title=Regional cerebral activation in irritable bowel syndrome and control subjects with painful and nonpainful rectal distention |journal=Gastroenterology |volume=118 |issue=5 |pages=842–8 |year=2000 |pmid=10784583 |doi= |url=}}</ref>  ''
****'''Recruitment of peripheral silent [[Nociceptor|nociceptors]]''' cause increased end [[Organ (anatomy)|organ]] sensitivity due to
*****[[Hormone|Hormonal]] activation ( increased [[serotonin]] affects [[Gastrointestinal tract|gastrointestinal]] [[motility]] and [[Viscus|visceral]] [[pain]] perception)
*****[[Immunity (medical)|Immune]] activation(recruitment of [[Inflammation|inflammatory]] mediators)<ref name="pmid21537962" />
{{familytree/start |summary=PE diagnosis Algorithm.}}
{{familytree | | | | | | | | | |,|-| A01 |-| A02 | | | |A01=[[Spinal cord|Spinal]] hyperexcitability |A02= Activation of <br>• [[NMDA receptor|N-methyl D aspartate (NMDA) receptor]] <br>• [[nitric oxide]] }}
{{familytree | | | | | | | | | |!| | | | | | | | | | | | | | | | | | }}
{{familytree | | | | | | | | | |)|-| B01 |-| B02 | | | |B01=Central ([[Brain stem|brainstem]] and [[Cerebral cortex|cortical]]) modulation |B02=Increased activation of: <br>• Anterior [[cingulate cortex]] <br>• [[Thalamus]] <br>• [[Insular cortex|insula]] <br> }}
{{familytree | | | | | | C01 |-|(| | | | | | | | | | | | | | | | | |C01='''[[Visceral]] [[hypersensitivity]]''' }}
{{familytree | | | | | | | | | |)|-| C02 |-| C03 | | | |C02=Activation of specific [[gastrointestinal]] [[mediators]] |C03=[[Kinins]] and [[serotonin]] activation lead to [[afferent nerve]] fiber sensitization  }}
{{familytree | | | | | | | | | |!| | | | | | | | | | | | | | | | | | }}
{{familytree | | | | | | | | | |`|-| D01 |-| D02 | | | |D01=Recruitment of [[peripheral]] silent [[nociceptors]] |D02=Increased [[end]] [[organ]] sensitivity due to [[hormonal]] or [[immune]] activation }}


From the late 1990s, research publications began identifying specific biochemical changes present in tissue biopsies and serum samples from IBS patients that suggested symptoms had an organic rather than [[psychosomatic]] cause.  These studies identified [[cytokine]]s and secretory products in tissues taken from IBS patients.  The cytokines identified in IBS patients produce [[inflammation]] and are associated with the body's [[Immunity (medical)|immune]] response.


* A study showed that intestinal [[biopsies]] from patients with constipation predominant IBS secreted higher levels of [[serotonin]] in-vitro.<ref>{{cite journal |author=Miwa J, Echizen H, Matsueda K, Umeda N |title=Patients with constipation-predominant irritable bowel syndrome (IBS) may have elevated serotonin concentrations in colonic mucosa as compared with diarrhea-predominant patients and subjects with normal bowel habits |journal=Digestion |volume=63 |issue=3 |pages=188-94|year=2001 |pmid=11351146 |doi=}}</ref>  [[Serotonin]] plays a role in regulating gastrointestinal motility and water content and can be altered by some diseases and infections.<ref name="MCGOWAN_1983"> {{cite journal |author=McGowan K, Kane A, Asarkof N, ''et al'' |title=Entamoeba histolytica causes intestinal secretion: role of serotonin |journal=Science |volume=221 |issue=4612|pages=762-4 |year=1983 |pmid=6308760 |doi=}} </ref><ref name="MCGOWAN_1985"> {{cite journal |author=McGowan K, Guerina V, Wicks J, Donowitz M |title=Secretory hormones of Entamoeba histolytica |journal=Ciba Found. Symp. |volume=112 |issue= |pages=139-54|year=1985 |pmid=2861068 |doi=}} </ref><ref>{{cite journal |author=Banu, Naheed, et al. |title=Neurohumoral alterations and their role in amoebiasis. |journal=Indian J. Clin Biochem |volume=20 |issue=2 |pages=142-5 |year=2005|url=http://medind.nic.in/iaf/t05/i2/iaft05i2p142.pdf}}</ref>
{{familytree/end}}
<br><br><br>
*'''[[Immune]] activation and [[mucosal]] [[inflammation]]'''{{Family tree/start}}
{{Family tree | A01 |-|-| A02 |-|-|-| A03 | |A01= '''[[Mast cells]]'''| A02= '''[[IMMUNE]] ACTIVATION AND [[MUCOSAL]] [[INFLAMMATION]]'''| A03='''[[Lymphocytes]]'''}}


* A study of rectal biopsy tissue from IBS patients showed increased levels of cellular structures involved in the production of the cytokine [[Interleukin 1]] Beta.<ref>{{cite journal |author=Gwee KA, Collins SM, Read NW, ''et al'' |title=Increased rectal mucosal expression of interleukin 1beta in recently acquired post-infectious irritable bowel syndrome |journal=Gut |volume=52 |issue=4|pages=523-6 |year=2003 |pmid=12631663 |doi=}}</ref>


