11/14/24, 10\:59 AM Irritable Bowel Syndrome

Irritable Bowel Syndrome

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Irritable bowel syndrome (IBS)\: chronic condition with ≥6 months of abdominal pain/discomfort, bloating, or altered bowel
habits; diagnosis of exclusion.
Aetiology\: unknown; involves disordered gut-brain axis, visceral hypersensitivity, abnormal motility, and altered microbiota.
Risk factors\: age \<50, female sex, mental health history, recent gastroenteritis, family history.
Clinical features\: abdominal pain, bloating, change in bowel habit, worsened by eating, improved by defecation, with non-
speci
Red
Investigations\: FBC, CRP, TFTs, IgA-tTG for coeliac, CA-125 if bloating; stool tests (FIT, calprotectin).
Diagnosis\: Rome IV criteria - ≥1 day/week of pain, related to defecation, stool frequency/form change; IBS subtypes
include IBS-Diarrhoea, IBS-Constipation, IBS-Mixed, IBS-Unclassi
Management\: lifestyle changes (exercise, stress management, dietary advice), low FODMAP diet, probiotics, subtype-
speci
refractory cases.
Complications\: no direct complications, but straining/constipation may lead to haemorrhoids or anal
new symptoms arise.
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A comprehensive topic overview

Introduction

Irritable bowel syndrome (IBS) is de
bloating in the absence of other red
1
It is very common among adults and children, with up to 20% of the population being a2
It is a poorly understood
condition but recently more evidence has emerged for the role of the gut-brain axis and for various treatments.
3

Aetiology

The exact cause of IBS is unknown, and it is grouped with other functional disorders (e.g.
dyspepsia), which do not have a measurable pathological hallmark or biomarker. However, advances in research have
uncovered several proposed contributing mechanisms, which include\:
3-4
Disordered gut-brain axis function, which links bowel symptoms to stress hormones and psychosocial factors
Visceral hypersensitivity, whereby there is an exaggerated response of the bowel to certain stimuli (e.g. food)
Abnormal gut motility, which can either lead to decreased or increased colonic transit time (causing constipation or
diarrhoea, respectively)
Peripheral bowel factors include alterations in gut microbiota (contributing to post-gastroenteritis IBS) and immune-
mediated processes
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Risk factors

Certain risk factors have been linked with an increased risk of developing IBS\:
5
Age\: typically occurs in younger people and is rare to diagnose >50 years old
Gender\: more common in females
Mental health history\: those with anxiety, depression, or a history of childhood abuse have a higher risk of developing
IBS
Recent gastroenteritis\: can lead to post-infectious IBS, impacted by the duration/type of infection and whether
antibiotics were used
Family history\: genetic predisposition to developing IBS

Clinical features

History

The symptoms of IBS cross over with other serious gastrointestinal (GI) conditions such as bowel cancer and in
bowel disease (IBD), and therefore, a careful history is required.
IBS should be suspected in those with at least 6 months of\:
1
Abdominal pain, or
Bloating, or
Change in bowel habit
Other suggestive features of IBS include\:
Symptoms worsened by eating
Symptoms improved by defecation
Dietary factors (e.g. worsening symptoms with alcohol, ca
Tenesmus-like symptoms (e.g. straining, urgency, incomplete evacuation)
Rectal mucus
Non-speci
Red
IBS should not present with red
investigation\:
Rectal bleeding
Weight loss (unexplained)
Age >50 years
Family history of bowel/ovarian cancer, in
Abdominal/rectal mass
Signi
Iron de
Stigmata of bowel cancer or in
It is important to explore possible triggers and psychosocial history, including\:
Concurrent mental health history (e.g. mood disturbance, anxiety)
Work, home life and stress/sleep
Alcohol, smoking, drug use and other medications used (e.g. laxatives)
Impact of symptoms on activities of daily living
Recent GI infection or antibiotic use
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Clinical examination

Abdominal examination should be carried out in all those with suspected IBS to aid the exclusion of other organic causes.
A rectal examination should be o
Those with IBS usually have minimal abdominal tenderness, which is more generalised rather than focal.

