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Irritable Bowel Syndrome

Irritable bowel syndrome ( IBS ) is a functional disorder in which abdominal pain or discomfort is associated with defecation and/or a change in bowel habit. Sensations of discomfort ( bloating ) , distension, and disordered defecation are commonly associated features. In some languages, the words ” bloating ” and distension ” may be represented by the same term ( WHO Global Guidelines IBS a Global Perspective 2015 )

Current diagnostic criteria of IBS is based on Rome IV 
( Rome III was updated in 2016 ) Most important change is the elimination of the word ” discomfort ” – considered too vague

Rome IV IBS Diagnostic Criteria

Abdominal pain atleast 1 day per week during the last 3 months that is 
associated with atleast 2 of the following & symptom onset atleast 6 months before the diagnosis
 related to defecation associated with a change in frequency of stool associated with a change in the form ( appearance ) of stool.

For a precise sub-classification the patient should not be taking any medication to treat their symptom , including laxatives or anti-diarrhoeal medication during the period of evaluation.

How common – IBS is the most prevalent of the functional GI disorders ( FGIDs ) Global prevalence 1 to 20 % worldwide ( 10-15 % in N America & Europe ) Women diagnosed 2-3 times ↑ often as men Aggregates within family More in age range 30-49 yrs although can present in any age Asians and Hispanics -less prevalent compared to other ethnic groups Health related QoL is similar to those with asthma & worse than those with chronic liver disease Also prevalent in paediatric population and estimated prevalence is similar to adults.

What happens – No known structural ,anatomical or physiological abnormality that 
accounts for the symptoms ,Role of various abnormalities 
proposed as abnormal gastrointestinal motility intestinal inflammation and the microbiome infection visceral hypersensitivity alteration in gut secretory and motor function brain-gut axis disturbance

IBS is a relapsing functional bowel disorder defined by 
symptoms-based diagnostic criteria in the absence of detectable organic causes

The ” biopsyhcosocial ” model proposes that IBS is a multifactorial disorder , deriving from a potential multitude of etiopathogenic factors as environmental , psychologic and physiologic
 Infectious gastroenteritis is often a trigger for IBS in 3rd of patients but only 7-30 % of patients with acute GE develop IBS Aberrant brain neurocircuitary ( anterior cingulate , insula ) Food- patients often perceive food to be an important trigger Genetic basis -substantial evidence exists to indicate a genetic basis of IBS but no single genetic defect reliable accounts for all the cases.

Disease burden-negatively affects QoL and work productivity significant cost – direct medical costs attributed to IBS in the US , excluding prescriptions and OTC were estimated at 1.5 -10 billion $s in 2005 patients with IBS have been known to undergo more diagnostic tests ,imaging and surgical procedures compared to people without IBS its is also thought that because IBS is not life threatening and does not reduce life-expectancy it remains underestimated.

Chronic in duration Type of pain – intermittent or continuous Previous pain episodes Where is the pain located – it may be well localised for e.g left lower quadrant in a few or may move around Often acute episodes of sharp pain are superimposed on a more constant dull ache Pain often related to meals and patients often perceive food to be an important trigger Relief with defecation or passing of flatus but may not fully relieve it Nocturnal pain is not common in IBS and is a red flag sign

Abdominal symptoms
 bloating distension borborgymi flatulence

Other symptoms ( extra-intestinal ) which support a diagnosis of IBS include migraine headaches , interstitial cystitis , dyspareunia and constant lethargy

IBS Subtypes –Following an evaluation – we can determine the predominant bowel habit to ascertain the IBS subtype based on stool pattern ( tool as The Bristol Stool Form Scale can be used here )
 IBS C- with constipation IBS -D diarrhoea predominant IBS-M mixed diarrhoea and constipation IBS-U unclassified symptoms cannot be categorized into one of the above subtypes

Patients often switch between subtypes -aim of this practice is to homogeneity of patients recruited for clinical trials , guide effective diagnosis and therapy and improve knowledge of potential pathophysiological mechanisms.

Tests –FBC ESR CRP Coeliac screen ( recommended ) Faecal calprotectin testing- elevated calprotectin indicates bowel inflammation Consider Ca 125 and +/- US for women aged > 50 yrs presenting with symptoms suggestive of IBS TFT – not included in NICE guidance but can be checked if clinical suspicion of thyroid illness is high ( is part of routine chemical profile ordered by most clinicians )

Tests not required -Endoscopy , Radiology , Hydrogen breath tests , Stool MC&S , FOB 

Current understanding advocates minimized laboratory and invasive testing ( cost , reinforce illness behaviour )

Yield of investigations requested to r/o an organic pathology in patients presenting with IBS symptoms is low.

Age > 50 yrs Persistent diarrhoea Fever Acute symptoms Progressive symptoms Waking at night due to GI symptoms e.g nocturnal pain or passage of stools Anorexia or unexplained wt loss Rectal bleeding ( melana or hematochezia ) Abdominal or rectal mass Anaemia Ascites Family history of colon cancer or inflammatory bowel disease Painless diarrhoea Recent use of antibiotics Newly onset progressive symptoms Onset of symptoms after 50 yrs Gluten intolerance ( 4 % overlap with coelaic disease )

IBS management difficulties-The spectrum , duration and severity of symptoms can vary significantly among individuals Symptoms of IBS can mimic those associated with organic illnesses – this presents a significant diagnostic challenge Although Rome IV criteria has been proposed for diagnosis – most primary care clinicians ( where IBS is usually diagnosed ) do not use the Rome criteria for making the diagnosis No specific biomarker available which can confirm or r/o an IBS diagnosis Dietary intolerance’s particularly lactose are present in 1/3rd of patients with IBS Therapy options – several are available but many have not been evaluated in high-quality RCTs , gaps in knowledge about IBS remains and limitations in the available data No universally agreed primary end point for IBS has been developed with good measurement science ie studies use different end points are used in clinical trials .

