Introduction
The term inflammatory bowel disease (IBD) encompasses two chronic inflammatory disorders of the gastrointestinal tract, ulcerative colitis and Crohn's disease. The aim of this chapter is to review the abnormalities of platelet number, morphology and function which occur in IBD, the possible role of platelets in its pathogenesis, and the relevance which pharmacological modification of platelet function may have to its treatment.
Inflammatory bowel disease
Ulcerative colitis affects only the colon, while Crohn's may involve any part of the bowel from mouth to anus. The incidence of ulcerative colitis is about 10/100 000/year, and of Crohn's disease about half that figure: their combined prevalence approximates 200/100 000 of the population. Both diseases are commonest in the Western world, and their most frequent age of onset is 20–35 years.
Clinical features
Ulcerative colitis and Crohn's disease of the colon most commonly present with bloody diarrhea, while Crohn's disease of the small intestine tends to cause not only diarrhea but also abdominal pain, weight loss, malaise and fever. Both diseases are characterized by a waxing and waning natural history, and may be complicated, in patients with chronic extensive colitis, by the development of colorectal cancer. Ulcerative colitis and Crohn's disease may be associated with extraintestinal manifestations including iriitis, erythema nodosum, pyoderma gangrenosum, joint disease, a spectrum of hepatobiliary disorders and systemic thromboembolic events.