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Last reviewed: 25 Mar 2025
Last updated: 11 Apr 2025

Summary

Definition

History and exam

Key diagnostic factors

  • presence of risk factors
  • abdominal pain
  • prolonged diarrhoea
  • perianal lesions

Other diagnostic factors

  • bowel obstruction
  • blood in stools
  • fatigue
  • abdominal tenderness
  • weight loss
  • fever
  • oral lesions
  • abdominal mass
  • extra-intestinal manifestations (e.g., erythema nodosum or pyoderma gangrenosum)

Risk factors

  • white ethnicity
  • Ashkenazi Jewish ancestry
  • age 15-40 or 50-60 years
  • family history of CD
  • use of antibiotics
  • cigarette smoking
  • diet high in refined sugar
  • diet low in fibre
  • diet high in ultra-processed foods
  • use of oral contraceptive pill
  • not breastfed
  • use of non-steroidal anti-inflammatory drugs (NSAIDs)

Diagnostic investigations

1st investigations to order

  • FBC
  • iron studies (serum iron, serum ferritin, total iron binding capacity [TIBC], transferrin saturation)
  • serum vitamin B12
  • serum folate
  • comprehensive metabolic panel (CMP)
  • CRP and erythrocyte sedimentation rate (ESR)
  • stool testing
  • Yersinia enterocolitica serology
  • plain abdominal x-ray
  • MRI abdomen/pelvis
  • CT abdomen

Investigations to consider

  • abdominal and pelvic ultrasonography
  • ileocolonoscopy
  • tissue biopsy
  • oesophagogastroduodenoscopy
  • wireless capsule endoscopy
  • faecal calprotectin

Emerging tests

  • serological markers

Treatment algorithm

Contributors

Authors

Consultant Gastroenterologist

Department of Gastroenterology

St Mary's Hospital

Imperial College Healthcare NHS Trust

Honorary Senior Clinical Lecturer

Imperial College

London

UK

Disclosures

LCH declares that she has no competing interests.

Specialist Registrar in Gastroenterology and General Medicine

Imperial College Healthcare NHS Trust

Research Fellow

Imperial College London

London

UK

Disclosures

GW declares that she has no competing interests.

Dr Georgia Woodfield and Dr Lucy Charlotte Hicks would like to gratefully acknowledge Mr George Reese, Dr Pranav H. Patel, Dr Philip J. Smith, Dr Charlotte Ford, Dr Wissam Bleibel, Dr Bishal Mainali, Dr Chandrashekhar Thukral, and Dr Mark A. Peppercorn, the previous contributors to this topic.

Disclosures

GR is an author of a number of references cited in this topic. PHP, PJS, CF, WB, BM, CT, and MAP declare that they have no competing interests.

Peer reviewers

Chief of Gastroenterology & Hepatology

Professor of Medicine

Director of Crohn's & Colitis Center of New Jersey

New Brunswick

NJ

Disclosures

KMD declares that he has no competing interests.

Consultant Gastroenterologist and Senior Lecturer

Royal Victoria Infirmary

Newcastle upon Tyne Hospitals NHS Foundation Trust and Newcastle University

Newcastle upon Tyne

UK

Disclosures

JM declares that he has no competing interests.

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