Crohn's Disease

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Crohn's disease\: chronic, relapsing-remitting, in
Aetiology\: unclear; inappropriate immune response to environmental trigger in genetically susceptible individuals; 15%
have a
Common sites\: 80% small bowel (terminal ileitis); 25% perianal disease.
Microscopic features\: lymphoid hyperplasia, non-caseating granulomas, transmural in
Macroscopic features\: aphthous ulcers, cobblestone appearance, bowel wall thickening,
Risk factors\: family history, smoking, previous infectious gastroenteritis, NSAID usage, diet high in re
Symptoms\: abdominal pain (right lower quadrant), diarrhoea (bloody/non-bloody), perianal pain/itching, oral ulcers,
nausea, vomiting, fever, fatigue, weight loss.
Extra-intestinal manifestations\: arthritis, episcleritis, uveitis, conjunctivitis, erythema nodosum, pyoderma gangrenosum,
PSC, fatty liver, gallstones, nephrolithiasis, anaemia, B12 de
Investigations\: FBC, LFTs, bone pro
with biopsy, upper GI endoscopy, imaging (abdominal X-ray, ultrasound, CT, MRI).
Management\:
mesalazine).
Inducing remission\: corticosteroids (prednisolone, methylprednisolone), budesonide, aminosalicylates (sulfasalazine,
Add-on treatment\: thiopurines (azathioprine, mercaptopurine), methotrexate, biologics (in
Maintaining remission\: azathioprine, mercaptopurine, methotrexate (if used for induction).
Surgery\: strictureplasty,
resection.
Complications\: psychosocial impact, intestinal strictures,
anaemia, malnutrition, delayed growth/puberty, cancer of small/large intestine.
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A comprehensive topic overview

Introduction

Crohn's disease is a chronic, relapsing-remitting, non-infectious in
It is a type of inulcerative colitis (UC).
1
Patients typically present between 20-40 years old, and Crohn's disease has an incidence of around 10-20/10000/year.
2

Aetiology

The aetiology of Crohn's disease is still unclear. However, it is thought to be an inappropriate immune response to an
environmental trigger in a genetically susceptible individual.Around 15% of a
most likely caused by a combination of genetics, environment and lifestyle factors.
3
Crohn's disease can a
1
80% of patients have evidence of small bowel disease, most commonly occurring in the distal ileum (terminal ileitis)
25% of patients su
Pathophysiology
Chronic in
macroscopically (on endoscopy).
Microscopic features
Histological features include in
granulomas. Transmural in
Macroscopic features
Initially, small super
giving the mucosa its classical cobblestone appearance, which can be seen on endoscopy. There may be bowel wall
thickening,

Risk factors

Risk factors for Crohn's disease include\:
4
Family history
Cigarette smoking
Previous infectious gastroenteritis
NSAID usage
A diet high in re

Clinical features

History
Typical symptoms of Crohn's disease include\:
1,2
Abdominal pain\: most commonly in the right lower quadrant (terminal ileum) and peri-umbilical regions
Diarrhoea\: bloody or non-bloody, may be accompanied by mucus, and nocturnal diarrhoea may occur
Perianal pain/itching\: if perianal disease
Oral ulceration (aphthous ulcers) (Figure 1)
Nausea and vomiting
Fever
Fatigue
Weight loss
Other symptoms may relate to the extra-intestinal manifestations of Crohn's disease.
5
Extra-intestinal manifestations of Crohn's disease
Extraintestinal manifestations in Crohn’s disease include\:
Musculoskeletal\: enteropathic arthritis
Eyes\: episcleritis, uveitis (Figure 2) and conjunctivitis
Skin\: erythema nodosum (Figure 3) and pyoderma gangrenosum
Hepatobiliary\: primary sclerosing cholangitis, fatty liver disease and gallstones
Renal\: nephrolithiasisHaematological\: anaemia, B12 de
Clinical examination
Typical clinical
1
Abdominal tenderness or mass
Perianal tenderness or pain, anal or perianal skin tags,
Features of anaemia (e.g. pallor, fatigue and conjunctival pallor)
Joint pain
Clubbing
Oral lesions\: aphthous ulcers
Figure 1. Oral aphthous ulceration.
6
Figure 2. Acute anterior uveitis.
7Figure 3. Erythema nodosum.
8

Di

Di
4
Ulcerative colitis
Infectious colitis
Pseudomonas colitis
Diverticular disease
Irritable bowel syndrome (this is a diagnosis of exclusion)
Radiation colitis
Crohn's disease vs. ulcerative colitis
Table 1. A summary of the key diulcerative colitis.
Crohn's disease Ulcerative colitis
Location Whole gastrointestinal tract Colon (mainly rectum)
Type of lesion Transmural in
Characteristic pattern Skip lesions Microscopic
Bowel obstruction
Complications
Fistulas
Perianal abscesses
Continuous lesions
Crypt abscesses
Friable mucosa
Gastrointestinal bleeding
Toxic megacolon
Peritonitis
AdenocarcinomaImmunosuppressants (e.g.
corticosteroids
Immunosuppressants (e.g.
corticosteroids
Treatment options
)
Aminosalicylates (e.g. mesalazine)
Antibiotics (e.g. cipro
Biologics (e.g. in
Immunomodulators (e.g. azathioprine)
Surgery (not curative)
)
Aminosalicylates (e.g. mesalazine)
Biologics (e.g. in
Surgery (curative)