Di

IBS can mimic symptoms of almost any gastrointestinal condition. The two important di
malignancy and in
6
Bowel cancer\: should always be considered, especially for patients aged >60 years with a change in bowel habit
Ovarian cancer\: in women with unexplained bloating, particularly if aged over 50, should also be considered
Upper gastrointestinal cancer\: (oesophageal/gastric) can also cause IBS-like symptoms at an early stage before the
onset of classic symptoms like dysphagia
Inulcerative colitis (UC) or Crohn’s disease, which have a bimodal distribution, with a
peak between the ages of 20-30 and another between 60-70 years old
Other di
Coeliac disease\: causing diarrhoea and steatorrhea
Microscopic colitis\: autoimmune-mediated or related to medications such as non-steroidal anti-in
or proton pump inhibitors (PPIs) causing watery diarrhoea
Bile acid malabsorption\: occurs after cholecystectomy or hemicolectomy, which prevents bile acids from being
reabsorbed, causing diarrhoea
Gastrointestinal infection with subsequent lactose intolerance or antibiotic-associated diarrhoea
Other gastroenterological conditions, e.g. diverticular disease, gallstones, dyspepsia
Other non-GI conditions which can alter bowel habits or cause abdominal pain/bloating include\:
Ovarian cyst or endometriosis
Hypo/hyperthyroidism
Liver disease
Anxiety/depression/pre-menstrual syndrome

Investigations

Laboratory investigations

Blood and stool tests should be carried out to exclude other causes such as malignancy, IBD or coeliac disease.
7, 8
Blood tests
Full blood count\: to exclude anaemia, raised white cell count or platelets indicating in
C-reactive protein\: elevated in in
Thyroid function tests\: to exclude thyroid disease
IgA tissue transglutaminase (TTG)\: for Coeliac disease
CA-125\: for women (especially >50 years old) with persistent bloating or abdominal symptoms
Iron studies\: if anaemic, as iron-de
Stool tests
Faecal immunohistochemical test (FIT)\: if positive, refer urgently for suspected colorectal cancer
Faecal calprotectin\: raised in in
Stool microscopy, culture and sensitivity (MC&S)\: to exclude bacterial infection in diarrhoea
H . p y l o r i faecal antigen test\: if re
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Diagnosis

If alternative diagnoses are excluded and no red
primary care.
1
The ROME-IV criteria is a more restrictive framework, used mostly in secondary care, to make a diagnosis of IBS. 3, 9
consists of recurrent abdominal pain ≥1 day/week in the last 3 months (on average) with ≥2 of the following\:
This
Symptoms related to defecation
Associated with change in stool frequency
Associated with change in stool form
The ROME-IV criteria can also categorise IBS into di

IBS subtypes

Using the above criteria and the Bristol stool chart, IBS can be sub-classi
IBS-D (IBS with diarrhoea)\: >25% type 6-7 stools and \<25% type 1-2 stools
IBS-C (IBS with constipation)\: >25% type 1-2 stools and \<25% type 6-7 stools
IBS-M (IBS with mixed bowel habits)\: >25% type 1-2 stools and type 6-7 stools
IBS-U (unclassi
Figure 1. The Bristol Stool Chart

Management

Management should begin with an explanation of the diagnosis, reassurance that other causes have been excluded, and a
discussion about managing IBS and its focus on improving symptoms.

Lifestyle

Changes to lifestyle factors, especially in diet, are central to managing IBS.
Non-dietary advice
Regular exercise (>150 minutes of moderate-intensity aerobic activity per week)
Improvements in sleep, stress and mood
The IBS Network provides good information and support for patients
Dietary advice
Basic dietary advice includes\:
10
Regular small meals, aiming for a healthy balanced diet, limiting processed foods and focusing on homemade meals
with fresh ingredients
Avoid eating too quickly, eating late at night or missing meals
Reduce spicy food or high-fat processed foods (e.g. fried food, pastries)
Increase water intake (1.5-2 L of water a day)
Avoid excess ca
days)
Limiting dietary
IBS-C (gradually increase
11
Low FODMAP diet
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The low FODMAP diet restricts types of carbohydrates called FODMAPS (fermentable oligosaccharides, di-
saccharides, mono-saccharides, and polyols). 12
These foods are poorly absorbed and remain in the large bowel to
ferment, contributing to water balance changes and excess gas production, which those with IBS are more sensitive
to.
The diet should be initially tried for 4-6 weeks and supervised by a dietitian.
Probiotics (and prebiotics) have limited evidence in IBS but may have a role as more research occurs\:
13
Probiotics\: good gut bacteria found in foods or supplements that can improve the balance and diversity of di
bacteria to improve digestion and symptoms of IBS. Patients should be advised to continue for 12 weeks before
discontinuing if there is no improvement in symptoms.
Prebiotics\: foods (e.g. onions, garlic, asparagus) which feed good gut bacteria and may have similar bene
digestion