* A study of blood samples from IBS patients identified elevated levels of cytokines [[Tumor necrosis factor-alpha]], [[Interleukin 1]], and [[Interleukin 6]] in patients with IBS.<ref name="pmid17383420">{{cite journal |author=Liebregts T, Adam B, Bredack C, ''et al'' |title=Immune activation in patients with irritable bowel syndrome |journal=Gastroenterology |volume=132 |issue=3 |pages=913-20|year=2007 |pmid=17383420 |doi=10.1053/j.gastro.2007.01.046}}</ref>
{{Family tree | | | | | | |!| | | | | }}
{{Family tree | | | | | | |!| | | | | }}
{{Family tree | | | | | | B01 | | | |B01= '''[[Proinflammatory]] [[cytokines]]'''}}
{{Family tree/end}}
*IBS in patients with history of [[inflammatory bowel disease]], [[celiac disease]] or [[microscopic colitis]] points towards the fact that [[Immunity (medical)|immune]] activation and local [[Gastrointestinal tract|GI]] [[Mucous membrane|mucosal]] [[inflammation]] play an important role in its [[pathogenesis]].<ref name="pmid19997094">{{cite journal |vauthors=Coëffier M, Gloro R, Boukhettala N, Aziz M, Lecleire S, Vandaele N, Antonietti M, Savoye G, Bôle-Feysot C, Déchelotte P, Reimund JM, Ducrotté P |title=Increased proteasome-mediated degradation of occludin in irritable bowel syndrome |journal=Am. J. Gastroenterol. |volume=105 |issue=5 |pages=1181–8 |year=2010 |pmid=19997094 |doi=10.1038/ajg.2009.700 |url=}}</ref><ref name="pmid12055584">{{cite journal |vauthors=Chadwick VS, Chen W, Shu D, Paulus B, Bethwaite P, Tie A, Wilson I |title=Activation of the mucosal immune system in irritable bowel syndrome |journal=Gastroenterology |volume=122 |issue=7 |pages=1778–83 |year=2002 |pmid=12055584 |doi= |url=}}</ref><ref name="pmid17383420">{{cite journal |vauthors=Liebregts T, Adam B, Bredack C, Röth A, Heinzel S, Lester S, Downie-Doyle S, Smith E, Drew P, Talley NJ, Holtmann G |title=Immune activation in patients with irritable bowel syndrome |journal=Gastroenterology |volume=132 |issue=3 |pages=913–20 |year=2007 |pmid=17383420 |doi=10.1053/j.gastro.2007.01.046 |url=}}</ref><ref name="pmid12454854">{{cite journal |vauthors=Törnblom H, Lindberg G, Nyberg B, Veress B |title=Full-thickness biopsy of the jejunum reveals inflammation and enteric neuropathy in irritable bowel syndrome |journal=Gastroenterology |volume=123 |issue=6 |pages=1972–9 |year=2002 |pmid=12454854 |doi=10.1053/gast.2002.37059 |url=}}</ref><ref name="pmid17005763">{{cite journal |vauthors=Guilarte M, Santos J, de Torres I, Alonso C, Vicario M, Ramos L, Martínez C, Casellas F, Saperas E, Malagelada JR |title=Diarrhoea-predominant IBS patients show mast cell activation and hyperplasia in the jejunum |journal=Gut |volume=56 |issue=2 |pages=203–9 |year=2007 |pmid=17005763 |pmc=1856785 |doi=10.1136/gut.2006.100594 |url=}}</ref><ref name="pmid14988823">{{cite journal |vauthors=Barbara G, Stanghellini V, De Giorgio R, Cremon C, Cottrell GS, Santini D, Pasquinelli G, Morselli-Labate AM, Grady EF, Bunnett NW, Collins SM, Corinaldesi R |title=Activated mast cells in proximity to colonic nerves correlate with abdominal pain in irritable bowel syndrome |journal=Gastroenterology |volume=126 |issue=3 |pages=693–702 |year=2004 |pmid=14988823 |doi= |url=}}</ref><ref name="pmid17383420" />
* IBS patients have higher [[Mucous membrane|mucosal]] counts of ''[[Lymphocyte|lymphocytes]]'' (T cells, B cells), ''[[Mast cell|mast]] cells'' and immune ''mediators'' such as prostanoids, [[Protease|proteases]], [[Cytokine|cytokines]] and [[Histamine|histamines]].<ref name="pmid17383420" /><ref name="pmid20427395">{{cite journal |vauthors=Marshall JK, Thabane M, Garg AX, Clark WF, Moayyedi P, Collins SM |title=Eight year prognosis of postinfectious irritable bowel syndrome following waterborne bacterial dysentery |journal=Gut |volume=59 |issue=5 |pages=605–11 |year=2010 |pmid=20427395 |doi=10.1136/gut.2009.202234 |url=}}</ref><ref name="pmid21911849">{{cite journal |vauthors=Wensaas KA, Langeland N, Hanevik K, Mørch K, Eide GE, Rortveit G |title=Irritable bowel syndrome and chronic fatigue 3 years after acute giardiasis: historic cohort study |journal=Gut |volume=61 |issue=2 |pages=214–9 |year=2012 |pmid=21911849 |doi=10.1136/gutjnl-2011-300220 |url=}}</ref><ref name="pmid19711225">{{cite journal |vauthors=Mearin F, Perelló A, Balboa A, Perona M, Sans M, Salas A, Angulo S, Lloreta J, Benasayag R, García-Gonzalez MA, Pérez-Oliveras M, Coderch J |title=Pathogenic mechanisms of postinfectious functional gastrointestinal disorders: results 3 years after gastroenteritis |journal=Scand. J. Gastroenterol. |volume=44 |issue=10 |pages=1173–85 |year=2009 |pmid=19711225 |doi=10.1080/00365520903171276 |url=}}</ref><ref name="pmid12631663">{{cite journal |vauthors=Gwee KA, Collins SM, Read NW, Rajnakova A, Deng Y, Graham JC, McKendrick MW, Moochhala SM |title=Increased rectal mucosal expression of interleukin 1beta in recently acquired post-infectious irritable bowel syndrome |journal=Gut |volume=52 |issue=4 |pages=523–6 |year=2003 |pmid=12631663 |pmc=1773606 |doi= |url=}}</ref>
** '''Lymphocytes:'''
***Activation of [[humoral immunity]] in [[Irritable bowel syndrome|IBS]] is specific for the [[gastrointestinal tract]]. Increased number of [[Lymphocyte|lymphocytes]] have been found in the [[small intestine]] and [[Colon (anatomy)|colon]] of [[Irritable bowel syndrome|IBS]] patients.<ref name="pmid12055584" /><ref name="pmid12454854" /><ref name="pmid19222763">{{cite journal |vauthors=Ohman L, Lindmark AC, Isaksson S, Posserud I, Strid H, Sjövall H, Simrén M |title=B-cell activation in patients with irritable bowel syndrome (IBS) |journal=Neurogastroenterol. Motil. |volume=21 |issue=6 |pages=644–50, e27 |year=2009 |pmid=19222763 |doi=10.1111/j.1365-2982.2009.01272.x |url=}}</ref><ref name="pmid25209656">{{cite journal |vauthors=Vicario M, González-Castro AM, Martínez C, Lobo B, Pigrau M, Guilarte M, de Torres I, Mosquera JL, Fortea M, Sevillano-Aguilera C, Salvo-Romero E, Alonso C, Rodiño-Janeiro BK, Söderholm JD, Azpiroz F, Santos J |title=Increased humoral immunity in the jejunum of diarrhoea-predominant irritable bowel syndrome associated with clinical manifestations |journal=Gut |volume=64 |issue=9 |pages=1379–88 |year=2015 |pmid=25209656 |doi=10.1136/gutjnl-2013-306236 |url=}}</ref>
***[[Irritable bowel syndrome|IBS]] patients with [[diarrhea]] have enhanced [[Mucous membrane|mucosal]] [[Humoral immunity|humoral]] activity, associated with activation and [[Cell growth|proliferation]] of [[B cell|B cells]] and [[Antibody|immunoglobulin]] production, identified by microarray profiling.<ref name="pmid25209656" />
***[[Irritable bowel syndrome|IBS]] patients with severe disease have an increase in [[lymphocyte]] [[Infiltration (medical)|infiltration]] in the myentric plexus.<ref name="pmid12454854" />
***Mediators released by [[Lymphocyte|lymphocytes]] include [[histamine]], [[Protease|proteases]] and [[nitric oxide]]. The stimulation of the [[enteric nervous system]] by these mediators leads to abnormal [[Viscus|visceral]] and [[Muscle|motor]] responses within the [[gastrointestinal tract]].<ref name="pmid12055584" />
***Stool in patients with [[diarrhea]] prominent [[Irritable bowel syndrome|IBS]] demonstrates high levels of [[serine]] [[protease]] activity, which is produced by [[Lymphocyte|lymphocytes]].<ref name="pmid18924448">{{cite journal |vauthors=Bueno L |title=Protease activated receptor 2: a new target for IBS treatment |journal=Eur Rev Med Pharmacol Sci |volume=12 Suppl 1 |issue= |pages=95–102 |year=2008 |pmid=18924448 |doi= |url=}}</ref><ref name="pmid18194983">{{cite journal |vauthors=Gecse K, Róka R, Ferrier L, Leveque M, Eutamene H, Cartier C, Ait-Belgnaoui A, Rosztóczy A, Izbéki F, Fioramonti J, Wittmann T, Bueno L |title=Increased faecal serine protease activity in diarrhoeic IBS patients: a colonic lumenal factor impairing colonic permeability and sensitivity |journal=Gut |volume=57 |issue=5 |pages=591–9 |year=2008 |pmid=18194983 |doi=10.1136/gut.2007.140210 |url=}}</ref>
***In response to high levels of [[serine protease]], there is increased [[Viscus|visceral]] pain and [[Colon (anatomy)|colonic]] cellular permeability. <ref name="pmid18924448" />
***[[Serine protease]] inhibitors prevent effects mediated by high levels of [[serine protease]] in [[Irritable bowel syndrome|IBS]] patients.<ref name="pmid18194983" /><ref name="pmid18924448" />
**'''Mast cells:'''
***  [[Irritable bowel syndrome|IBS]] leads to an increased number of [[Mast cell|mast cells]] in [[Irritable bowel syndrome|IBS]] patients in the [[jejunum]], [[terminal ileum]] and [[Colon (anatomy)|colon]].<ref name="pmid14988823" />
*** Higher numbers of activated [[Mast cell|mast cells]] are found in proximity to [[Colon (anatomy)|colonic]] nerve fibres in the mucosa of the [[Gastrointestinal tract|gastrointestinal]] [[tract]] of [[Irritable bowel syndrome|IBS]] patients. <ref name="pmid14988823" /><ref name="pmid17005763" />
** '''Proinflammatory cytokines:'''
*** [[Cytokine|Cytokines]] are protein mediators of the [[Immunity (medical)|immune]] response. Increased levels of [[Cytokine|cytokines]] have been found in [[Irritable bowel syndrome|IBS]] patients.<ref name="pmid19711225" /><ref name="pmid12631663" />
*** Higher amounts of [[Tumour necrosis factor|tumor necrosis factor]] are produced by the peripheral blood [[Monocyte|mononuclear]] cells of [[Irritable bowel syndrome|IBS]] patients.<ref name="pmid17383420" /><ref name="pmid16472586">{{cite journal |vauthors=Dinan TG, Quigley EM, Ahmed SM, Scully P, O'Brien S, O'Mahony L, O'Mahony S, Shanahan F, Keeling PW |title=Hypothalamic-pituitary-gut axis dysregulation in irritable bowel syndrome: plasma cytokines as a potential biomarker? |journal=Gastroenterology |volume=130 |issue=2 |pages=304–11 |year=2006 |pmid=16472586 |doi=10.1053/j.gastro.2005.11.033 |url=}}</ref>
*** Other [[Cytokine|cytokines]] such as [[Interleukin|interleukin 1β]], [[interleukin]] 6, [[Interleukin 10|interleukin10]], and [[Tumor necrosis factor-alpha|TNFα]] are raised in [[Irritable bowel syndrome|IBS]] patients.
*** Increased concentration of [[Cytokine|cytokines]] is directly proportional to the severity and frequency of pain.<ref name="pmid17383420" /><ref name="pmid16472586" /><ref name="pmid25063707" />
*** The [[Tumor necrosis factors|TNF]] [[antagonist]] [[infliximab]] counteracts pain in [[Irritable bowel syndrome|IBS]] patients, proving [[Tumor necrosis factors|TNF]] involvement in mechanical [[hypersensitivity]] of the [[Colon (anatomy)|colonic]] [[afferent nerve]] endings.<ref name="pmid25063707">{{cite journal |vauthors=Hughes PA, Moretta M, Lim A, Grasby DJ, Bird D, Brierley SM, Liebregts T, Adam B, Blackshaw LA, Holtmann G, Bampton P, Hoffmann P, Andrews JM, Zola H, Krumbiegel D |title=Immune derived opioidergic inhibition of viscerosensory afferents is decreased in Irritable Bowel Syndrome patients |journal=Brain Behav. Immun. |volume=42 |issue= |pages=191–203 |year=2014 |pmid=25063707 |doi=10.1016/j.bbi.2014.07.001 |url=}}</ref>
* '''Altered gut microbiota'''
** [[Gut flora|Fecal microflora]] in [[Irritable bowel syndrome|IBS]] patients differ from healthy individuals. Some IBS patients have [[Colon (anatomy)|colonic]] [[Spirochaete|spirochaetosis]], with a unique pathology of increased [[Lymphatic system|lymphoid]] follicles and [[Eosinophil granulocyte|eosinophils]] on [[histology]].<ref name="pmid20427395" /><ref name="pmid25540866">{{cite journal |vauthors=Walker MM, Talley NJ, Inganäs L, Engstrand L, Jones MP, Nyhlin H, Agréus L, Kjellstrom L, Öst Å, Andreasson A |title=Colonic spirochetosis is associated with colonic eosinophilia and irritable bowel syndrome in a general population in Sweden |journal=Hum. Pathol. |volume=46 |issue=2 |pages=277–83 |year=2015 |pmid=25540866 |doi=10.1016/j.humpath.2014.10.026 |url=}}</ref><ref name="pmid17631127">{{cite journal |vauthors=Kassinen A, Krogius-Kurikka L, Mäkivuokko H, Rinttilä T, Paulin L, Corander J, Malinen E, Apajalahti J, Palva A |title=The fecal microbiota of irritable bowel syndrome patients differs significantly from that of healthy subjects |journal=Gastroenterology |volume=133 |issue=1 |pages=24–33 |year=2007 |pmid=17631127 |doi=10.1053/j.gastro.2007.04.005 |url=}}</ref><ref name="pmid15667495">{{cite journal |vauthors=Malinen E, Rinttilä T, Kajander K, Mättö J, Kassinen A, Krogius L, Saarela M, Korpela R, Palva A |title=Analysis of the fecal microbiota of irritable bowel syndrome patients and healthy controls with real-time PCR |journal=Am. J. Gastroenterol. |volume=100 |issue=2 |pages=373–82 |year=2005 |pmid=15667495 |doi=10.1111/j.1572-0241.2005.40312.x |url=}}</ref><ref name="pmid21820992">{{cite journal |vauthors=Rajilić-Stojanović M, Biagi E, Heilig HG, Kajander K, Kekkonen RA, Tims S, de Vos WM |title=Global and deep molecular analysis of microbiota signatures in fecal samples from patients with irritable bowel syndrome |journal=Gastroenterology |volume=141 |issue=5 |pages=1792–801 |year=2011 |pmid=21820992 |doi=10.1053/j.gastro.2011.07.043 |url=}}</ref><ref name="pmid21741921">{{cite journal |vauthors=Saulnier DM, Riehle K, Mistretta TA, Diaz MA, Mandal D, Raza S, Weidler EM, Qin X, Coarfa C, Milosavljevic A, Petrosino JF, Highlander S, Gibbs R, Lynch SV, Shulman RJ, Versalovic J |title=Gastrointestinal microbiome signatures of pediatric patients with irritable bowel syndrome |journal=Gastroenterology |volume=141 |issue=5 |pages=1782–91 |year=2011 |pmid=21741921 |pmc=3417828 |doi=10.1053/j.gastro.2011.06.072 |url=}}</ref><ref name="pmid22180058">{{cite journal |vauthors=Jeffery IB, O'Toole PW, Öhman L, Claesson MJ, Deane J, Quigley EM, Simrén M |title=An irritable bowel syndrome subtype defined by species-specific alterations in faecal microbiota |journal=Gut |volume=61 |issue=7 |pages=997–1006 |year=2012 |pmid=22180058 |doi=10.1136/gutjnl-2011-301501 |url=}}</ref><ref name="pmid20117111">{{cite journal |vauthors=Ford AC, Thabane M, Collins SM, Moayyedi P, Garg AX, Clark WF, Marshall JK |title=Prevalence of uninvestigated dyspepsia 8 years after a large waterborne outbreak of bacterial dysentery: a cohort study |journal=Gastroenterology |volume=138 |issue=5 |pages=1727–36; quiz e12 |year=2010 |pmid=20117111 |doi=10.1053/j.gastro.2010.01.043 |url=}}</ref>
** Acute [[Gastrointestinal tract|GI]] [[infection]] alters [[Gut flora|gut microflora]] switches on a [[T helper cell|T-helper-2]] [[Immunity (medical)|immune]]-cell response with increased numbers of [[CD8]] and CD4RA-positive [[Intraepithelial lymphocyte|intraepithelial]] [[Lymphocyte|lymphocytes]], causing increased susceptibility to the development of [[Irritable bowel syndrome|IBS]].  <ref name="pmid25521822">{{cite journal |vauthors=Sundin J, Rangel I, Fuentes S, Heikamp-de Jong I, Hultgren-Hörnquist E, de Vos WM, Brummer RJ |title=Altered faecal and mucosal microbial composition in post-infectious irritable bowel syndrome patients correlates with mucosal lymphocyte phenotypes and psychological distress |journal=Aliment. Pharmacol. Ther. |volume=41 |issue=4 |pages=342–51 |year=2015 |pmid=25521822 |doi=10.1111/apt.13055 |url=}}</ref><ref name="pmid26071133">{{cite journal |vauthors=Wouters MM, Van Wanrooy S, Nguyen A, Dooley J, Aguilera-Lizarraga J, Van Brabant W, Garcia-Perez JE, Van Oudenhove L, Van Ranst M, Verhaegen J, Liston A, Boeckxstaens G |title=Psychological comorbidity increases the risk for postinfectious IBS partly by enhanced susceptibility to develop infectious gastroenteritis |journal=Gut |volume=65 |issue=8 |pages=1279–88 |year=2016 |pmid=26071133 |doi=10.1136/gutjnl-2015-309460 |url=}}</ref><ref name="pmid26729548">{{cite journal |vauthors=Riddle MS, Welsh M, Porter CK, Nieh C, Boyko EJ, Gackstetter G, Hooper TI |title=The Epidemiology of Irritable Bowel Syndrome in the US Military: Findings from the Millennium Cohort Study |journal=Am. J. Gastroenterol. |volume=111 |issue=1 |pages=93–104 |year=2016 |pmid=26729548 |pmc=4759150 |doi=10.1038/ajg.2015.386 |url=}}</ref>
** Altered [[Gut flora|gut microbiota]] causes increased [[Colon (anatomy)|colonic]] [[hypersensitivity]]. <ref name="pmid23433203">{{cite journal |vauthors=Crouzet L, Gaultier E, Del'Homme C, Cartier C, Delmas E, Dapoigny M, Fioramonti J, Bernalier-Donadille A |title=The hypersensitivity to colonic distension of IBS patients can be transferred to rats through their fecal microbiota |journal=Neurogastroenterol. Motil. |volume=25 |issue=4 |pages=e272–82 |year=2013 |pmid=23433203 |doi=10.1111/nmo.12103 |url=}}</ref>
* '''Abnormal serotonin pathways'''
** [[Serotonin]](5-HT) is an important [[neurotransmitter]] produced by the [[Enterochromaffin cell|enterochromaffin cells]] in the [[Colon (anatomy)|colon]], in response to [[Chemical substance|chemical]] stimuli ([[Short chain fatty acid|short chain fatty acids]] produced by [[Gut flora|gastrointestinal microflora]] ) and mechanical [[Stimulus (physiology)|stimuli]] ( food) and is increased in [[Irritable bowel syndrome|IBS]] patients.<ref name="pmid14724817">{{cite journal |vauthors=Dunlop SP, Jenkins D, Neal KR, Spiller RC |title=Relative importance of enterochromaffin cell hyperplasia, anxiety, and depression in postinfectious IBS |journal=Gastroenterology |volume=125 |issue=6 |pages=1651–9 |year=2003 |pmid=14724817 |doi= |url=}}</ref><ref name="pmid2078274">{{cite journal |vauthors=Gershon MD, Wade PR, Kirchgessner AL, Tamir H |title=5-HT receptor subtypes outside the central nervous system. Roles in the physiology of the gut |journal=Neuropsychopharmacology |volume=3 |issue=5-6 |pages=385–95 |year=1990 |pmid=2078274 |doi= |url=}}</ref><ref name="pmid19630576">{{cite journal |vauthors=Berger M, Gray JA, Roth BL |title=The expanded biology of serotonin |journal=Annu. Rev. Med. |volume=60 |issue= |pages=355–66 |year=2009 |pmid=19630576 |doi=10.1146/annurev.med.60.042307.110802 |url=}}</ref><ref name="pmid15822040">{{cite journal |vauthors=Dunlop SP, Coleman NS, Blackshaw E, Perkins AC, Singh G, Marsden CA, Spiller RC |title=Abnormalities of 5-hydroxytryptamine metabolism in irritable bowel syndrome |journal=Clin. Gastroenterol. Hepatol. |volume=3 |issue=4 |pages=349–57 |year=2005 |pmid=15822040 |doi= |url=}}</ref><ref name="pmid16401466">{{cite journal |vauthors=Atkinson W, Lockhart S, Whorwell PJ, Keevil B, Houghton LA |title=Altered 5-hydroxytryptamine signaling in patients with constipation- and diarrhea-predominant irritable bowel syndrome |journal=Gastroenterology |volume=130 |issue=1 |pages=34–43 |year=2006 |pmid=16401466 |doi=10.1053/j.gastro.2005.09.031 |url=}}</ref><ref name="pmid23222853">{{cite journal |vauthors=Gershon MD |title=5-Hydroxytryptamine (serotonin) in the gastrointestinal tract |journal=Curr Opin Endocrinol Diabetes Obes |volume=20 |issue=1 |pages=14–21 |year=2013 |pmid=23222853 |pmc=3708472 |doi=10.1097/MED.0b013e32835bc703 |url=}}</ref><ref name="pmid23872499">{{cite journal |vauthors=Shekhar C, Monaghan PJ, Morris J, Issa B, Whorwell PJ, Keevil B, Houghton LA |title=Rome III functional constipation and irritable bowel syndrome with constipation are similar disorders within a spectrum of sensitization, regulated by serotonin |journal=Gastroenterology |volume=145 |issue=4 |pages=749–57; quiz e13–4 |year=2013 |pmid=23872499 |doi=10.1053/j.gastro.2013.07.014 |url=}}</ref> 
** [[Serotonin]] affects [[Gastrointestinal tract|gastrointestinal]] [[motility]] and [[Viscus|visceral]] pain perception. Spontaneous release of 5-[[Serotonin|HT]] correlates with [[abdominal pain]] severity.<ref name="pmid21427712">{{cite journal |vauthors=Cremon C, Carini G, Wang B, Vasina V, Cogliandro RF, De Giorgio R, Stanghellini V, Grundy D, Tonini M, De Ponti F, Corinaldesi R, Barbara G |title=Intestinal serotonin release, sensory neuron activation, and abdominal pain in irritable bowel syndrome |journal=Am. J. Gastroenterol. |volume=106 |issue=7 |pages=1290–8 |year=2011 |pmid=21427712 |doi=10.1038/ajg.2011.86 |url=}}</ref> 
** There is an established relationship between [[Irritable bowel syndrome|IBS]] and [[polymorphisms]] in the gene for [[serotonin]] transport causing alteration in [[Intestine|intestinal]] [[peristalsis]] due to change in the [[serotonin]] reuptake efficacy.<ref name="pmid24060757">{{cite journal |vauthors=Grasberger H, Chang L, Shih W, Presson AP, Sayuk GS, Newberry RD, Karagiannides I, Pothoulakis C, Mayer E, Merchant JL |title=Identification of a functional TPH1 polymorphism associated with irritable bowel syndrome bowel habit subtypes |journal=Am. J. Gastroenterol. |volume=108 |issue=11 |pages=1766–74 |year=2013 |pmid=24060757 |pmc=4067697 |doi=10.1038/ajg.2013.304 |url=}}</ref><ref name="pmid21073637">{{cite journal |vauthors=Jun S, Kohen R, Cain KC, Jarrett ME, Heitkemper MM |title=Associations of tryptophan hydroxylase gene polymorphisms with irritable bowel syndrome |journal=Neurogastroenterol. Motil. |volume=23 |issue=3 |pages=233–9, e116 |year=2011 |pmid=21073637 |pmc=3057463 |doi=10.1111/j.1365-2982.2010.01623.x |url=}}</ref><ref name="pmid15138209">{{cite journal |vauthors=Kim HJ, Camilleri M, Carlson PJ, Cremonini F, Ferber I, Stephens D, McKinzie S, Zinsmeister AR, Urrutia R |title=Association of distinct alpha(2) adrenoceptor and serotonin transporter polymorphisms with constipation and somatic symptoms in functional gastrointestinal disorders |journal=Gut |volume=53 |issue=6 |pages=829–37 |year=2004 |pmid=15138209 |pmc=1774073 |doi= |url=}}</ref><ref name="pmid15361494">{{cite journal |vauthors=Yeo A, Boyd P, Lumsden S, Saunders T, Handley A, Stubbins M, Knaggs A, Asquith S, Taylor I, Bahari B, Crocker N, Rallan R, Varsani S, Montgomery D, Alpers DH, Dukes GE, Purvis I, Hicks GA |title=Association between a functional polymorphism in the serotonin transporter gene and diarrhoea predominant irritable bowel syndrome in women |journal=Gut |volume=53 |issue=10 |pages=1452–8 |year=2004 |pmid=15361494 |pmc=1774243 |doi=10.1136/gut.2003.035451 |url=}}</ref> 
** Increased [[serotonin]] production contributes to [[postprandial]] symptoms in [[Irritable bowel syndrome|IBS]] patients, hence providing the rationale for the therapeutic efficacy of 5-HT 3 receptor [[Receptor antagonist|antagonists]] and 5-HT 4 receptor [[Agonist|agonists]] on symptoms in [[Irritable bowel syndrome|IBS]] patients.<ref name="pmid17241888">{{cite journal |vauthors=Gershon MD, Tack J |title=The serotonin signaling system: from basic understanding to drug development for functional GI disorders |journal=Gastroenterology |volume=132 |issue=1 |pages=397–414 |year=2007 |pmid=17241888 |doi=10.1053/j.gastro.2006.11.002 |url=}}</ref><ref name="pmid22071696">{{cite journal |vauthors=Camilleri M |title=Pharmacology of the new treatments for lower gastrointestinal motility disorders and irritable bowel syndrome |journal=Clin. Pharmacol. Ther. |volume=91 |issue=1 |pages=44–59 |year=2012 |pmid=22071696 |doi=10.1038/clpt.2011.261 |url=}}</ref>


