Irritable bowel syndrome

Last reviewed: 5 Jan 2023
Last updated: 12 Apr 2022



History and exam

Key diagnostic factors

  • abdominal discomfort
  • alteration of bowel habits associated with pain
  • abdominal bloating or distention
  • normal exam 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
  • PTSD
  • age <50 years
  • female sex
  • previous enteric infection
  • family history
  • family and job stress
More risk factors

Diagnostic investigations

1st investigations to order

  • CBC
More 1st investigations to order

Investigations to consider

  • fecal occult blood test
  • 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
More investigations to consider

Treatment algorithm




alternating constipation and diarrhea



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 organization 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 disease
    • Ulcerative colitis
    • Lymphocytic and collagenous colitis (microscopic colitis)
    More Differentials
  • Guidelines

    • American Society for Gastrointestinal Endoscopy guideline on informed consent for GI endoscopic procedures
    • ACG clinical guideline: management of irritable bowel syndrome
    More Guidelines
  • Patient leaflets

    Irritable bowel syndrome: what is it?

    Irritable bowel syndrome: what treatments work?

    More Patient leaflets
  • padlock-lockedLog in or subscribe to access all of BMJ Best Practice

Use of this content is subject to our disclaimer