Medical

Medications can be used in IBS and depends on the speci
3, 14-15
IBS-C (with constipation)
Laxatives are indicated\:
Bulk-forming laxatives (e.g. ispaghula husk)
Osmotic laxatives (e.g. macrogols)
Stimulant laxatives (e.g. senna)
Avoid lactulose as it increases gas production and can worsen IBS symptoms.
If di
should be considered. Linaclotide is a newer treatment that softens stool and increases gut transit time.
IBS-D (with diarrhoea)
Antimotility agents are indicated\:
Loperamide\: this should be reviewed after 3 months and discontinued if no bene
Abdominal pain/cramps
A variety of antispasmodic agents can aid GI smooth muscle relaxation and are usually well tolerated\:
Mebeverine
Hyoscine butylbromide (Buscopan®)
Alverine
Peppermint oil
If antispasmodics are ine
Amitriptyline\: if no improvement with antispasmodics after 3 months
Selective serotonin reuptake inhibitors (SSRIs)\: if no response to amitriptyline after 6 months

Psychological

If IBS symptoms have been refractory to drug treatment for more than 12 months, referral to IBS-speci
behavioural therapy (CBT) should be considered.
Other treatments, like hypnotherapy and relaxation therapy, may help, but no clear evidence exists.

Complications

IBS is a chronic illness with a
progression.
Lower GI conditions such as anal and haemorrhoids can occur from straining/constipation related to IBS.
It is important to remember that if new symptoms occur in the context of known IBS, organic pathology must still be
assessed for and excluded.
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References

NICE CKS. I r r i t a b l e b o w e l s y n d r o m e \: W h e n s h o u l d I s u s p e c t i r r i t a b l e b o w e l s y n d r o m e ? 2023. Available from\: [LINK].
York and Scarborough Teaching Hospitals NHS Foundation Trust. I r r i t a b l e b o w e l s y n d r o m e ( I B S ) - I n f o r m a t i o n f o r p a t i e n t s ,
r e l a t i v e s a n d c a r e r s . 2022. Available from\: [LINK].
Vasant DH, Paine PA, Black CJ, et al. B r i t i s h S o c i e t y o f G a s t r o e n t e r o l o g y g u i d e l i n e s o n t h e m a n a g e m e n t o f i r r i t a b l e b o w e l
s y n d r o m e . Gut. 2021. Available from\: [LINK].
Wang K, Liu H, Liu J, et al. F a c t o r s r e l a t e d t o i r r i t a b l e b o w e l s y n d r o m e a n d d i
s t u d y i n t h e U K B i o b a n k . Frontiers in Pharmacology. (2022). Available from\: [LINK].
Health Match. I B S \: C a u s e s , R i s k F a c t o r s , S i g n s , A n d S y m p t o m s . 2021. Available from\: [LINK].
NICE CKS. I r r i t a b l e b o w e l s y n d r o m e . W h a t e l s e c o u l d i t b e ? 2023. Available from\: [LINK].
BMJ Best Practice. I r r i t a b l e b o w e l s y n d r o m e . 2024. Available from\: [LINK].
NICE CKS. I r r i t a b l e b o w e l s y n d r o m e . A s s e s s m e n t . 2023. Available from\: [LINK].
MDCALC. R o m e I V D i a g n o s t i c C r i t e r i a f o r I r r i t a b l e B o w e l S y n d r o m e ( I B S ) . Available from\: [LINK].
British Dietary Association (BDA). I r r i t a b l e b o w e l s y n d r o m e ( I B S ) a n d d i e t . Available from\: [LINK].
Milton Keynes University Hospital NHS Foundation Trust. A s e l f –h e l p G u i d e f o r P e o p l e w i t h I r r i t a b l e B o w e l S y n d r o m e .
Available from\: [LINK].
Gloucestershire Hospitals NHS Foundation Trust. I B S a n d t h e l o w F O D M A P d i e t . Available from\: [LINK].
British Dietary Association (BDA). P r o b i o t i c s a n d g u t h e a l t h . Available from\: [LINK].
NICE CKS. I r r i t a b l e b o w e l s y n d r o m e . M a n a g e m e n t o f i r r i t a b l e b o w e l s y n d r o m e . 2023. Available from\: Guts UK. I r r i t a b l e B o w e l S y n d r o m e ( I B S ) . Available from\: [LINK].
[LINK].

Reviewer

Dr Katie Sissons
General Practitioner

Related notes

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Contents

Introduction
Aetiology
Risk factors
Clinical features
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Di
Investigations
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