* A study of intestinal biopsies from IBS patients showed increased levels of [[protease]] enzymes used by the body to digest proteins, and by infectious agents to combat the host's [[immune system]].<ref>{{cite journal |author=Cenac N, Andrews CN, Holzhausen M, ''et al'' |title=Role for protease activity in visceral pain in irritable bowel syndrome |journal=J. Clin. Invest.|volume=117 |issue=3 |pages=636-47 |year=2007 |pmid=17304351 |doi=10.1172/JCI29255}}</ref>
==='''Psychosocial factors and CNS dysregulation'''===
* [[Symptom]] exacerbation occurs in [[Irritable bowel syndrome|IBS]] patients with emotional disturbances,[[Stress (medicine)|stress]], [[anxiety]] or [[depression]]. Traumatic experiences before 18 years of age directly shape adult connectivity in the executive control network consisting of structures such as the [[Insular cortex|insula]], anterior [[cingulate cortex]] and the [[thalamus]].
* Semipermanent/permanent changes in complex [[Nervous system|neural]] circuits lead to central pain amplification and contribute to [[abdominal pain]] in IBS patients.<ref name="pmid27061107">{{cite journal |vauthors=Park SH, Videlock EJ, Shih W, Presson AP, Mayer EA, Chang L |title=Adverse childhood experiences are associated with irritable bowel syndrome and gastrointestinal symptom severity |journal=Neurogastroenterol. Motil. |volume=28 |issue=8 |pages=1252–60 |year=2016 |pmid=27061107 |pmc=4956522 |doi=10.1111/nmo.12826 |url=}}</ref><ref name="pmid25003944">{{cite journal |vauthors=Gupta A, Kilpatrick L, Labus J, Tillisch K, Braun A, Hong JY, Ashe-McNalley C, Naliboff B, Mayer EA |title=Early adverse life events and resting state neural networks in patients with chronic abdominal pain: evidence for sex differences |journal=Psychosom Med |volume=76 |issue=6 |pages=404–12 |year=2014 |pmid=25003944 |pmc=4113723 |doi=10.1097/PSY.0000000000000089 |url=}}</ref>
* The dorsolateral [[prefrontal cortex]] activity (responsible for vigilance and alertness of the human brain) and the mid-[[Cingulate cortex|cingulate corte]]<nowiki/>x (engaged in attention pathways and responses) is reduced in [[Irritable bowel syndrome|IBS]] patients, seen on advanced brain imaging techniques as irregularities in the mid- [[cingulate cortex]] and [[prefrontal cortex]] on [[Diffusion MRI|diffusion tensor imaging]]. <ref name="pmid23864686">{{cite journal |vauthors=Hong JY, Kilpatrick LA, Labus J, Gupta A, Jiang Z, Ashe-McNalley C, Stains J, Heendeniya N, Ebrat B, Smith S, Tillisch K, Naliboff B, Mayer EA |title=Patients with chronic visceral pain show sex-related alterations in intrinsic oscillations of the resting brain |journal=J. Neurosci. |volume=33 |issue=29 |pages=11994–2002 |year=2013 |pmid=23864686 |pmc=3713732 |doi=10.1523/JNEUROSCI.5733-12.2013 |url=}}</ref>
* [[prefrontal cortex]] modulation may lead to increased perception of [[Viscus|visceral]] pain.
* Modulation of the mid-[[cingulate cortex]] is associated with alterations in the subjective sensations of pain.<ref name="pmid22108191">{{cite journal |vauthors=Larsson MB, Tillisch K, Craig AD, Engström M, Labus J, Naliboff B, Lundberg P, Ström M, Mayer EA, Walter SA |title=Brain responses to visceral stimuli reflect visceral sensitivity thresholds in patients with irritable bowel syndrome |journal=Gastroenterology |volume=142 |issue=3 |pages=463–472.e3 |year=2012 |pmid=22108191 |pmc=3288538 |doi=10.1053/j.gastro.2011.11.022 |url=}}</ref><ref name="pmid27144627">{{cite journal |vauthors=Mearin F, Lacy BE, Chang L, Chey WD, Lembo AJ, Simren M, Spiller R |title=Bowel Disorders |journal=Gastroenterology |volume= |issue= |pages= |year=2016 |pmid=27144627 |doi=10.1053/j.gastro.2016.02.031 |url=}}</ref>
* Patients with IBS have aberrant processing of central information, with decreased feedback on the emotional arousal network that controls the [[Autonomic nervous system|autonomic]] activity of the [[Gastrointestinal tract|gastrointestinal]] tract and changes gut [[motility]].<ref name="pmid23721972">{{cite journal |vauthors=Ellingson BM, Mayer E, Harris RJ, Ashe-McNally C, Naliboff BD, Labus JS, Tillisch K |title=Diffusion tensor imaging detects microstructural reorganization in the brain associated with chronic irritable bowel syndrome |journal=Pain |volume=154 |issue=9 |pages=1528–41 |year=2013 |pmid=23721972 |pmc=3758125 |doi=10.1016/j.pain.2013.04.010 |url=}}</ref><ref name="pmid20003075">{{cite journal |vauthors=Hall GB, Kamath MV, Collins S, Ganguli S, Spaziani R, Miranda KL, Bayati A, Bienenstock J |title=Heightened central affective response to visceral sensations of pain and discomfort in IBS |journal=Neurogastroenterol. Motil. |volume=22 |issue=3 |pages=276–e80 |year=2010 |pmid=20003075 |doi=10.1111/j.1365-2982.2009.01436.x |url=}}</ref>
* IBS is a [[brain]] [[Gastrointestinal tract|gut]] disorder as [[Rectum|rectal]] distension in patients causes increased engagement of regions of the [[brain]] associated with attentional and [[Behavior|behavioral]] responses.<ref name="pmid22108191">{{cite journal |vauthors=Larsson MB, Tillisch K, Craig AD, Engström M, Labus J, Naliboff B, Lundberg P, Ström M, Mayer EA, Walter SA |title=Brain responses to visceral stimuli reflect visceral sensitivity thresholds in patients with irritable bowel syndrome |journal=Gastroenterology |volume=142 |issue=3 |pages=463–472.e3 |year=2012 |pmid=22108191 |pmc=3288538 |doi=10.1053/j.gastro.2011.11.022 |url=}}</ref><ref name="pmid20600024">{{cite journal |vauthors=Elsenbruch S, Rosenberger C, Bingel U, Forsting M, Schedlowski M, Gizewski ER |title=Patients with irritable bowel syndrome have altered emotional modulation of neural responses to visceral stimuli |journal=Gastroenterology |volume=139 |issue=4 |pages=1310–9 |year=2010 |pmid=20600024 |doi=10.1053/j.gastro.2010.06.054 |url=}}</ref><ref name="pmid19651629">{{cite journal |vauthors=Elsenbruch S, Rosenberger C, Enck P, Forsting M, Schedlowski M, Gizewski ER |title=Affective disturbances modulate the neural processing of visceral pain stimuli in irritable bowel syndrome: an fMRI study |journal=Gut |volume=59 |issue=4 |pages=489–95 |year=2010 |pmid=19651629 |doi=10.1136/gut.2008.175000 |url=}}</ref>
* [[Stress (medicine)|Psychological stress]] also impacts the release of gut [[Inflammation|proinflammatory]] [[Cytokine|cytokines]], contributing to pain in [[Irritable bowel syndrome|IBS]] patients.<ref name="pmid19997094" />


