Irritable bowel syndrome

Last reviewed: 1 Mar 2023
Last updated: 10 Feb 2023



History and exam

Key diagnostic factors

  • presence of risk factors
  • abdominal pain
  • alteration of bowel habits associated with pain
  • abdominal bloating or distension
  • normal examination of abdomen
More key diagnostic factors

Other diagnostic factors

  • passage of mucus with stool
  • urgency of defecation
Other diagnostic factors

Risk factors

  • physical and sexual abuse
  • post-traumatic stress disorder (PTSD)
  • age <50 years
  • female sex
  • previous enteric infection
  • family history
  • family and job stress
More risk factors

Diagnostic investigations

1st investigations to order

  • FBC
More 1st investigations to order

Investigations to consider

  • faecal occult blood test
  • serologic tests for coeliac disease
  • faecal calprotectin
  • faecal 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 x-ray
  • colonoscopy
  • flexible sigmoidoscopy
More investigations to consider

Treatment algorithm




alternating constipation and diarrhoea



Ned Snyder, MD, MACP, AGAF

Chief of Gastroenterology and Hepatology

Kelsey-Seybold Clinic

Clinical Professor of Medicine

Baylor College of Medicine


Adjunct Professor of Medicine

University of Texas Medical Branch




NS declares that he is on the board of the Kelsey Research Foundation, a non-profit organisation that sponsors research in the intestinal microbiome; he does not receive direct or indirect compensation. NS received a grant from the State of Texas to study genetic factors in the development of hepatocellular cancer in Hispanic people.

Peer reviewers

Douglas Drossman, MD

Professor of Medicine and Psychiatry

School of Medicine


UNC Center for Functional GI and Motility Disorders

Chapel Hill



DD declares that he has no competing interests.

Simon McLaughlin, MBBS

Research Fellow

Department of Gastroenterology

St Mark's Hospital

Northwick Park




SM declares that he has no competing interests.

Horace Williams, MBBS

Clinical Research Fellow

Division of Medicine

Imperial College




HW declares that he has no competing interests.

  • Differentials

    • Crohn's disease
    • Ulcerative colitis
    • Lymphocytic and collagenous colitis (microscopic colitis)
    More Differentials
  • Guidelines

    • AGA clinical practice guideline on the pharmacological management of irritable bowel syndrome with constipation
    • AGA clinical practice update on the role of diet in irritable bowel syndrome: expert review
    More Guidelines
  • Patient leaflets

    Irritable bowel syndrome: what is it?

    Irritable bowel syndrome: what treatments work?

    More Patient leaflets
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