Crohn’s diseasemay affect any part of the gastrointestinal tract from the mouth to the anus. It is most common in the terminal ileum and ascending colon. Crohn’s disease is more frequent in the Western world, particularly amongst Caucasians, where the prevalence is approximately 50–100 per 100 000. Its peak onset is between 20 and 40 years of age and both sexes are equally affected.
There is a high rate of concordance in monozygotic twins, which suggests both a genetic and environmental cause. However, the exact etiology is unknown. There is a 3–4-fold increase in risk with smoking and Crohn’s patients generally eat a diet higher in refined sugars and lower in fiber than those without Crohn’s. Macroscopically, the bowel appears bright red and swollen. Later, small, discrete aphthoid ulcers with a haemorrhagic rim form, so named because they look similar to aphthous ulcers in the mouth.
These progress to deeper longitudinal ulcers, which may develop into deep fissures involving the full thickness of the wall of the gastrointestinal tract. Because of this, the mucosa is often described as cobble-stoned. Aggregations of inflammatory cells and lymphocytes infiltrate the bowel wall. Mesenteric lymph nodes may be enlarged due to reactive hyperplasia. Granulomas may be present in the lymph nodes. Damage to the gastrointestinal tract in Crohn’s disease is often patchy (skip lesions) with normal areas of tissue found in between the patches.
Symptoms include diarrhea, with or without malabsorption, abdominal cramps, fever, malaise and weight loss. Clinical signs include:
- Abdominal tenderness
- Perianal lesions
- Aphthous ulcers in the mouth
- Weight loss
Diagnosis involves colonoscopy with biopsy and contrast radiography.
Complications depend on the site and extent of the lesions. Malabsorption may occur where large areas of small intestine are affected (short bowel syndrome, following surgical resection). Fistulae may form because of deep fissuring. These may be internal (between loops of gut or from the gut to the bladder), perianal, or, following surgery, open onto the skin. Crohn’s disease may also cause stricture formation, which may lead to obstruction. Acutely, perforation or hemorrhage may occur.
All Crohn’s disease patients require symptomatic relief and, for some, this is all the treatment they ever need. Diarrhoea is treated with anti-diarrhoeal drugs, such as loperamide and codeine phosphate. Depending on disease activity, further treatments are often required. To treat an acute flare up, corticosteroids are the main treatments used to induce remission. In secondary care, immunosuppressive treatments such as ciclosporin or azathioprine are often required. Sulfasalazine (an aminosalicylate) is also used to prevent relapses. Cytokine-modulating drugs such as infliximab induce remission in 70–80% of patients unresponsive to corticosteroids. Antibiotics, such as metronidazole are useful in severe perianal disease.
However, 80% of patients will require surgery at some point in their life because of:
- Failure to thrive in children
- Complications, e.g. perforation, obstruction, stricture or fistula formation
- Failure or side effects of drug therapy