* A study of blood samples from IBS patients found elevated levels of [[antibodies]] to the [[protozoan]] ''[[Blastocystis]]''.<ref name="HUSSAIN_1997">{{cite journal |author=Hussain R, Jaferi W, Zuberi S, ''et al'' |title=Significantly increased IgG2 subclass antibody levels to Blastocystis hominis in patients with irritable bowel syndrome |journal=Am. J. Trop. Med. Hyg. |volume=56|issue=3 |pages=301-6 |year=1997 |pmid=9129532 |doi=}}</ref>
==Genetic factors==
*IBS has high '''[[twin]] [[Concordance (genetics)|concordance]] and [[Family|familial]] [[aggregation]]''':<ref name="pmid11606493">{{cite journal |vauthors=Levy RL, Jones KR, Whitehead WE, Feld SI, Talley NJ, Corey LA |title=Irritable bowel syndrome in twins: heredity and social learning both contribute to etiology |journal=Gastroenterology |volume=121 |issue=4 |pages=799–804 |year=2001 |pmid=11606493 |doi= |url=}}</ref><ref name="pmid9707057">{{cite journal |vauthors=Morris-Yates A, Talley NJ, Boyce PM, Nandurkar S, Andrews G |title=Evidence of a genetic contribution to functional bowel disorder |journal=Am. J. Gastroenterol. |volume=93 |issue=8 |pages=1311–7 |year=1998 |pmid=9707057 |doi=10.1111/j.1572-0241.1998.440_j.x |url=}}</ref><ref name="pmid17509102">{{cite journal |vauthors=Lembo A, Zaman M, Jones M, Talley NJ |title=Influence of genetics on irritable bowel syndrome, gastro-oesophageal reflux and dyspepsia: a twin study |journal=Aliment. Pharmacol. Ther. |volume=25 |issue=11 |pages=1343–50 |year=2007 |pmid=17509102 |doi=10.1111/j.1365-2036.2007.03326.x |url=}}</ref><ref name="pmid16271334">{{cite journal |vauthors=Saito YA, Petersen GM, Locke GR, Talley NJ |title=The genetics of irritable bowel syndrome |journal=Clin. Gastroenterol. Hepatol. |volume=3 |issue=11 |pages=1057–65 |year=2005 |pmid=16271334 |doi= |url=}}</ref><ref name="pmid24041540">{{cite journal |vauthors=Wouters MM, Lambrechts D, Knapp M, Cleynen I, Whorwell P, Agréus L, Dlugosz A, Schmidt PT, Halfvarson J, Simrén M, Ohlsson B, Karling P, Van Wanrooy S, Mondelaers S, Vermeire S, Lindberg G, Spiller R, Dukes G, D'Amato M, Boeckxstaens G |title=Genetic variants in CDC42 and NXPH1 as susceptibility factors for constipation and diarrhoea predominant irritable bowel syndrome |journal=Gut |volume=63 |issue=7 |pages=1103–11 |year=2014 |pmid=24041540 |doi=10.1136/gutjnl-2013-304570 |url=}}</ref><ref name="pmid20234344">{{cite journal |vauthors=Saito YA, Petersen GM, Larson JJ, Atkinson EJ, Fridley BL, de Andrade M, Locke GR, Zimmerman JM, Almazar-Elder AE, Talley NJ |title=Familial aggregation of irritable bowel syndrome: a family case-control study |journal=Am. J. Gastroenterol. |volume=105 |issue=4 |pages=833–41 |year=2010 |pmid=20234344 |pmc=2875200 |doi=10.1038/ajg.2010.116 |url=}}</ref>
**IBS has higher [[Concordance (genetics)|concordance]] in [[Twin|monozygotic]] as compared to [[Twin|dizygotic]] twins.<ref name="pmid11606493" /><ref name="pmid9707057" /><ref name="pmid17509102" /><ref name="pmid17008364">{{cite journal |vauthors=Bengtson MB, Rønning T, Vatn MH, Harris JR |title=Irritable bowel syndrome in twins: genes and environment |journal=Gut |volume=55 |issue=12 |pages=1754–9 |year=2006 |pmid=17008364 |pmc=1856463 |doi=10.1136/gut.2006.097287 |url=}}</ref>
**Individuals with a biologic relative with [[Irritable bowel syndrome|IBS]] have two times a higher risk of developing [[Irritable bowel syndrome|IBS]]. <ref name="pmid10994826">{{cite journal |vauthors=Locke GR, Zinsmeister AR, Talley NJ, Fett SL, Melton LJ |title=Familial association in adults with functional gastrointestinal disorders |journal=Mayo Clin. Proc. |volume=75 |issue=9 |pages=907–12 |year=2000 |pmid=10994826 |doi=10.4065/75.9.907 |url=}}</ref>
*'''[[Single nucleotide polymorphism|Single nucleotide polymorphisms (SNPs)]] in genes:'''
**IBS has [[Single nucleotide polymorphism|SNPs]] in genes playing an important role in host-[[Microbiome|microbiota]] interaction ([[Toll-like receptor|TLR9]], [[Interleukin 6|IL-6]] and [[CDH11|CDH1]]), [[Immunity (medical)|immune]] activation and [[Epithelium|epithelial]] barriers. 
**[[Single nucleotide polymorphism|SNPs]] cause [[inflammation]] and increased [[permeability]] of the [[Gastrointestinal tract|GI tract]], leading to [[Abdominal pain|abdominal discomfort]] and increased [[motility]].<ref name="pmid20044998">{{cite journal |vauthors=Villani AC, Lemire M, Thabane M, Belisle A, Geneau G, Garg AX, Clark WF, Moayyedi P, Collins SM, Franchimont D, Marshall JK |title=Genetic risk factors for post-infectious irritable bowel syndrome following a waterborne outbreak of gastroenteritis |journal=Gastroenterology |volume=138 |issue=4 |pages=1502–13 |year=2010 |pmid=20044998 |doi=10.1053/j.gastro.2009.12.049 |url=}}</ref><ref name="pmid12477767">{{cite journal |vauthors=Gonsalkorale WM, Perrey C, Pravica V, Whorwell PJ, Hutchinson IV |title=Interleukin 10 genotypes in irritable bowel syndrome: evidence for an inflammatory component? |journal=Gut |volume=52 |issue=1 |pages=91–3 |year=2003 |pmid=12477767 |pmc=1773523 |doi= |url=}}</ref>
**Mutation of type V (alpha [[Protein subunit|subunit]]) of ''SCN5A''-encoded [[Voltage-gated ion channel|voltage gated]] [[sodium channel]] causes [[Irritable bowel syndrome|IBS]].<ref name="pmid16771953">{{cite journal |vauthors=Locke GR, Ackerman MJ, Zinsmeister AR, Thapa P, Farrugia G |title=Gastrointestinal symptoms in families of patients with an SCN5A-encoded cardiac channelopathy: evidence of an intestinal channelopathy |journal=Am. J. Gastroenterol. |volume=101 |issue=6 |pages=1299–304 |year=2006 |pmid=16771953 |doi=10.1111/j.1572-0241.2006.00507.x |url=}}</ref><ref name="pmid19056759">{{cite journal |vauthors=Saito YA, Strege PR, Tester DJ, Locke GR, Talley NJ, Bernard CE, Rae JL, Makielski JC, Ackerman MJ, Farrugia G |title=Sodium channel mutation in irritable bowel syndrome: evidence for an ion channelopathy |journal=Am. J. Physiol. Gastrointest. Liver Physiol. |volume=296 |issue=2 |pages=G211–8 |year=2009 |pmid=19056759 |pmc=2643921 |doi=10.1152/ajpgi.90571.2008 |url=}}</ref>
**[[Genome]] wide [[DNA methylation]] profiling is impaired in [[Irritable bowel syndrome|IBS]] and this involves genes linked to [[neuropeptide]] [[hormone]] function and [[Oxidative stress|oxidative]] stress.<ref name="pmid26670691">{{cite journal |vauthors=Mahurkar S, Polytarchou C, Iliopoulos D, Pothoulakis C, Mayer EA, Chang L |title=Genome-wide DNA methylation profiling of peripheral blood mononuclear cells in irritable bowel syndrome |journal=Neurogastroenterol. Motil. |volume=28 |issue=3 |pages=410–22 |year=2016 |pmid=26670691 |pmc=4760882 |doi=10.1111/nmo.12741 |url=}}</ref>
**IBS causes [[mutation]] in the [[neuropeptide]] S [[Receptor (biochemistry)|receptor]] [[gene]] (NPSR1) involved in [[Pain and nociception|nociception]], [[inflammation]] and [[anxiety]] with [[abdominal pain]].<ref name="pmid19732772">{{cite journal |vauthors=Camilleri M, Carlson P, Zinsmeister AR, McKinzie S, Busciglio I, Burton D, Zucchelli M, D'Amato M |title=Neuropeptide S receptor induces neuropeptide expression and associates with intermediate phenotypes of functional gastrointestinal disorders |journal=Gastroenterology |volume=138 |issue=1 |pages=98–107.e4 |year=2010 |pmid=19732772 |pmc=2813358 |doi=10.1053/j.gastro.2009.08.051 |url=}}</ref> 
**[[Gene|Genes]] involved in the regulation of [[Liver|hepatic]] [[bile acid]] [[Chemical synthesis|synthesis]] such as a functional ''Klothoβ'' [[gene]] are mutated in [[Irritable bowel syndrome|IBS]].<ref name="pmid22610000">{{cite journal |vauthors=Wong BS, Camilleri M, Carlson P, McKinzie S, Busciglio I, Bondar O, Dyer RB, Lamsam J, Zinsmeister AR |title=Increased bile acid biosynthesis is associated with irritable bowel syndrome with diarrhea |journal=Clin. Gastroenterol. Hepatol. |volume=10 |issue=9 |pages=1009–15.e3 |year=2012 |pmid=22610000 |pmc=3565429 |doi=10.1016/j.cgh.2012.05.006 |url=}}</ref><ref name="pmid21396369">{{cite journal |vauthors=Wong BS, Camilleri M, Carlson PJ, Guicciardi ME, Burton D, McKinzie S, Rao AS, Zinsmeister AR, Gores GJ |title=A Klothoβ variant mediates protein stability and associates with colon transit in irritable bowel syndrome with diarrhea |journal=Gastroenterology |volume=140 |issue=7 |pages=1934–42 |year=2011 |pmid=21396369 |pmc=3109206 |doi=10.1053/j.gastro.2011.02.063 |url=}}</ref>
*'''TNF polymorphisms:'''
**[[Single nucleotide polymorphism|SNPs]] in [[Tumour necrosis factor|tumour necrosis factor alpha]] ([[Tumor necrosis factor-alpha|TNFα)]] and genes coding for superfamily member 15 (''TNFSF15'') have proven associations with [[Irritable bowel syndrome|IBS]].<ref name="pmid12477767" /><ref name="pmid22684480">{{cite journal |vauthors=Swan C, Duroudier NP, Campbell E, Zaitoun A, Hastings M, Dukes GE, Cox J, Kelly FM, Wilde J, Lennon MG, Neal KR, Whorwell PJ, Hall IP, Spiller RC |title=Identifying and testing candidate genetic polymorphisms in the irritable bowel syndrome (IBS): association with TNFSF15 and TNFα |journal=Gut |volume=62 |issue=7 |pages=985–94 |year=2013 |pmid=22684480 |doi=10.1136/gutjnl-2011-301213 |url=}}</ref><ref name="pmid21636646">{{cite journal |vauthors=Zucchelli M, Camilleri M, Andreasson AN, Bresso F, Dlugosz A, Halfvarson J, Törkvist L, Schmidt PT, Karling P, Ohlsson B, Duerr RH, Simren M, Lindberg G, Agreus L, Carlson P, Zinsmeister AR, D'Amato M |title=Association of TNFSF15 polymorphism with irritable bowel syndrome |journal=Gut |volume=60 |issue=12 |pages=1671–1677 |year=2011 |pmid=21636646 |pmc=3922294 |doi=10.1136/gut.2011.241877 |url=}}</ref>
**[[Tumor necrosis factors|TNF]] [[polymorphisms]] are also associated with post [[Infection|infectious]] [[Irritable bowel syndrome|IBS]] such as ''rs4263839'' in ''TNFSF15'' and [[Irritable bowel syndrome|IBS]], particularly IBS associated with [[constipation]].<ref name="pmid22684480" /><ref name="pmid21636646" />


