Pathophysiology of inflammatory bowel disease: An overview

Inflammatory bowel disease, Crohn's disease, and ulcerative colitis are considered idiopathic diseases affecting the gastrointestinal tract. These two diseases are often considered together because of multiple similarities, including gastrointestinal inflammation, waxing and waning severity and symptoms, and unknown etiology. However, they have separate symptoms and microscopic characteristics as well as patterns within the gastrointestinal tract (Table 1). The incidence of inflammatory bowel disease varies according to geographic location. Higher rates are typically found in the more developed countries of Scandinavia, northern Europe, and North America, with lower rates in Asia, Africa, and South America. However the incidence is increasing in the less-developed countries as they become more industrialized, implicating environment, diet, and cultural practices as potential risk factors. Other epidemiologic studies have shown that inflammatory bowel disease typically affects young people; however, there is a bimodal incidence with a large peak in the second or third decade of life followed by a smaller peak later in life. The bimodal distribution is seen more consistently with ulcerative colitis than with Crohn's disease [1].