Crohn’s Disease

Question 1

Crohn’s Disease

Answer 1

• Crohn’s disease is a chronic relapsing inflammatory disorder of any part of the gastrointestinal tract (though nearly always small or large bowel) which predominantly affects younger people.
• About 60% of patients are under 25 years at the time of initial diagnosis, and on average, symptoms will have been present intermittently for 5 years
• The small bowel alone is affected in 50% of patients, the large bowel alone in 20% and both together in 30%. The terminal ileum is affected most commonly; in up to half of all cases, the disease is confined to the terminal ileum
• In contrast to ulcerative colitis, the inflammation involves the entire thickness of the bowel wall (transmural inflammation). Because of this, affected bowel may partially obstruct, fistulate or perforate, whereas this rarely occurs in ulcerative colitis

Question 2

Pathophysiology and clinical consequences of crohn’s disease

Answer 2

• The essential pathological feature is chronic inflammation of bowel, with inflammation extending diffusely through the entire bowel wall
• The epithelium remains largely intact but is criss-crossed by deep fissured ulcers. These large serpiginous ulcers and the intervening areas of dome-shaped mucosa and submucosa give a typical ‘cobblestone’ surface appearance

Question 3

Effects of transmural inflammation

Answer 3

• If inflamed bowel impinges on parietal peritoneum, pain becomes localised and more severe and signs of local peritonitis develop
• Crohn’s disease of the terminal ileum may mimic acute appendicitis
• At appendicectomy, the terminal ileum is visibly inflamed and the bowel wall abnormally thick to palpation

Serosal inflammation causes adhesions to adjacent abdominal structures. Complications may occur if become matted by the inflammatory process:

• Adhesions
• Perforation
• Fistulae

Question 4

Perianal inflammation

Answer 4

• Perianal inflammation occurs in 15% of patients with Crohn’s disease. Symptoms include recurrent perianal abscesses, characteristic blueish, boggy ‘piles’ (see Fig. 28.7) and anterolateral anal fissures
• Fistulae are sometimes so numerous as to cause a ‘pepper-pot’ or ‘watering-can’ perineum

Question 5

Symptoms and signs in crohn’s disease

Answer 5

• Symptoms of Crohn’s disease can be similar to those of ulcerative colitis, particularly when large bowel is involved
• Diarrhoea is usually less distressing and less likely to contain blood.
• Other characteristic symptoms include cramp-like abdominal pain, weight loss and general malaise.
• As an aide memoire, think of pain, weight loss and diarrhoea as symptomatic of Crohn’s.

Question 6

Physical examination

Answer 6

• generalised wasting and anaemia and sometimes other features like arthropathy
• On abdominal examination, there may be areas of tenderness,
• an inflammatory mass in the right iliac fossa where omentum wraps around inflamed terminal ileum or the scars of previous surgery
• Diseased rectal mucosa, with its typical firm surface nodularity, may be felt on digital examination
• typical ‘cobblestone’ appearance with fissured ulceration may be seen. Biopsies may be positive even when the mucosa is apparently normal.

Question 7

Management of Crohn’s disease (1)

Answer 7

Aim of medical therapy in active Crohn’s disease is to bring about and maintain remission:

• 5-ASA compounds, as used in ulcerative colitis. These act locally, making it a challenge to deliver oral medication to inflamed small bowel without gastric inactivation
• Sulfasalazine (a combination of 5-ASA and a carrier, sulfapyridine) is useful in ulcerative colitis and large bowel Crohn’s disease because the active ingredient is released by colonic bacteria
• Mesalazine is useful for more proximal Crohn’s disease as the active compound is released earlier
• Rectal Crohn’s treated with 5-ASA suppositories or enemas, as in ulcerative colitis. 5-ASA compounds can be used as maintenance therapy in Crohn’s
• Corticosteroids can act as systemic agents (e.g. prednisolone) or locally. Budesonide is a new oral steroid which is mostly released in the terminal ileum then rapidly inactivated by the liver after absorption, minimising systemic effects

Question 8

Management of Crohn’s disease (2)

Immunomodulators

Answer 8

• Azathioprine and 6-mercaptopurine are immunosuppressants, sometimes used in more severe Crohn’s disease
• Methotrexate acts both as an anti-inflammatory agent and an immunomodulator but has potentially serious side-effects upon liver and bone marrow
• Infliximab is a chimeric monoclonal antibody to TNFα, an inflammatory mediator. It is given by intravenous infusion for acute disease and is usually effective within 2 weeks

Question 9

The role of surgery in Crohn’s disease

Answer 9

• Surgery not considered curative in Crohn’s disease, unlike ulcerative colitis.
• This is because operating on one section of bowel does not affect later recurrences elsewhere.
• Up to 70% of patients with Crohn’s disease will eventually need surgery, of whom half will need further surgery within 5 years.

Question 10

The role of surgery in Crohn’s disease

Indications

Answer 10

• Acute complications, e.g. abscess, perforation
• Persistent local ileal disease
• Intolerable long-term obstructive and other symptoms, e.g. abdominal pain, perianal disease, general ill-health
• Entero-cutaneous fistulae and symptomatic internal fistulae