Irritable bowel syndrome (IBS) is a chronic condition that is very common in North America and Europe. It is thought that the underlying pathophysiology involves changes in gastrointestinal motility, visceral hypersensitivity, and altered gastrointestinal permeability. Patients present with recurrent abdominal pain associated with changes in stool frequency, form, and/or appearance. IBS is a clinical diagnosis based on the and ruling out alternative diagnoses. Nonpharmacological treatment includes dietary modifications (e.g., avoidance of trigger foods) and psychobehavioral therapies. Pharmacological therapies such as loperamide, laxatives, and lubiprostone are targeted to diarrhea, constipation, and global IBS symptoms, respectively.
- Prevalence: 10–20% in North America and Europe (accounts for 20–50% of referrals to gastroenterologists)
- Sex: : In Western countries, women are 1.5–2 times more likely to be affected than men.
- Age: highest prevalence in individuals aged 20–39 
- Associated conditions 
Epidemiological data refers to the US, unless otherwise specified.
IBS is a functional gastrointestinal disorder without a specific organic cause. The pathophysiological processes leading to IBS are multifaceted and not yet fully understood. The most common findings associated with IBS are:
- Altered gastrointestinal motility
- Visceral hypersensitivity/hyperalgesia
- Altered permeability of the gastrointestinal mucosa
- Psychosocial aspects
- Frequency, intensity, and localization generally vary widely from patient to patient
- Typically related to defecation
- Altered bowel habits: : diarrhea and/or constipation
- Other gastrointestinal symptoms
- Extraintestinal symptoms
- Physical examination: normal
- Evaluate for .
- Screen for red flag symptoms (see “Clinical features”).
- Obtain a limited diagnostic workup to rule out alternative diagnoses.
Rome IV criteria for irritable bowel syndrome 
All of the following criteria must be met to diagnose IBS.
- Timing: ≥ 6 months since the onset of symptoms
Laboratory studies 
The following studies should routinely be considered to rule out alternative etiologies :
- All patients: CBC (anemia requires further evaluation)
In patients with diarrhea
- CRP and
- Stool testing for 
- In patients with relevant symptoms and history
- Only recommended in patients:
- Due for age-appropriate 
|Overview of common differential diagnoses|
|Condition||General appearance||Pain||Stool habits|
|Irritable bowel syndrome|| || |
|Crohn disease|| || |
|Ulcerative colitis|| || || |
|Colorectal carcinoma|| || |
Other differential diagnoses to consider
- Bacterial or viral gastroenteritis
- Bacterial overgrowth syndrome (i.e., )
- See also: “Differential diagnoses of acute abdominal pain”
- See also: “Causes of chronic diarrhea”
- See also: “Causes of constipation”
The differential diagnoses listed here are not exhaustive.
Currently, there are no curative treatments for IBS. Management is focused on treating the associated symptoms.
Nonpharmacological treatment 
- Dietary adjustments
Lifestyle changes 
- Regular physical activity
- Stress management (e.g., relaxation techniques)
- Psychobehavioral therapy 
- Adjunctive therapy: peppermint oil for global symptom relief 
Elimination diets that restrict fermentable oligosaccharides, disaccharides, monosaccharides, and polyols (i.e., a low FODMAP diet) should be undertaken with the support of a registered dietitian in order to avoid nutritional deficiencies. 
- Evidence for pharmacological therapy is mixed and recommendations vary between guidelines.
- Consult a specialist for refractory symptoms and/or long-term treatment.
- Alternative medications: include alosetron (a selective 5-HT3 receptor antagonist), eluxadoline (opioid agonist/antagonist)
- Polyethylene glycol (PEG) 
- Alternative medications:
Abdominal pain 
The following can be considered to treat associated abdominal pain:
- Antispasmodics: e.g., dicyclomine, hyoscyamine
- Tricyclic antidepressants: e.g., amitriptyline (off-label) 
- IBS may be managed in an outpatient setting; arrange for close follow-up.
- Provide patients with alarm features develop (see “Clinical features”). if