Diagnosis – a simplified approach to irritable bowel syndrome-Patient presents with recurrent bothersome symptoms or abdominal pain AND altered bowel habits 
( constipation , diarrhoea or both ) for atleast 3 months-Assess- History and physical examination 
Minimal investigations

 If organic cause suspected consider further investigations/ referral-No concerns for 
organic pathology – Establish positive IBS diagnosis.

Strategy –Understand what bothers the patient most- ie predominant symptoms-How does IBS affect the patient ? ie impact on ADLs , QoL-Advice reassurance , education and sharing information-Address any psychological co-morbidities that could contribute to the presence of IBS or making it worse-Individualized approach-advice lifestyle modifications for e.g Exercise , diet and dietary manipulation as first line for all types of IBS-If no response to conservative management , consider pharmacological & other therapies take into account
 pre-dominant symptom quality of evidence individual patient assessment patient preference and availability

Pharmacological measures –
Laxatives -Dietary fiber ,osmotic laxatives ( lactulose has not been studied effective but may worse bloating ) preferred over stimulant laxatives

Lubiprostone-chloride channel type 2 activator -triggers intestinal chloride secretion followed by obligatory Na and fluid transit into the lumen. Lubiprostone has been shown to provide significant relief in symptoms including bloating , bowel movement frequency , abdominal pain , straining , constipation severity and stool consistency.

Linaclotide -novel guanylate-cyclase agonist that upregulates secretion of chloride followed by Na and fluid into the bowel lumen- approved for IBS-D- works by increasing fluid secretion and accelerating intestinal transit and to taget abdominal pain by reducing visceral hypersensitivity

Anti-spasmodics-Have weak recommendations and quality of evidence is low- the following could be considered otilonium , pinavrium , hyoscine , cimetropium , drotaverine and dicylomine
Anti-depressants TCIs ( best studied nortriptyline , amitriptyline ) are recommended by ACG for overall symptom improvement ( strong recommendation and high quality of evidence ) 
SSRIs-for overall improvement in IBS patients ( weak recommendation , QoE low ) Consider citalopram – has effect on colonic tone and sensitivity , paroxetine has anti-cholinergic effects useful in diarrhoea
Venlafaxine is an alternative-greater pain suppression than SSRI-it also has peripheral effects inducing colonic relaxation in health volunteers.

Loperamide –Only agent with RCT data supporting use , its a Mu receptor agonist which improves diarrhoea by decreasing peristalsis , prolonging GI transit time and via reduction of fluid secretion in the intestinal lumen.

Peppermint-reported efficacy is effective and quality of evidence is moderate use supported by ACG

Others –Several other agents have been tried to help patients with IBS. Agents which are not first line or not commonly used in UK primary care include ondansetron , eluxdoline , rifaximin, cholestyramine .

Psychological therapies –Therapies like CBT , psyhcodynamic therapy have shown to be beneficial but the quality of evidence is low. They are also not available widely available

FODMAP Diet-FODMAP is an exclusion diet which could be tried after conservative dietary management strategies have failed. It may take up to 8 weeks for symptom response. Long term consequences not known and quality of evidence is very low

Probiotics –May be effective , the quality of evidence is low ACG recommends use as a group to improve global symptoms as well as bloating and flatulence.

Gluten free diet-ACG suggests against a gluten-free or exclusion diet based upon antibody or leukocytes activation test for overall symptoms improvement

Arrange a F/U for e.g in 4-6 weeks if a therapy is being trialed & consider a referral if no response to ongoing treatment

 references 

  1. World Gastroenterology Organisation Global Guidelines Irritable Syndrome : a Global
 Perspective Update September 2015 via https://www.spg.pt/wp-content/
uploads/2015/11/2015-IBS.pdf

  2. Irritable Bowel Syndrome: Modern Concepts and Management Options Gregory S Sayuk MD et al American Journal of Gastroenterology https://www.amjmed.com/article/S0002-9343(15)00168-0/pdf 
  3. Irritable Bowel Syndrome Alexander C Ford MD et al N Engl J Med 2017 ; 376-2566-78 DOI: 10.1056/NEJMra1607547
  4. American college of gastroenterology monograph on management of Irritable Bowel syndrome Alexander C Ford et al Am J Gastroenterol https://gi.org/wp-content/uploads/2018/07/IBS-Monograph-2018.pdf
  5. Evidence-Based Management of Irritable Bowel Syndrome With Diarrhea Mark Pimentel MD https://ajmc.s3.amazonaws.com/_media/_pdf/AJMC_A793_IBSd__Evidence%20Based%20Management%20of%20IBSd.pdf
  6. American Gastroenterological Association Institute Technical review on the Pharmacological Management of Irritable Bowel Syndrome Lin Chang et al Gastroenterology 2014 ;147:1149-1172
  7. CKS NHS Irritable Bowel Syndrome https://cks.nice.org.uk/irritable-bowel-syndrome#!scenarioRecommendation:1
  8. Irritable bowel syndrome diagnosis and management: A simplified algorithm for clinical practice Paul Moayyedi et al United European Gastroenterol J 2017 Oct 5(6);773-788 https://www.ncbi.nlm.nih.gov/pmc/articles/PMC5625880/

 

 

 

 

 

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