Disease Description

IBD Curriculum Topic 1.2
IBD Curriculum Topic 2.1
IBD Curriculum Topic 3.2

Together with ulcerative colitis, Crohn’s disease is one of the main inflammatory bowel diseases (IBD). Crohn’s disease can occur in any part of the gastro-intestinal tract. The terminal ileum / proximal colon are affected in the majority, though disease may co-exist in other locations (foregut, small intestine, colon, and perineum). 

Crohn’s disease is a lifelong disease, with a fluctuating course characterized by flares and remissions.. It often presents in late adolescence or early adulthood, although can occur at any age. Periods of active disease might result in complications such as intestinal fistulae (penetrating disease) or tissue scarring and lumen narrowing (stricturing disease); patients with no such complications have a pure inflammatory disease course (non-stricturing, non-penetrating disease). A disease classification based on disease behavior, location and age at diagnosis (the Montreal Classification, attached beneath) is available.

Extra-intestinal manifestations occur in 35% patients, and are more frequent when the colon is involved. Type 1 peripheral arthritis, erythema nodosum, oral aphthous ulcers and episcleritis are associated with disease activity; while pyoderma gangrenosum, uveitis, axial arthropathy and primary sclerosing cholangitis (PSC) are generally independent of disease activity. Metabolic bone disease (osteopenia and osteoporosis) is found in 20-50%. Adverse psychosocial issues are common and often under-recognised by health care providers.

Symptoms depend on disease location and behaviour. The most common presenting symptom is loose stool consistency, typically for at least 6 weeks. Other common presenting symptoms are:-

  • abdominal pain (in 70%)
  • weight loss (in 60%)
  • iron deficiency and associated anaemia
  • rectal mucus and bleeding (in 40% with Crohn’s colitis)
  • extra-intestinal manifestations (joint, eye, skin or hepato-biliary disease)
  • perianal fistula (occur in 10%)

Patients can present with acute symptoms and mistakenly be diagnosed with acute appendicitis, or with more indolent symptoms typical of the irritable bowel syndrome (IBS). 15% of patients have penetrating lesions (fistulas or abscesses) at diagnosis.

There is no gender bias. Crohn’s disease is more common in developed countries (there is a North-South gradient within Europe).

Fistulating perianal disease

A fistula is an abnormal connection between two body surfaces. In Crohn’s disease, fistula often arise in the perianal area. They communicate between segments of  intestine (entero-enteric fistula), other organs or the abdominal wall (entero-cutaneous fistula).

Symptoms include leakage of mucus / pus and sometimes faecal matter; and pain if an abscess is present. Sometimes there may be no symptoms.

The principles of management of fistula are:

  1. Locate the origin and anatomy of the fistula.
    • Determine which organs are affected.
  2. Exclude local abscess.
  3. Evaluate whether the originating intestinal loop is inflamed and/or stenosed.
  4. Assess patient’s nutritional state.

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