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Crohn's Disease

1. Definition

2. Epidemiology

• More common in those of European origin and Western societies
• Incidence - 5-10 new cases/100,000 per year
• Prevalence - 50-100/100,000
• Can affect any age group. Bimodal distribution - first largest peak at 15-30, next smaller peak at 60-80.

3. Risk Factors

• Exact aetiology is unknown - many theories including genetic, infective, environmental and immunological causes.
• Smoking increases risk
• Family history

4. Symptoms and Signs

• Many patients have had symptoms for years before presentation.
• Unlike ulcerative colitis, symptoms can be insidious, making diagnosis difficult
• Symptoms can be classified in to systems
• Click here to see the National Association for colitis and Crohn's disease

4.1 Gastrointestinal System

4.1.1 Symptoms

• Abdominal pain - crampy, intermittent pain is most common symptom
• Chronic diarrhoea - can vary according to which segment of bowel is affected. Ileitis leads to high volumes of watery diarrhoea, colitis leads to smaller volumes but higher frequency
• Nocturnal diarrhoea
• Bloody diarrhoea - less common than in UC
• Symptoms of intestinal strictures -
  • bloating
  • distension
  • vomiting
  • nausea
  • obstruction
• Symptoms of intestinal fistulae
  • pneumaturia
  • vaginal discharge
• Peri-anal symptoms
  • pain on defaecation
  • itching
  • incontinence

4.1.2 Signs

• Abdomen
  • Palpable mass
  • Fistulae - click here to see a picture of complex intestinal fistulae

  

• Peri-anal signs
  • fistulae - can be multiple
  • fissures
  • abscesses

   

   

   

• Mouth
  • apthous ulcers
• Hands
  • clubbing

4.2 Systemic symptoms + signs

• Fever
• Weight loss
• Growth failure in children
• Anorexia
• Cachexia

4.3 Extra-intestinal symptoms + Signs

4.3.1 Related to underlying disease activity

• Erythema nodosum
• Peripheral Arthritis
• Apthous ulcers
• Pyoderma Gangrenosum
• Episcleritis

4.3.2 Unrelated to underlying disease activity

• Uveitis
• Spondylarthropathy - Ankylosing spondylitis

4.3.3 Extra-intestinal diseases

• Gallstones
• Primary Sclerosing Cholangitis
• Nephrolithiasis
• Thromboembolism

5. Diagnosis + Investigation

• Can be difficult to reach the diagnosis of Crohn's in some patients
• History and Examination
• Bloods -
  • Hb - may demonstrate anaemia due to multiple causes - from either blood loss or B12 deficiency (due to terminal ileal disease reducing absorption) or anaemia of chronic disease
  • ESR + CRP - elevated due to inflammation. Correlate closely with disease activity.
  • Serum Albumin - hypoalbuminaemia due to malabsorption
• Stool culture - MC&S + C-Diff toxin

• AXR - may demonstrate small bowel dilatation due to stricture formation

• Colonoscopy - best test as allows visualisation of colon + terminal ileum + allows biopsies to be taken for tissue diagnosis

• Barium enema - allows diagnosis of colonic fistulae + stricture. Does not allow biopsies to be taken and may underestimate extent of disease.

• Barium follow through - May suggest the diagnosis by identification of small bowel strictures esp. terminal ileum, fistulae, ulcers, cobblestoning
• Diagnosis is made by the combination of the above tests with history and examination findings, demonstrating the typical pathological findings and manifestations of CD.

• MR Enteroclysis - small bowel mri - allows good imaging of the small bowel without the use of ionising radiation and will replace small bowel follow through as a small bowel investigation

6. Pathology (see table comparing to UC)

6.1 Macroscopic

• Can involve anywhere in the gastrointestinal tract from mouth to anus
• Three commonest sites of involvement are
  • ileocolic
  • ileal
  • colic
• Perianal disease, particularly fissures and fistulae, is common

  

• reddened mucosa + small apthous ulcers
• superficial spreading ulcers
• deep narrow ulcers
• fistulation
• extensive fissuring leaves islands of raised mucosa - cobblestoning
• Segments of bowel that are affected are known as "skip" lesions
• Areas of advanced disease, inflammation becomes fibrotic
• stricture + "hosepipe" segments

6.2 Microscopic

• Begins as a focal inflammatory infiltrate around crypts

  

• Inflammatory cells (macrophages and giant cells) invade deeper layers and organize into noncaseating granulomas (absence of granulomas does not exclude the diagnosis of Crohn's and is found in 70% of cases).

7. Management

7.1 Medical Management 

• Clinical course of CD characterized by exacerbations and remission
• Treatment is primarily medical

7.1.1 Aminosalicylates 

• 5-aminosalicylic acid derivatives (e.g. mesalazine) - less effective in Crohn's than UC

7.1.2 Corticosteroids 

• Used for in short courses and for patients with severe symptoms and in those unresponsive to aminosalicylates
• Steroids tapered slowly once remission achieved
• NOT indicated for maintenance due to complications of prolonged use

7.1.3 Antibiotics 

• Useful in co-existing infection

7.1.4 Thiopurines (azathioprine) 

• Used if steroid withdrawal is proving difficult
• Main role is steroid sparing
• Careful monitoring required to look for evidence of bone marrow suppression and hepatotoxicity.

7.1.5 Infliximab 

• Anti-TNF monoclonal antibody
• Use limited to people with severe active UC refractory or intolerant to steroids and immunosuppression, who are not appropriate for surgery.

7.2 Indications for Surgery 

• Patients requiring surgery for IBD should be under joint care of a gastroenterologist and a colorectal surgeon.
• Unlike UC, surgery for patient's with Crohn's disease is NOT curative and is aimed at bowel conservation
• Surgery should only be offered to patients with symptomatic disease including Crohn's patients with anal and peri-anal CD rather than patients with asymptomatic, radiologically identified disease or asymptomatic anal and peri-anal CD.
• Bowel resection is limited to macroscopic disease - features of which are
  • thickened hyperaemic bowel wall
  • fat encroachment
  • click here to see a picture of these features

8. Suggested further reading