Investigations

A diagnosis of Crohn's disease is made based on features of the clinical history and endoscopic
important to exclude any other causes of colitis and diarrhoea
2
Laboratory investigations
Relevant laboratory investigations include\:
1
Full blood count\: anaemia, leucocytosis, thrombocytosis
Liver function tests\: hypoalbuminaemia
Bone pro\: hypocalcaemia
Iron studies\: normal or may demonstrate iron de
Serum B12 / folate\: normal or low
In
Stool testing
Faecal calprotectin is a sensitive marker of gastrointestinal in
disease (IBD) from non-in
disease and can be used as a marker of disease activity.
Sending a stool microscopy, culture and sensitivity (MC&S) is important to exclude infection (e.g. C l o s t r i d i u m d i
Gastrointestinal endoscopy
Colonoscopy and biopsy is the preferred way to diagnose Crohn's disease. It is used to assess the colon and the terminal
ileum.
An upper gastrointestinal endoscopy is used to assess for gastroduodenal disease.
Endoscopic features of Crohn's disease
Macroscopic features of Crohn's disease on endoscopy include\:
Cobblestone appearance\: small super
Skip lesions
Oedema
Hyperaemia
Aphthous ulcers
Rose thorn ulcers\: deep penetrating linear ulcers seen around a stenosed terminal ileum.
Microscopic histology features include\:
Transmural involvement with non-caseating granulomas
Lymphoid hyperplasiaImaging
Imaging is used in acute presentations (e.g. to identify complications) and to assess the progression of Crohn's disease.
Relevant imaging investigations include\:
Abdominal X-ray\: may identify bowel dilatation and perforation in acute settings
Abdominal ultrasound\: can be used to assess bowel thickening, free-
CT abdomen\: usually used in the acute setting and to assess for complications (especially extra-mural complications)
MRI small bowel/pelvis\: can be used for ‘disease mapping’
; assesses the extent of in

Management

Management of Crohn's disease aims to induce remission and maintain remission.
9
Management plans are usually complex and require the patient to be under the care of a gastroenterologist, with the
support of specialist nurses. Treatment plans are dependent on disease severity, co-morbidities and the presence of any
complications.
Patients should be advised to stop smoking, which can reduce disease activity and the risk of complications.
Inducing remission
Initial monotherapy for inducing remission may include\:
Corticosteroids (e.g. prednisolone, methylprednisolone or intravenous hydrocortisone)\: used to induce remission in
patients with
Budesonide\: if conventional steroid use is unsuitable, however, it is less e
Aminosalicylates (e.g. sulfasalazine or mesalazine)\: these cause fewer side e
but are not as e
Add-on treatment
The following can be added to a corticosteroid after two or more exacerbations in a 12-month period or if the
corticosteroid dose cannot be reduced.
Thiopurines (e.g. azathioprine or mercaptopurine)
Methotrexate
Biologics (e.g. in
Maintaining remission
Maintenance is tailored to the individual based on side e
medications.
First-line agents to maintain remission include\:
Azathioprine
Mercaptopurine
Methotrexate can be used in patients who required it to induce remission.
Surgical management
Indications for surgical management of Crohn's disease include\:
10
Patient choice\: patients with ileocaecal disease may be o
Failure of medical management\: medications do not improve disease activity or are not suitable
Development of implications\: strictures, abscesses,
Common surgical management options for Crohn's disease include\:
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Strictureplasty\: widens narrowed areas of the bowel that could lead to obstruction
Fistula removal\: closes, opens, drains or removes a
Colectomy\: removes diseased colon, sparing the rectum
Proctocolectomy\: removes diseased colon and rectum
Ileostomy/colostomy
Bowel resection\: removal of the diseased small or large bowel and connection of the two healthy ends
Figure 4. A resected jejunum in a patient with known
Crohn's disease, demonstrating a prominent cobblestone
appearance.

Complications

Complications of Crohn's disease include\:
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Psychosocial impact (e.g. on school, work or leisure)
Intestinal complications\: strictures,
Perianal disease
Anaemia
Malnutrition, faltering growth or delayed pubertal development
Cancer of the small and large intestine

References

BMJ Best Practice. C r o h n’ s d i s e a s e . Published in 2023. Available from\: [LINK]
Ian Wilkinson. H a n d b o o k o f C l i n i c a l M e d i c i n e \: C r o h n’ s D i s e a s e . Published in 2017. Available from\: [LINK]
Crohn’s & Colitis Foundation. C a u s e s o f C r o h n’ s D i s e a s e . Published in 2023. Available from\: [LINK]
NICE. C r o h n’ s d i s e a s e . Published in 2020. Available from\: [LINK]
NICE. C r o h n’ s d i s e a s e \: W h a t a r e t h e e x t r a-i n t e s t i n a l m a n i f e s t a t i o n s o f C r o h n' s d i s e a s e ? . Published in 2020. Available from\:
[LINK]
Maksim. A p h t h o u s U l c e r . License\: [CC BY-SA]
Community Eye Health. A c u t e a n t e r i o r u v e i t i s . License\: [CC BY-NC]
Medicalpal. E r y t h e m a n o d o s u m . License\: [CC BY-SA]
NICE. C r o h n’ s d i s e a s e \: m a n a g e m e n t . Published in 2019. Available from\: [LINK]
WebMD. S u r g e r y f o r C r o h n' s D i s e a s e . Published in 2023. Available from [LINK]
NICE. W h a t a r e t h e c o m p l i c a t i o n s ? Published in 2020. Available from\: [LINK]

Reviewer

Dr Sarah Hyde
Gastroenterology registrarRelated notes
Acute Pancreatitis
Barrett’s Oesophagus
Coeliac Disease
Hyperlipidaemia
Irritable Bowel Syndrome