Crohn's disease is an ongoing inflammatory disease of the bowel that most often causes abdominal pain and diarrhea Figure 01. Crohn's disease involves periodic pain, swelling and redness (inflammation) and loss of tissue (ulceration) of the gastrointestinal tract. Most people have involvement of the lower part of the small intestine (ileum), but any part of the digestive system can be affected, from the mouth down to the anus. Symptoms are most commonly abdominal pain and bloody diarrhea, but vary depending on the location of the inflammation.
Figure 01. Digestive System Anatomy
The disease usually starts in childhood or early adulthood, and is characterized by unpredictable flare-ups and remissions. During remissions, which may last for years, the person may feel well and be free of symptoms. Crohn's disease shares many features with ulcerative colitis, an inflammatory bowel disease that involves only the colon. Unlike ulcerative colitis, which affects only the most surface layers of the intestine (the mucosa) and spreads through the colon in a continuous fashion, Crohn's disease typically penetrates all layers of the intestine and can have a patchy distribution throughout the entire gastrointestinal tract. About 15% of patients with inflammatory bowel disease have characteristics of both conditions, and cannot be clearly diagnosed as having one or the other.
If Crohn's disease increases in severity, complications such as intestinal blockage can develop. Inflammation tends to thicken the bowel wall with swelling and fibrous scar tissue. This narrows the opening of the intestinal tube, and may eventually cause a blockage, the most common complication of Crohn's disease.
Another complication is the formation of a fistula, an abnormal passageway between two organs that do not normally connect with one another. Fistulas are formed when ulcer tracts burrow through the bowel wall and into adjacent organs, such as the bladder, the vagina, another area of bowel, or out through the skin. The introduction of intestinal contents into normally sterile areas of the body can lead to pockets of infection (abscesses). The areas around the anus and rectum are often involved in fistula formation.
Crohn's disease can be a serious disease requiring hospitalization and multiple surgeries. Crohn's disease usually starts in late childhood or early adulthood, and can seriously disrupt a person's education, career goals, and social life. Although it is not considered to be a fatal disease, it can cause anemia, malnutrition, and weakness during severe or prolonged attacks, and may require hospitalization and multiple surgeries to correct complications. Fortunately, effective medicines and surgery can help most people keep the disease in check most of the time.
Some patients with Crohn's disease also have inflammation in other parts of their body. Inflammation may also develop in the joints, skin, or eyes. Kidney stones, gallstones, and other diseases of the liver and bile system (including the liver, the gallbladder and the tract that carries bile), also tend to occur more often.
The reason some people develop Crohn's disease is unknown, though it may result from an abnormal immune response, perhaps to a virus or bacteria. Crohn's disease has been blamed on genetic factors, bacteria, viruses, stress, and dietary components, but no theory offers a clear-cut explanation. It tends to run in families, and is more common in certain ethnic groups, indicating that a genetic component and/or an infectious agent is likely.
For whatever reason, the body mounts an inflammatory response in the digestive tract (or “intestinal tract”) as if a foreign invader such as a virus, an allergen, or bacteria, were present. It's possible that the abnormal response may continue even after the provoking agent is no longer present.
People with Crohn's disease may be considerably emotionally distressed, leading some to suspect that psychological factors are the primary cause of the condition. There is no evidence, however, to support this. Instead, most experts believe that emotional disruption is an understandable and common response to a problem like Crohn's disease, a chronic condition that frequently recurs beyond one's control.
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