Specific forms of immune response that have been implicated in IBS symptoms include [[coeliac disease]] and other [[food allergy]] conditions.<ref name="Wangen_2006">Wangen, Dr. Stephen. ''The Irritable Bowel Syndrome Solution''. 2006. ISBN 0976853787. Excerpted with author's permission at [http://www.IBSTreatmentCenter.com/]</ref>  [[Coeliac disease]] (also spelled "celiac") is an immunoglobulin type A-(IgA) mediated allergic response to the [[gliadin]] protein in gluten grains,which exhibits wide variety of symptoms and can present as IBS.  "Some patients with diarrhea-predominant irritable bowel syndrome (IBS-D) may have undiagnosed celiac sprue (CS). Because the symptoms of CS respond to a gluten-free diet, testing for CS in IBS may prevent years of morbidity and attendant expense."<ref>{{cite journal |author=Spiegel BM, ''et al'' |title=Testing for celiac sprue in irritable bowel syndrome with predominant diarrhea: a cost-effectiveness analysis. |journal=Gastroenterology |volume=126 |issue=7 |pages=1721-32 |year=2004|pmid=15188167 |doi=}}</ref>  "Coeliac disease is a common finding among patients labelled as having irritable bowel syndrome. In this sub-group, a gluten free diet may lead to a significant improvement in symptoms. Routine testing for coeliac disease may be indicated in all patients being evaluated for irritable bowel syndrome."<ref>{{cite journal |author=Shahbazkhani B, ''et al''|title=Coeliac disease presenting with symptoms of irritable bowel syndrome. |journal=Aliment Pharmacol Therapy |volume=18 |issue=2|pages=231-5 |year=2003 |pmid=12869084 |doi=}}</ref> Food allergies, particularly those mediated by IgE and IgG-type antibodies have been implicated in IBS.<ref>{{cite journal |author=Li H, ''et al'' |title=Allergen-IgE complexes trigger CD23-dependent CCL20 release from human intestinal epithelial cells. |journal=Gastroenterology |volume=133 |issue=6 |pages=1905-15 |year=2007|pmid=18054562 |doi=}}</ref><ref>{{cite journal |Yang CM, Li YQ |title=The therapeutic effects of eliminating allergic foods according to food-specific IgG antibodies in irritable bowel syndrome - Article in Chinese |journal=Zhonghua Nei Ke Za Zhi.|volume=46 |issue=8 |pages=641-3 |year=2007 |pmid=17967233 |doi=}}</ref><ref>{{cite journal |author=Drisko ''et al'' |title=Treating Irritable Bowel Syndrome with a Food Elimination Diet Followed by Food Challenge and Probiotics |journal=Journal of the American College of Nutrition |volume=25 |issue=6 |pages=514-22 |year=2006 |pmid=17229899 |doi=}}</ref>
==Associated conditions==
Several medical [[comorbidities]] appear with greater frequency in [[Irritable bowel syndrome|IBS]] patients.   


