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Irritable bowel syndrome

Background

Overview

Definition
IBS is a functional gastrointestinal disorder characterized by recurrent abdominal pain and altered bowel habits (constipation, diarrhea or both), often with associated bloating.
1
Pathophysiology
The etiology of IBS is poorly understood. Potential etiological mechanisms include genetic factors (most notably an identified mutation of SCN5A); post-infectious changes, chronic infections and disturbances in the intestinal microbiota; low-grade mucosal inflammation, immune activation, and altered intestinal permeability; disordered bile salt metabolism (in 10-20% of patients with diarrhea); abnormalities in serotonin metabolism; and alterations in brain function.
1
Epidemiology
In the US, the incidence of IBS is estimated at 196 cases per 100,000 person-years, with an estimated prevalence of 5-12% based on Rome II criteria.
2
Disease course
Key clinical manifestations include abdominal pain or discomfort, bloating, diarrhea, and constipation.
3
Prognosis and risk of recurrence
There is no evidence that IBS is associated with an increased risk of mortality. However, patients with IBS exhibit a poorer QoL and utilize the healthcare system to a greater degree than patients without the diagnosis.
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Guidelines

Key sources

The following summarized guidelines for the evaluation and management of irritable bowel syndrome are prepared by our editorial team based on guidelines from the American Gastroenterological Association (AGA 2024,2022,2020,2012), the European Society for Paediatric Gastroenterology Hepatology and Nutrition (ESPGHAN 2023), the United European Gastroenterology (UEG/ESPEN 2023), the American College of Gastroenterology (ACG 2021), the British Society of Gastroenterology (BSG 2021), ...
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Screening and diagnosis

Diagnosis
As per ACG 2021 guidelines:
Adopt a positive diagnostic strategy over diagnostic strategy of exclusion to improve cost-effectiveness in patients with symptoms of IBS.
A
Consider adopting a positive diagnostic strategy over diagnostic strategy of exclusion to improve time to initiate appropriate therapy in patients with symptoms of IBS.
E
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Classification and risk stratification

Classification
As per ACG 2021 guidelines:
Consider categorizing patients based on an accurate IBS subtype to improve patient therapy:
Situation
Guidance
IBS-C
> 25% of bowel movements with Bristol stool scale types 1-2 and < 25% with types 6-7
IBS-D
> 25% of bowel movements with Bristol stool scale types 6-7 and < 25% with types 1-2
IBS-M
> 25% of bowel movements with Bristol stool scale types 1-2 and > 25% with types 6-7
IBS-U
Meets diagnostic criteria for IBS but bowel habits not accurately categorized in any of the subtypes
E
Recognize that Bristol stool scale categorizes stool appearance into the following types:
Situation
Guidance
Type 1
Separate hard lumps, like nuts (hard to pass)
Type 2
Sausage-shaped but lumpy
Type 3
Like a sausage but with cracks on its surface
Type 4
Like a sausage or snake, smooth and soft
Type 5
Soft blobs with clear cut edges (passed easily)
Type 6
Fluffy pieces with ragged edges, a mushy stool
Type 7
Watery, no solid pieces (entirely liquid)

Diagnostic investigations

Laboratory tests: as per ACG 2021 guidelines, consider obtaining CRP to rule out IBD in patients with suspected IBS and diarrhea symptoms without alarm features.
B
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  • Breath testing

  • Diagnostic imaging

  • Evaluation for bile acid diarrhea

  • Evaluation for pancreatic insufficiency

Diagnostic procedures

Colonoscopy: as per ACG 2021 guidelines, do not perform routine colonoscopy in < 45 years old patients with symptoms of IBS without warning signs.
D

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  • Anorectal physiology testing

Medical management

Antispasmodics: as per AGA 2022 guidelines, consider offering antispasmodics in patients with IBS.
C

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  • Antidepressants (TCAs)

  • Antidepressants (SSRIs)

  • Probiotics

  • Management of diarrhea (eluxadoline)

  • Management of diarrhea (rifaximin)

  • Management of diarrhea (5-HT3 antagonists)

  • Management of diarrhea (loperamide)

  • Management of diarrhea (bile acid sequestrants)

  • Management of constipation

  • Management of constipation (5-HT4 agonists)

  • Management of constipation (guanylate cyclase activators)

  • Management of constipation (lubiprostone)

  • Management of constipation (tenapanor)

Nonpharmacologic interventions

Exercise: as per BSG 2021 guidelines, advise all patients with IBS to take regular exercise.
B

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  • Dietary modifications

  • Peppermint oil

  • Psychotherapy

  • Herbal products

  • Acupuncture

Therapeutic procedures

Fecal microbiota transplantation: as per AGA 2024 guidelines, avoid offering conventional fecal microbiota transplantation in adult patients with IBS outside of clinical trials.
D

Specific circumstances

Patients with obesity: as per ESPEN/UEG 2023 guidelines, obtain an assessment of nutritional status (for malnutrition, sarcopenia, overweight, obesity) at the time of diagnosis and regularly thereafter (at least once a year) in patients with IBS.
B
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Patient education

General counseling: as per BSG 2021 guidelines, educate patients about the diagnosis of IBS, its underlying pathophysiology and the natural history of the condition, including common symptom triggers. Introduce the concept of IBS as a disorder of gut-brain interaction, together with a simple account of the gut-brain axis and how this is impacted by diet, stress, cognitive, behavioral and emotional responses to symptoms, and postinfectious changes.
B
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Follow-up and surveillance

Indications for referral: as per BSG 2021 guidelines, refer to gastroenterology in secondary care in case of diagnostic doubt, in patients with severe or refractory to first-line therapy symptoms, or if the patient requests a specialist opinion.
B

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  • Management of refractory disease