Irritable bowel syndrome

Last updated: September 20, 2023

Summarytoggle arrow icon

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 Rome IV criteria for IBS 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.

Epidemiologytoggle arrow icon


Epidemiological data refers to the US, unless otherwise specified.

Pathophysiologytoggle arrow icon

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


Clinical featurestoggle arrow icon

IBS is characterized by chronic abdominal pain and changes in bowel habits (see also “Rome IV criteria for IBS”).

Red flag symptoms: nighttime diarrhea and abdominal pain, fever, bloody stools, weight loss, and acute onset of symptoms.

Classificationtoggle arrow icon

Several subtypes of IBS exist and are defined by stool quality. [6]

Diagnosticstoggle arrow icon

IBS is a clinical diagnosis (using the Rome IV criteria for IBS). Limited diagnostic studies are recommended for the primary purpose of ruling out alternative diagnoses.

Approach [6]

An acute change in bowel habits, signs of overt GI bleeding, or other red flags for CRC should prompt further diagnostic evaluation.

Rome IV criteria for irritable bowel syndrome [7]

All of the following criteria must be met to diagnose IBS.

  • Timing: ≥ 6 months since the onset of symptoms
  • Symptoms
    • Recurrent abdominal pain (≥ 1 day per week during the previous 3 months)
    • PLUS ≥ 2 of the following
      • Abdominal pain related to defecation
      • Change in stool frequency
      • Change in appearance of stool

Laboratory studies [6][8]

The following studies should routinely be considered to rule out alternative etiologies :

Colonoscopy [8]

Differential diagnosestoggle arrow icon

Overview of common differential diagnoses
Condition General appearance Pain Stool habits
Irritable bowel syndrome
  • Healthy; no weight loss
  • Alleviated by defecation; diffuse; no nighttime pain
Crohn disease
  • Usually constant; occurs particularly in the right lower abdomen; may appear at night
Ulcerative colitis
  • Weight loss only in severe cases
  • Mostly left lower abdomen; may occur at night
Colorectal carcinoma
  • Weight loss

Other differential diagnoses to consider

The differential diagnoses listed here are not exhaustive.

Treatmenttoggle arrow icon

Currently, there are no curative treatments for IBS. Management is focused on treating the associated symptoms.

Nonpharmacological treatment [8]

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. [8]

Pharmacotherapy [8]

  • Evidence for pharmacological therapy is mixed and recommendations vary between guidelines.
  • Consult a specialist for refractory symptoms and/or long-term treatment.

Diarrhea [11]

When treating IBS-associated diarrhea, use caution to avoid constipation as an adverse effect, especially in patients with IBS-M or IBS-U.

Constipation [12]

Abdominal pain [8][11][12]

The following can be considered to treat associated abdominal pain:

Disposition [13]

  • IBS may be managed in an outpatient setting; arrange for close follow-up.
  • Provide patients with return precautions if alarm features develop (see “Clinical features”).

Referencestoggle arrow icon

  1. Camilleri M. Diagnosis and Treatment of Irritable Bowel Syndrome. JAMA. 2021; 325 (9): p.865.doi: 10.1001/jama.2020.22532 . | Open in Read by QxMD
  2. Wilkins T, Pepitone C, Alex B, Schade RR. Diagnosis and management of IBS in adults. Am Fam Physician. 2012; 86 (5): p.419-426.
  3. Chey WD, Kurlander J, Eswaran S. Irritable bowel syndrome: a clinical review.. JAMA. 2015; 313 (9): p.949-58.doi: 10.1001/jama.2015.0954 . | Open in Read by QxMD
  4. Canavan C, West J, Card T. The epidemiology of irritable bowel syndrome. Clin Epidemiol. 2014; 6: p.71-80.doi: 10.2147/CLEP.S40245 . | Open in Read by QxMD
  5. Camilleri M, Lasch K, Zhou W. Irritable Bowel Syndrome: Methods, Mechanisms, and Pathophysiology. The confluence of increased permeability, inflammation, and pain in irritable bowel syndrome. American Journal of Physiology. 2012; 303 (7): p.775-785.doi: 10.1152/ajpgi.00155.2012 . | Open in Read by QxMD
  6. Thabane M, Marshall JK. Post-infectious irritable bowel syndrome. World J Gastroenterol. 2009; 15 (29): p.3591-3596.
  7. Lacy BE, Mearin F, Chang L, et al. Bowel Disorders. Gastroenterology. 2016; 150 (6): p.1393-1407.e5.doi: 10.1053/j.gastro.2016.02.031 . | Open in Read by QxMD
  8. Lacy BE, Pimentel M, Brenner DM, et al. ACG Clinical Guideline: Management of Irritable Bowel Syndrome. Am J Gastroenterol. 2020; 116 (1): p.17-44.doi: 10.14309/ajg.0000000000001036 . | Open in Read by QxMD
  9. Smalley W, Falck-Ytter C, Carrasco-Labra A, Wani S, Lytvyn L, Falck-Ytter Y. AGA Clinical Practice Guidelines on the Laboratory Evaluation of Functional Diarrhea and Diarrhea-Predominant Irritable Bowel Syndrome in Adults (IBS-D). Gastroenterology. 2019; 157 (3): p.851-854.doi: 10.1053/j.gastro.2019.07.004 . | Open in Read by QxMD
  10. Moayyedi P, Andrews CN, MacQueen G, et al. Canadian Association of Gastroenterology Clinical Practice Guideline for the Management of Irritable Bowel Syndrome (IBS). J Can Assoc Gastroenterol. 2019; 2 (1): p.6-29.doi: 10.1093/jcag/gwy071 . | Open in Read by QxMD
  11. Lembo A, Sultan S, Chang L, Heidelbaugh JJ, Smalley W, Verne GN. AGA Clinical Practice Guideline on the Pharmacological Management of Irritable Bowel Syndrome With Diarrhea. Gastroenterology. 2022; 163 (1): p.137-151.doi: 10.1053/j.gastro.2022.04.017 . | Open in Read by QxMD
  12. Chang L, Sultan S, Lembo A, Verne GN, Smalley W, Heidelbaugh JJ. AGA Clinical Practice Guideline on the Pharmacological Management of Irritable Bowel Syndrome With Constipation. Gastroenterology. 2022; 163 (1): p.118-136.doi: 10.1053/j.gastro.2022.04.016 . | Open in Read by QxMD
  13. Walls R, Hockberger R, Gausche-Hill M, Erickson TB, Wilcox SR. Rosen's Emergency Medicine 10th edition- Concepts and Clinical Practice E-Book. Elsevier Health Sciences ; 2022

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