===Active infections===
===Headache, Fibromyalgia, and Depression===
[[Irritable bowel syndrome|IBS]] patients may be identified with comorbidities such as [[headache]], [[fibromyalgia]] and [[depression]].<ref>{{cite journal |author=Cole JA, Rothman KJ, Cabral HJ, Zhang Y, Farraye FA |title=Migraine,[[fibromyalgia]], and depression among people with IBS:  a prevalence study |journal=BMC gastroenterology |volume=6 |issue=|pages=26 |year=2006 |pmid=17007634 |doi=10.1186/1471-230X-6-26}}</ref><ref name="pmid16614951">{{cite journal |author=Kurland JE, Coyle WJ, Winkler A, Zable E |title=Prevalence of irritable bowel syndrome and depression in [[fibromyalgia]] |journal=Dig. Dis. Sci. |volume=51 |issue=3 |pages=454-60 |year=2006|pmid=16614951 |doi=10.1007/s10620-006-3154-7}}</ref><ref name="pmid16042909">{{cite journal |author=Frissora CL, Koch KL|title=Symptom overlap and comorbidity of irritable bowel syndrome with other conditions |journal=Current gastroenterology reports|volume=7 |issue=4 |pages=264-71 |year=2005 |pmid=16042909 |doi=}}</ref>


<div class="noprint" style="clear: center; border: solid #aaa 1px; margin: 0 0 1em 1em;  background: #efeff9; width: 50%; padding: 4px; text-align: left; float: right;">
===Inflammatory Bowel Disease===
* [[Irritable bowel syndrome|IBS]] and [[Inflammatory bowel disease|IBD]] are interrelated diseases, as patients with [[Inflammatory bowel disease|IBD]] experience [[Irritable bowel syndrome|IBS]]-like symptoms when their [[Inflammatory bowel disease|IBD]] is in remission.<ref name="SIMREN_2002">{{cite journal |author=Simrén M, Axelsson J, Gillberg R, Abrahamsson H, Svedlund J, Björnsson ES|title=Quality of life in inflammatory bowel disease in remission: the impact of IBS-like symptoms and associated psychological factors |journal=Am. J. Gastroenterol. |volume=97 |issue=2 |pages=389-96 |year=2002 |pmid=11866278 |doi=}}</ref><ref name="MINDERHOUD_2004">{{cite journal |author=Minderhoud IM, Oldenburg B, Wismeijer JA, van Berge Henegouwen GP, Smout AJ|title=IBS-like symptoms in patients with inflammatory bowel disease in remission; relationships with quality of life and coping behavior |journal=Dig. Dis. Sci. |volume=49 |issue=3 |pages=469-74 |year=2004 |pmid=15139501 |doi=}}</ref><ref name="QUIGLEY_2005">{{cite journal |author=Quigley EM |title=Irritable bowel syndrome and inflammatory bowel disease: interrelated diseases? |journal=Chinese journal of digestive diseases |volume=6 |issue=3 |pages=122-32 |year=2005 |pmid=16045602|doi=10.1111/j.1443-9573.2005.00202.x}}</ref>
* [[Irritable bowel syndrome|IBS]] is believed to be a type of low-grade [[inflammatory bowel disease]] as serum markers associated with [[inflammation]] have also been found in patients with [[Irritable bowel syndrome|IBS]].<ref name="BERCIK_2005">{{cite journal |author=Bercik P, Verdu EF, Collins SM |title=Is irritable bowel syndrome a low-grade inflammatory bowel disease? |journal=Gastroenterol. Clin. North Am. |volume=34 |issue=2 |pages=235-45, vi-vii |year=2005|pmid=15862932 |doi=10.1016/j.gtc.2005.02.007}}</ref>
* [[Irritable bowel syndrome|IBS]] patients are16.3 times more likely to develop [[Inflammatory bowel disease|IBD]].<ref name="GARCIA_2000">{{cite journal |author=García Rodríguez LA, Ruigómez A, Wallander MA, Johansson S, Olbe L |title=Detection of colorectal tumor and inflammatory bowel disease during follow-up of patients with initial diagnosis of irritable bowel syndrome |journal=Scand. J. Gastroenterol. |volume=35 |issue=3 |pages=306-11 |year=2000 |pmid=10766326 |doi=}}</ref> 


{{"
===Abdominal Surgery===
|Clearly this study highlights a new concept in the potential pathogenesis of IBS.  An infectious cause may offer a tremendous opportunity to manage an otherwise frustrating disease -- both for patients and their treating physician.
* [[Irritable bowel syndrome|IBS]] patients are 87% more likely to undergo [[Abdomen|abdominal]] and [[Pelvis|pelvic]] [[surgery]], and three times more likely to undergo [[gallbladder]] [[surgery]].<ref name="pmid16416174">{{cite journal |author=Cole JA, Yeaw JM, Cutone JA, ''et al'' |title=The incidence of abdominal and pelvic surgery among patients with irritable bowel syndrome |journal=Dig. Dis. Sci. |volume=50 |issue=12 |pages=2268–75 |year=2005 |pmid=16416174|doi=10.1007/s10620-005-3047-1}}</ref>
|by Dr. David A. Johnson, President of the [[American College of Gastroenterology]] , commenting on results from study of Rifaximin in treatment of IBS<ref>{{cite journal |author=Johnson, David. |title=Viewpoints: Efficacy of Rifaximin vs Placebo in Reducing Symptoms in Adults With IBS. |journal=Medscape Gastroenterology |volume=8 |issue=2 |year=2006|url=http://www.medscape.com/viewarticle/547055}}</ref>
* [[Irritable bowel syndrome|IBS]] patients were twice as likely to undergo [[hysterectomy]].<ref name="pmid15188159">{{cite journal |author=Longstreth GF, Yao JF|title=Irritable bowel syndrome and surgery: a multivariable analysis |journal=Gastroenterology |volume=126 |issue=7 |pages=1665–73|year=2004 |pmid=15188159 |doi=}}</ref>
}}


</div>
===Endometriosis===
There is a statistically significant link between [[Migraine|migraine headaches]], [[Irritable bowel syndrome|IBS]], and [[endometriosis]].<ref name="pmid17635599">{{cite journal |author=Tietjen GE, Bushnell CD, Herial NA, Utley C, White L, Hafeez F|title=Endometriosis is associated with prevalence of comorbid conditions in migraine |journal=Headache |volume=47 |issue=7|pages=1069-78 |year=2007 |pmid=17635599 |doi=10.1111/j.1526-4610.2007.00784.x}}</ref>


There is research to support IBS being caused by an as-yet undiscovered active infection.  Most recently, a study has found that the antibiotic [[Rifaximin]] provides sustained relief for IBS patients.<ref name="pmid17043337">{{cite journal |author=Pimentel M, Park S, Mirocha J, Kane SV, Kong Y |title=The effect of a nonabsorbed oral antibiotic (rifaximin) on the symptoms of the irritable bowel syndrome: a randomized trial |journal=Ann. Intern. Med. |volume=145 |issue=8 |pages=557-63 |year=2006 |pmid=17043337 |doi=}}</ref> While some researchers see this as evidence that IBS is related to an undiscovered agent, others believe IBS patients suffer from overgrowth of [[Gut flora|intestinal flora]] and the antibiotics are effective in reducing the overgrowth (known as ''[[Small bowel bacterial overgrowth syndrome|small intestinal bacterial overgrowth]]'').<ref name="pmid17148502">{{cite journal |author=Posserud I, Stotzer PO, Björnsson ES, Abrahamsson H, Simrén M |title=Small intestinal bacterial overgrowth in patients with irritable bowel syndrome |journal=Gut |volume=56 |issue=6 |pages=802-8 |year=2007 |pmid=17148502 |doi=10.1136/gut.2006.108712}}</ref> Other researchers have focused on an unrecognized [[protozoa]]l infection as a cause of IBS<ref name="STARK_2007">{{cite journal|author=Stark D, van Hal S, Marriott D, Ellis J, Harkness J |title=Irritable bowel syndrome: a review on the role of intestinal protozoa and the importance of their detection and diagnosis |journal=Int. J. Parasitol. |volume=37 |issue=1 |pages=11-20 |year=2007|pmid=17070814 |doi=10.1016/j.ijpara.2006.09.009}}</ref> as certain protozoal infections occur more frequently in IBS patients.<ref name="YAKOOB_2004">{{cite journal |author=Yakoob J, Jafri W, Jafri N, ''et al'' |title=Irritable bowel syndrome: in search of an etiology: role of Blastocystis hominis |journal=Am. J. Trop. Med. Hyg. |volume=70 |issue=4 |pages=383-5 |year=2004 |pmid=15100450|doi=}}</ref><ref name="GIACOM_1999">{{cite journal |author=Giacometti A, Cirioni O, Fiorentini A, Fortuna M, Scalise G|title=Irritable bowel syndrome in patients with Blastocystis hominis infection |journal=Eur. J. Clin. Microbiol. Infect. Dis.|volume=18 |issue=6 |pages=436-9 |year=1999 |pmid=10442423 |doi=}}</ref>  Two of the protozoa investigated have a high prevalence in industrialized countries and infect the bowel, but little is known about them as they are recently emerged pathogens.
==Medical conditions that accompany IBS==
Several medical [[comorbidities]] appear with greater frequency in [[Irritable bowel syndrome|IBS]] patients.   


