Irritable bowel syndrome

Overview 
Theory 
Diagnosis 
Management 
Follow up 
Resources 

Last reviewed: 14 Sep 2025

Last updated: 01 Nov 2023

Irritable bowel syndrome symptoms include recurrent abdominal pain or discomfort that is associated with a change in stool frequency or form. The pain or discomfort may be relieved by defecation.

It is important to determine whether there are any potential precipitating dietary associations such as caffeine, lactose-containing foods, or fructose-containing foods.

Examination of the abdomen is usually unremarkable. There may be mild and poorly localized tenderness in the right lower quadrant and/or left lower quadrant.

The diagnosis is based on the patient's history; there are no specific diagnostic tests. If the patient has worrying symptoms or findings such as anemia, weight loss, or fever, then these require thorough investigation.

Treatment should be individualized and is dependent on the patient's predominant symptoms.

Definition

Irritable bowel syndrome (IBS) is a chronic condition characterized by abdominal pain associated with bowel dysfunction. The pain is often relieved by defecation and is sometimes accompanied by abdominal bloating. There are no structural abnormalities to explain the pain. IBS occurs in about 15% of the adult population. The etiology is probably multifactorial, and evidence suggests motility, inflammatory, genetic, immune, psychological, and dietary components.[1]

History and exam

Key diagnostic factors

abdominal pain
alteration of bowel habits associated with pain
abdominal bloating or distension
normal exam of abdomen

Full details

Other diagnostic factors

passage of mucus with stool
urgency of defecation

Full details

Risk factors

physical and sexual abuse
posttraumatic stress disorder (PTSD)
age <50 years
female sex
previous enteric infection
family history
family and job stress

Full details

Diagnostic tests

1st tests to order

Full details

Tests to consider

fecal occult blood test
quantitative fecal immunochemical test (FIT)
serologic tests for celiac disease
fecal calprotectin
fecal lactoferrin
serum C-reactive protein (CRP)
erythrocyte sedimentation rate (ESR)
serum fibroblast growth factor 19
23‐seleno‐25‐homotaurocholic acid (SeHCAT) test
48-hour stool collection for total bile acids
empiric trial of bile acid binder
hydrogen/methane breath test
stool tests for Giardia lamblia
plain abdominal radiograph
colonoscopy
flexible sigmoidoscopy

Full details

Treatment algorithm

ONGOING

constipation-predominant

diarrhea-predominant

alternating constipation and diarrhea

Contributors

Authors

Ned Snyder, MD, MACP, AGAF

Professor of Medicine

Baylor College of Medicine and Marion DeBakey VA Hospital

Houston

Adjunct Professor of Medicine

University of Texas Medical Branch

Galveston

Disclosures

NS declares that he is a member on the board of the Kelsey Research Foundation, a non-profit organization. Kelsey Research Foundation has received and awarded private grants for the study of the microbiome in several diseases, including irritable bowel syndrome.

Peer reviewers

Douglas Drossman, MD

Professor of Medicine and Psychiatry

School of Medicine

Co-Director

UNC Center for Functional GI and Motility Disorders

Chapel Hill

Disclosures

DD declares that he has no competing interests.

Simon McLaughlin, MBBS

Research Fellow

Department of Gastroenterology

St Mark's Hospital

Northwick Park

Harrow

Disclosures

SM declares that he has no competing interests.

Horace Williams, MBBS

Clinical Research Fellow

Division of Medicine

Imperial College

London

Disclosures

HW declares that he has no competing interests.

Peer reviewer acknowledgements

BMJ Best Practice topics are updated on a rolling basis in line with developments in evidence and guidance. The peer reviewers listed here have reviewed the content at least once during the history of the topic.

Disclosures

Peer reviewer affiliations and disclosures pertain to the time of the review.

References

Our in-house evidence and editorial teams collaborate with international expert contributors and peer reviewers to ensure that we provide access to the most clinically relevant information possible.

Key articles

Longstreth GF, Thompson WG, Chey WD, et al. Functional bowel disorders. Gastroenterology. 2006 Apr;130(5):1480-91.Full text Abstract

Lacy BE, Pimentel M, Brenner DM, et al. ACG clinical guideline: management of irritable bowel syndrome. Am J Gastroenterol. 2021 Jan 1;116(1):17-44.Full text Abstract

Smalley W, Falck-Ytter C, Carrasco-Labra A, et al. AGA clinical practice guidelines on the laboratory evaluation of functional diarrhea and diarrhea-predominant irritable bowel syndrome in adults (IBS-D). Gastroenterology. 2019 Sep;157(3):851-4.Full text Abstract

Chey WD, Hashash JG, Manning L, et al. AGA clinical practice update on the role of diet in irritable bowel syndrome: expert review. Gastroenterology. 2022 May;162(6):1737-45.e5.Full text Abstract

Dionne J, Ford AC, Yuan Y, et al. A systematic review and meta-analysis evaluating the efficacy of a gluten-free diet and a low FODMAPs diet in treating symptoms of irritable bowel syndrome. Am J Gastroenterol. 2018 Sep;113(9):1290-300. Abstract

Chang L, Sultan S, Lembo A, et al. AGA clinical practice guideline on the pharmacological management of irritable bowel syndrome with constipation. Gastroenterology. 2022 Jul;163(1):118-36.Full text Abstract

Lembo A, Sultan S, Chang L, et al. AGA clinical practice guideline on the pharmacological management of irritable bowel syndrome with diarrhea. Gastroenterology. 2022 Jul;163(1):137-51.Full text Abstract

Reference articles

A full list of sources referenced in this topic is available to users with access to all of BMJ Best Practice.

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- AGA clinical practice update on the role of diet in irritable bowel syndrome: expert review
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Irritable bowel syndrome: what are the treatment options?
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Irritable bowel syndrome

Summary

Definition

History and exam

Key diagnostic factors

Other diagnostic factors

Risk factors

Diagnostic tests

1st tests to order

Tests to consider

Treatment algorithm

constipation-predominant

diarrhea-predominant

alternating constipation and diarrhea

Contributors

Authors

Ned Snyder, MD, MACP, AGAF

Disclosures

Peer reviewers

Douglas Drossman, MD

Disclosures

Simon McLaughlin, MBBS

Disclosures

Horace Williams, MBBS

Disclosures

Peer reviewer acknowledgements

Disclosures

References

Key articles

Reference articles

A full list of sources referenced in this topic is available to users with access to all of BMJ Best Practice.

Differentials

Guidelines

Patient information

Log in or subscribe to access all of BMJ Best Practice

Log in or subscribe to access all of BMJ Best Practice

Log in to access all of BMJ Best Practice