Crohn disease

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

Evidence last reviewed: 12 May 2026

Topic last updated: 11 Jun 2026

Crohn disease (CD) is a disorder of unknown etiology characterized by transmural inflammation of the gastrointestinal tract.

Common presenting symptoms include chronic diarrhea, weight loss, and abdominal pain.

Diagnosis is confirmed by correlating imaging, endoscopic findings, and histology, with clinical symptoms consistent with inflammatory bowel disease.

Specialist input is required from the time of diagnosis, as treatment regimens require frequent monitoring of clinical response, knowledge of common adverse events, and expertise in managing potentially serious adverse events.

The overall treatment goals are to avoid surgery and to prevent long-term complications, including cancer.

Complications include extraintestinal involvement, intestinal obstruction, abscess formation, sinuses, and fistulae.

Definition

Crohn disease (CD) is a disorder of unknown etiology characterized by transmural inflammation of the gastrointestinal (GI) tract. CD may involve any or all parts of the entire GI tract from the mouth to colon, with or without perianal involvement. CD is characterized by skip lesions (where normal bowel mucosa is found between diseased areas). The transmural inflammation often leads to fibrosis, causing intestinal obstruction. The inflammation can also result in sinus tracts that burrow through and penetrate the serosa, thereafter giving rise to perforations and fistulae.[1]

This topic covers the diagnosis and management of CD in adults.

History and exam

Key diagnostic factors

abdominal pain
prolonged diarrhea
perianal lesions

Full details

Other diagnostic factors

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

Full details

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 fiber
diet high in ultra-processed foods
use of oral contraceptives
not breastfed
use of nonsteroidal anti-inflammatory drugs (NSAIDs)

Full details

Diagnostic tests

1st tests to order

CBC
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)
fecal calprotectin
stool testing
Yersinia enterocolitica serology
ileocolonoscopy
plain abdominal x-ray
MR enterography
CT enterography

Full details

Tests to consider

ultrasonography
tissue biopsy
esophagogastroduodenoscopy
wireless capsule endoscopy

Full details

Emerging tests

serologic markers

Treatment algorithm

ACUTE

ileocecal disease not fistulizing with <100 cm of bowel affected

colonic disease not fistulizing

extensive small bowel disease (>100 cm of bowel affected) not fistulizing: initial presentation or relapse

upper gastrointestinal disease (esophageal and/or gastroduodenal disease) not fistulizing: initial presentation or relapse

perianal or fistulizing disease: initial presentation or relapse

ONGOING

in remission

Contributors

Authors

Lucy Charlotte Hicks, MBBS, PhD, FHEA, MRCP

Consultant Gastroenterologist

Department of Gastroenterology

St Mary's Hospital

Imperial College Healthcare NHS Trust

Honorary Senior Clinical Lecturer

Imperial College

London

Disclosures

LCH declares that she has no competing interests.

Georgia Woodfield, MBChB, MSc, PhD, MRCP

Consultant Gastroenterologist

Department of Gastroenterology

Royal Free Hospital

Royal Free London NHS Foundation Trust

London

Disclosures

GW has received a payment from Takeda for delivering a presentation for an IBD leadership course (Activate8).

Acknowledgements

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, and Best Practice Gastroenterology expert panel member, Dr Brooks Cash, for his contribution to this topic.

Disclosures

GR, PHP, PJS, CF, WB, BM, CT, MAP, and BC declare that they have no competing interests.

Peer reviewers

Kiron M. Das, MD, PhD, FACP, FRCP

Chief of Gastroenterology & Hepatology

Professor of Medicine

Director of Crohn's & Colitis Center of New Jersey

New Brunswick

Disclosures

KMD declares that he has no competing interests.

John Mansfield, MA, MD, FRCP

Consultant Gastroenterologist and Senior Lecturer

Royal Victoria Infirmary

Newcastle upon Tyne Hospitals NHS Foundation Trust and Newcastle University

Newcastle upon Tyne

Disclosures

JM 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

Lichtenstein GR, Loftus EV, Afzali A, et al. ACG clinical guideline: management of Crohn's disease in adults. Am J Gastroenterol. 2025 Jun 3;120(6):1225-64.Full text Abstract

Ooi CJ, Makharia GK, Hilmi I, et al. Asia Pacific consensus statements on Crohn's disease. Part 1: definition, diagnosis, and epidemiology. J Gastroenterol Hepatol. 2016 Jan;31(1):45-55.Full text Abstract

Torres J, Bonovas S, Doherty G, et al. ECCO guidelines on therapeutics in Crohn's disease: medical treatment. J Crohns Colitis. 2020 Jan 1;14(1):4-22.Full text Abstract

Adamina M, Bonovas S, Raine T, et al. ECCO guidelines on therapeutics in Crohn's disease: surgical treatment. J Crohns Colitis. 2020 Feb 10;14(2):155-68.Full text Abstract

Feuerstein JD, Ho EY, Shmidt E, et al. AGA clinical practice guidelines on the medical management of moderate to severe luminal and perianal fistulizing Crohn's disease. Gastroenterology. 2021 Jun;160(7):2496-508.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.

Differentials
- Ulcerative colitis (UC)
- Infectious colitis
- Pseudomembranous colitis
More Differentials
Guidelines
- Management of Crohn's disease in adults
- British Society of Gastroenterology guidelines on inflammatory bowel disease in adults: 2025
More Guidelines
Patient information
Crohn disease: what is it?
Crohn disease: what are the treatment options?
More Patient information
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Crohn disease

Summary

Definition

History and exam

Key diagnostic factors

Other diagnostic factors

Risk factors

Diagnostic tests

1st tests to order

Tests to consider

Emerging tests

Treatment algorithm

ileocecal disease not fistulizing with <100 cm of bowel affected

colonic disease not fistulizing

extensive small bowel disease (>100 cm of bowel affected) not fistulizing: initial presentation or relapse

upper gastrointestinal disease (esophageal and/or gastroduodenal disease) not fistulizing: initial presentation or relapse

perianal or fistulizing disease: initial presentation or relapse

in remission

Contributors

Authors

Lucy Charlotte Hicks, MBBS, PhD, FHEA, MRCP

Disclosures

Georgia Woodfield, MBChB, MSc, PhD, MRCP

Disclosures

Acknowledgements

Disclosures

Peer reviewers

Kiron M. Das, MD, PhD, FACP, FRCP

Disclosures

John Mansfield, MA, MD, FRCP

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