===Headache, Fibromyalgia, and Depression===
[[Irritable bowel syndrome|IBS]] patients may be identified with comorbidities such as [[headache]], [[fibromyalgia]] and [[depression]].<ref name="pmid16614951">{{cite journal |author=Kurland JE, Coyle WJ, Winkler A, Zable E |title=Prevalence of irritable bowel syndrome and depression in [[fibromyalgia]] |journal=Dig. Dis. Sci. |volume=51 |issue=3 |pages=454-60 |year=2006|pmid=16614951 |doi=10.1007/s10620-006-3154-7}}</ref><ref name="pmid16042909">{{cite journal |author=Frissora CL, Koch KL|title=Symptom overlap and comorbidity of irritable bowel syndrome with other conditions |journal=Current gastroenterology reports|volume=7 |issue=4 |pages=264-71 |year=2005 |pmid=16042909 |doi=}}</ref><ref>{{cite journal |author=Cole JA, Rothman KJ, Cabral HJ, Zhang Y, Farraye FA |title=Migraine,[[fibromyalgia]], and depression among people with IBS:  a prevalence study |journal=BMC gastroenterology |volume=6 |issue=|pages=26 |year=2006 |pmid=17007634 |doi=10.1186/1471-230X-6-26}}</ref>


''[[Blastocystis]]'' is a single-celled organism which has been reported to produce symptoms of abdominal pain, constipation and diarrhea in patients, along with headaches and depression,<ref name="QADRI_1989">{{cite journal |author=Qadri SM, al-Okaili GA, al-Dayel F |title=Clinical significance of Blastocystis hominis |journal=J. Clin. Microbiol. |volume=27 |issue=11 |pages=2407-9|year=1989 |pmid=2808664 |doi=}}</ref> though these reports are contested by some physicians.<ref name="MARKELL_1986">{{cite journal|author=Markell EK, Udkow MP |title=Blastocystis hominis: pathogen or fellow traveler? |journal=Am. J. Trop. Med. Hyg. |volume=35|issue=5 |pages=1023-6 |year=1986 |pmid=3766850 |doi=}}</ref>  Studies from research hospitals in various countries have identified high [[Blastocystis]] infection rates in IBS patients, with 38% being reported from [[London School of Hygiene & Tropical Medicine]],<ref name="WINDSOR_2007">{{cite journal |author=Windsor J |title=B. hominis and D. fragilis: Neglected human protozoa|journal=British Biomedical Scientist |pages=524-7 |year=2007 |pmid= |doi= |url=http://www.ibms.org/index.cfm?method=publications.biomedical_scientist&subpage=contents_2007_July}}</ref> 47% reported from the Department of Gastroenterology at [[Aga Khan University]] in Pakistan<ref name="YAKOOB_2004" /> and 18.1% reported from the Institute of Diseases and Public Health at [[University of Ancona]] in Italy.<ref name="GIACOM_1999" />  Reports from all three groups indicate a [[Blastocystis]] prevalence of approximately 7% in non-IBS patients. Researchers have noted that clinical diagnostics fail to identify infection,<ref name="STENSVOLD_2006">{{cite journal |author=Stensvold R, Brillowska-Dabrowska A, Nielsen HV, Arendrup MC |title=Detection of Blastocystis hominis in unpreserved stool specimens by using polymerase chain reaction |journal=J. Parasitol. |volume=92 |issue=5|pages=1081-7 |year=2006 |pmid=17152954 |doi=}}</ref> and ''Blastocystis'' may not respond to treatment with common antiprotozoals.<ref name="pmid15250669">{{cite journal |author=Yakoob J, Jafri W, Jafri N, Islam M, Asim Beg M |title=In vitro susceptibility of Blastocystis hominis isolated from patients with irritable bowel syndrome |journal=Br. J. Biomed. Sci. |volume=61|issue=2 |pages=75-7 |year=2004 |pmid=15250669 |doi=}}</ref><ref name="pmid10357863">{{cite journal |author=Haresh K, Suresh K, Khairul Anus A, Saminathan S |title=Isolate resistance of Blastocystis hominis to metronidazole |journal=Trop. Med. Int. Health|volume=4 |issue=4 |pages=274-7 |year=1999 |pmid=10357863 |doi=}}</ref><ref name="pmid3766850">{{cite journal |author=Markell EK, Udkow MP |title=Blastocystis hominis: pathogen or fellow traveler? |journal=Am. J. Trop. Med. Hyg. |volume=35 |issue=5 |pages=1023-6|year=1986 |pmid=3766850 |doi=}}</ref><ref name="pmid10566723">{{cite journal |author=Ok UZ, Girginkardeşler N, Balcioğlu C, Ertan P, Pirildar T, Kilimcioğlu AA |title=Effect of trimethoprim-sulfamethaxazole in Blastocystis hominis infection |journal=Am. J. Gastroenterol. |volume=94 |issue=11 |pages=3245-7 |year=1999 |pmid=10566723 |doi=}}</ref>   
===Inflammatory Bowel Disease===
* [[Irritable bowel syndrome|IBS]] and [[Inflammatory bowel disease|IBD]] are interrelated diseases, as patients with [[Inflammatory bowel disease|IBD]] experience [[Irritable bowel syndrome|IBS]]-like symptoms when their [[Inflammatory bowel disease|IBD]] is in remission.<ref name="SIMREN_2002">{{cite journal |author=Simrén M, Axelsson J, Gillberg R, Abrahamsson H, Svedlund J, Björnsson ES|title=Quality of life in inflammatory bowel disease in remission: the impact of IBS-like symptoms and associated psychological factors |journal=Am. J. Gastroenterol. |volume=97 |issue=2 |pages=389-96 |year=2002 |pmid=11866278 |doi=}}</ref><ref name="MINDERHOUD_2004">{{cite journal |author=Minderhoud IM, Oldenburg B, Wismeijer JA, van Berge Henegouwen GP, Smout AJ|title=IBS-like symptoms in patients with inflammatory bowel disease in remission; relationships with quality of life and coping behavior |journal=Dig. Dis. Sci. |volume=49 |issue=3 |pages=469-74 |year=2004 |pmid=15139501 |doi=}}</ref><ref name="QUIGLEY_2005">{{cite journal |author=Quigley EM |title=Irritable bowel syndrome and inflammatory bowel disease: interrelated diseases? |journal=Chinese journal of digestive diseases |volume=6 |issue=3 |pages=122-32 |year=2005 |pmid=16045602|doi=10.1111/j.1443-9573.2005.00202.x}}</ref>
* [[Irritable bowel syndrome|IBS]] is believed to be a type of low-grade [[inflammatory bowel disease]] as serum markers associated with [[inflammation]] have also been found in patients with [[Irritable bowel syndrome|IBS]] .<ref name="BERCIK_2005">{{cite journal |author=Bercik P, Verdu EF, Collins SM |title=Is irritable bowel syndrome a low-grade inflammatory bowel disease? |journal=Gastroenterol. Clin. North Am. |volume=34 |issue=2 |pages=235-45, vi-vii |year=2005|pmid=15862932 |doi=10.1016/j.gtc.2005.02.007}}</ref>  
* [[Irritable bowel syndrome|IBS]] patients are16.3 times more likely to develop [[Inflammatory bowel disease|IBD]].<ref name="GARCIA_2000">{{cite journal |author=García Rodríguez LA, Ruigómez A, Wallander MA, Johansson S, Olbe L |title=Detection of colorectal tumor and inflammatory bowel disease during follow-up of patients with initial diagnosis of irritable bowel syndrome |journal=Scand. J. Gastroenterol. |volume=35 |issue=3 |pages=306-11 |year=2000 |pmid=10766326 |doi=}}</ref>   


[[Image:Wiki ibs cause figures.jpg|thumb|800px|center|Prevalence of protozoal infections in industrialized countries (United States and Canada) in 21st century.<ref name="CMAJ_2006" /><ref name="pmid12224595">{{cite journal |author=Amin OM |title=Seasonal prevalence of intestinal parasites in the United States during 2000 |journal=Am. J. Trop. Med. Hyg. |volume=66 |issue=6|pages=799-803 |year=2002 |pmid=12224595 |doi=}}</ref>]]
===Abdominal Surgery===
* [[Irritable bowel syndrome|IBS]] patients are 87% more likely to undergo [[Abdomen|abdominal]] and [[Pelvis|pelvic]] [[surgery]], and three times more likely to undergo [[gallbladder]] [[surgery]].<ref name="pmid16416174">{{cite journal |author=Cole JA, Yeaw JM, Cutone JA, ''et al'' |title=The incidence of abdominal and pelvic surgery among patients with irritable bowel syndrome |journal=Dig. Dis. Sci. |volume=50 |issue=12 |pages=2268–75 |year=2005 |pmid=16416174|doi=10.1007/s10620-005-3047-1}}</ref>
* [[Irritable bowel syndrome|IBS]] patients were twice as likely to undergo [[hysterectomy]].<ref name="pmid15188159">{{cite journal |author=Longstreth GF, Yao JF|title=Irritable bowel syndrome and surgery: a multivariable analysis |journal=Gastroenterology |volume=126 |issue=7 |pages=1665–73|year=2004 |pmid=15188159 |doi=}}</ref>


''[[Dientamoeba fragilis]]'' is a single-celled organism which produces abdominal pain and diarrhea.  Studies have reported a high incidence of infection in developed countries, and symptoms of patients resolve following antibiotic treatment.<ref name="CMAJ_2006">{{cite journal |author=Lagacé-Wiens PR, VanCaeseele PG, Koschik C |title=Dientamoeba fragilis: an emerging role in intestinal disease |journal=CMAJ : Canadian Medical Association journal &#61; journal de l'Association medicale canadienne|volume=175 |issue=5 |pages=468-9 |year=2006 |pmid=16940260 |doi=10.1503/cmaj.060265}}</ref><ref name="STENSVOLD_2007f">{{cite journal |author=Stensvold CR, Arendrup MC, Mølbak K, Nielsen HV |title=The prevalence of Dientamoeba fragilis in patients with suspected enteroparasitic disease in a metropolitan area in Denmark |journal=Clin. Microbiol. Infect. |volume=13 |issue=8|pages=839-42 |year=2007 |pmid=17610603 |doi=10.1111/j.1469-0691.2007.01760.x}}</ref> One study reported on a large group of patients with IBS-like symptoms who were found to be infected with ''Dientamoeba fragilis'' and experienced resolution of symptoms following treatment.<ref name="BORODY_2002">{{cite journal |author=Borody T, Warren E, Wettstein A, et al. | title = Eradication of Dientamoeba fragilis can resolve IBS-like symptoms.  | journal=J Gastroenterol Hepatol | year= 2002 | volume=17 | issue=Suppl; pages=A103}}</ref> Researchers have noted that methods used clinically may fail to detect some ''[[Dientamoeba fragilis]]'' infections.<ref name="STENSVOLD_2007f" />
===Endometriosis===
There is a statistically significant link between [[Migraine|migraine headaches]], [[Irritable bowel syndrome|IBS]], and [[endometriosis]].<ref name="pmid17635599">{{cite journal |author=Tietjen GE, Bushnell CD, Herial NA, Utley C, White L, Hafeez F|title=Endometriosis is associated with prevalence of comorbid conditions in migraine |journal=Headache |volume=47 |issue=7|pages=1069-78 |year=2007 |pmid=17635599 |doi=10.1111/j.1526-4610.2007.00784.x}}</ref>
 
==Gross Pathology==
*On [[Gross examination|gross]] [[pathology]], the [[Gastrointestinal tract|GI tract]] appears normal in [[Irritable bowel syndrome|IBS]].
 
==Microscopic Pathology==
[[Microscopic]] changes that may be found in [[Irritable bowel syndrome|IBS]] patients are as follows:<ref name="pmid12454854" /><ref name="pmid14988823" /><ref name="pmid14724817">{{cite journal |vauthors=Dunlop SP, Jenkins D, Neal KR, Spiller RC |title=Relative importance of enterochromaffin cell hyperplasia, anxiety, and depression in postinfectious IBS |journal=Gastroenterology |volume=125 |issue=6 |pages=1651–9 |year=2003 |pmid=14724817 |doi= |url=}}</ref><ref name="pmid11076879">{{cite journal |vauthors=Spiller RC, Jenkins D, Thornley JP, Hebden JM, Wright T, Skinner M, Neal KR |title=Increased rectal mucosal enteroendocrine cells, T lymphocytes, and increased gut permeability following acute Campylobacter enteritis and in post-dysenteric irritable bowel syndrome |journal=Gut |volume=47 |issue=6 |pages=804–11 |year=2000 |pmid=11076879 |pmc=1728147 |doi= |url=}}</ref><ref name="pmid10026328">{{cite journal |vauthors=Gwee KA, Leong YL, Graham C, McKendrick MW, Collins SM, Walters SJ, Underwood JE, Read NW |title=The role of psychological and biological factors in postinfective gut dysfunction |journal=Gut |volume=44 |issue=3 |pages=400–6 |year=1999 |pmid=10026328 |pmc=1727402 |doi= |url=}}</ref><ref name="pmid12873581">{{cite journal |vauthors=Dunlop SP, Jenkins D, Spiller RC |title=Distinctive clinical, psychological, and histological features of postinfective irritable bowel syndrome |journal=Am. J. Gastroenterol. |volume=98 |issue=7 |pages=1578–83 |year=2003 |pmid=12873581 |doi=10.1111/j.1572-0241.2003.07542.x |url=}}</ref><ref name="pmid8359068">{{cite journal |vauthors=Weston AP, Biddle WL, Bhatia PS, Miner PB |title=Terminal ileal mucosal mast cells in irritable bowel syndrome |journal=Dig. Dis. Sci. |volume=38 |issue=9 |pages=1590–5 |year=1993 |pmid=8359068 |doi= |url=}}</ref><ref name="pmid11012945">{{cite journal |vauthors=O'Sullivan M, Clayton N, Breslin NP, Harman I, Bountra C, McLaren A, O'Morain CA |title=Increased mast cells in the irritable bowel syndrome |journal=Neurogastroenterol. Motil. |volume=12 |issue=5 |pages=449–57 |year=2000 |pmid=11012945 |doi= |url=}}</ref><ref name="pmid12692417">{{cite journal |vauthors=Park CH, Joo YE, Choi SK, Rew JS, Kim SJ, Lee MC |title=Activated mast cells infiltrate in close proximity to enteric nerves in diarrhea-predominant irritable bowel syndrome |journal=J. Korean Med. Sci. |volume=18 |issue=2 |pages=204–10 |year=2003 |pmid=12692417 |pmc=3055014 |doi=10.3346/jkms.2003.18.2.204 |url=}}</ref><ref name="pmid15247174">{{cite journal |vauthors=Wang LH, Fang XC, Pan GZ |title=Bacillary dysentery as a causative factor of irritable bowel syndrome and its pathogenesis |journal=Gut |volume=53 |issue=8 |pages=1096–101 |year=2004 |pmid=15247174 |pmc=1774156 |doi=10.1136/gut.2003.021154 |url=}}</ref><ref name="pmid2733385">{{cite journal |vauthors=Salzmann JL, Peltier-Koch F, Bloch F, Petite JP, Camilleri JP |title=Morphometric study of colonic biopsies: a new method of estimating inflammatory diseases |journal=Lab. Invest. |volume=60 |issue=6 |pages=847–51 |year=1989 |pmid=2733385 |doi= |url=}}</ref><ref name="pmid13907162">{{cite journal |vauthors=HIATT RB, KATZ L |title=Mast cells in inflammatory conditions of the gastrointestinal tract |journal=Am. J. Gastroenterol. |volume=37 |issue= |pages=541–5 |year=1962 |pmid=13907162 |doi= |url=}}</ref>
 
{| class="wikitable"
! align="center" style="background: #4479BA; color: #FFFFFF; " |LOCATION
! align="center" style="background: #4479BA; color: #FFFFFF; " ! |LAYER OF INTESTINE INVOLVED
! align="center" style="background: #4479BA; color: #FFFFFF; " ! |MAST CELLS
! align="center" style="background: #4479BA; color: #FFFFFF; " ! |T LYMPHOCYTES
! align="center" style="background: #4479BA; color: #FFFFFF; " ! |ENTEROCHROMAFFIN CELLS
|-
|[[Rectum]]
|[[Mucous membrane|Mucosa]]
| +++/-
| +/-
| +/-
|-
|[[Terminal ileum]]
|[[Mucous membrane|Mucosa]]
| -
| ++
| -
|-
|[[Cecum]]
|[[Mucous membrane|Mucosa]]
| ++
| -
| -
|-
|[[Colon (anatomy)|Colon]]
|[[Muscularis externa]]
| +/-
| -
| -
|-
|[[Jejunum]]
|[[Myentric]] [[plexus]]
| ++
| -
| -
|}


==References==
==References==
{{Reflist|2}}
{{Reflist|2}}
[[Category:Gastroenterology]]
[[Category:Primary care]]
[[Category:Needs overview]]


{{WH}}
{{WH}}
{{WS}}
{{WS}}
[[Category: (name of the system)]]

Latest revision as of 19:15, 28 August 2021

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Editor-In-Chief: C. Michael Gibson, M.S., M.D. [1]; Associate Editor(s)-in-Chief: Sudarshana Datta, MD [2]

Overview

Irritable Bowel Syndrome is caused by a complex interaction of various factors such as intrinsic gastrointestinal factors, CNS dysregulation and psychosocial factors, genetic, and environmental factors. Intrinsic gastrointestinal factors include motor abnormalities, visceral hypersensitivity, immune activation, mucosal inflammation, altered gut microbiota, and abnormal serotonin pathways. Visceral hypersensitivity refers to a decreased threshold for the perception of visceral stimuli that affects spinal excitability, brain stem and cortical modulation, activation of specific gastrointestinal mediators, and recruitment of peripheral silent nociceptors. Immune activation and mucosal inflammation involves an interaction of lymphocytes, mast cells, and proinflammatory cytokines. Environmental factors encompass dietary changes and infections. Psychosocial factors such as stress, anxiety, and depression directly shape adult connectivity in the executive control network consisting of structures such as the insula, anterior cingulate cortex, and the thalamus. Semipermanent or permanent changes in complex neural circuits lead to central pain amplification contributing to abdominal pain in IBS patients. The dorsolateral prefrontal cortex activity (responsible for vigilance and alertness of the human brain) and the mid-cingulate cortex (engaged in attention pathways and responses) is reduced in IBS patients. This reduction may lead to alterations in the subjective sensations of pain. Genetic factors also play a role in IBS. IBS has a high twin concordance and familial aggregation. IBS is associated with single nucleotide polymorphisms (SNPs) in genes involved in immune activation, neuropeptide hormone function, oxidative stress, nociception, permeability of the GI tract, host-microbiota interaction, inflammation, and TNF activity.

Pathophysiology

Pathogenesis

IBS occurs as a result of an interplay between four main factors:


 
 
 
 
 
CNS dysregulation and psychosocial factors
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
Intrinsic gastrointestinal factors:
• Motor abnormalities
• Visceral hypersensitivity
• Immune activation and mucosal inflammation
• Altered gut microbiota
• Abnormal serotonin pathways
 
 
IRRITABLE BOWEL SYNDROME
 
 
 
Genetic factors:
• Twin concordance
• Familial aggregation
• Single nucleotide polymorphisms(SNPs)
• TNF polymorphism
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
Environmental factors:
•Diet
•Infections
 
 
 

Environmental factors

Intrinsic gastrointestinal factors


 
 
 
 
 
 
 
 
 
 
 
 
Spinal hyperexcitability
 
Activation of
• N-methyl D aspartate (NMDA) receptor
• nitric oxide
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
Central (brainstem and cortical) modulation
 
Increased activation of:
• Anterior cingulate cortex
• Thalamus
• insula
 
 
 
 
 
 
 
 
 
 
 
Visceral hypersensitivity
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
Activation of specific gastrointestinal mediators
 
Kinins and serotonin activation lead to afferent nerve fiber sensitization
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
Recruitment of peripheral silent nociceptors
 
Increased end organ sensitivity due to hormonal or immune activation
 
 
 
 
 
 




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