Physicians may use different terms to describe CD, depending on what part of the digestive tract is affected.
The most common form of CD is ileocolits, which affects the ileum (lower end of the small intestine) and the colon (large intestine). Symptoms of this type of CD include diarrhea, cramping pain in the lower right or middle abdomen, and substantial weight loss. In some cases the diseased areas in the ileum and the colon may be contiguous, affecting the ileocecal valve that connects the two sections.
Ileitis, also known as fistulizing or perforating CD, affects only the ileum. Diarrhea, cramping pain in the the lower right or middle abdomen, and discomfort a few hours after eating a meal are common symptoms. This type of CD can lead to nutritional deficiencies in B12, causing tingling in the fingers or toes (peripheral neuropathy), or folate, which may result in anemia. Complications can include fistulas or abscesses in the right lower quadrant.
Gastroduodenal CD affects the stomach and duodenum (first part of the small intestine). Symptoms include loss of appetite, weight loss, nausea, and vomiting. Vomiting may be a sign of obstruction in narrowed portions of the small intestine. This form of CD is sometimes misdiagnosed as an ulcer, with the CD being discovered after ulcer treatments are ineffective in relieving symptoms.
Jejunoileitis is characterized by intermittent areas of inflammation in the jejunum (middle section of the small intestine). Symptoms include crampy pain after meals, diarrhea, and abdominal pain that can vary from mild to intense. Complications of jejunoileitis include fistulas and malnutrition caused by poor absorption of nutrients.
Crohn's colitis (CC), sometimes called granulomatous colitis, affects only the colon and is sometimes confused with UC. However, there are two distinct differences between CC and UC: inflammation in UC is always contiguous, while in CC it is intermittent throughout the colon, and UC always affects the rectum while CC may not. Symptoms include diarrhea, bleeding from the rectum, and abscesses, fistulas, or ulcers around the anus. Peripheral arthritis and skin conditions are found more frequently with CC than the other types of CD.
What causes CD?Scientists are not certain what causes CD, so it is known as an idiopathic disease, or a disease with unknown cause. However, there are theories about the origins of CD.
CD is an autoimmune disease, or a disease that is triggered by the immune system. The medical community has noticed seasonal flare-ups (in the spring or autumn) in people with IBD. One theory is that this is a IgE-mediated allergic response.
IgE is a type of immunoglobulin isotype, which is a special protein that helps inactivate organisms that may cause disease. The function of IgE is to bind itself to an antigen and inactivate or remove offending foreign substance. However, IgE tends to attach itself to receptors on mast cells which triggers allergy symptoms such as a runny nose. If an antigen binds itself to one of these IgE cells, the mast cells are activated, and release histamine, heparin, cytokines, leukotrines, and other chemicals.
The presense of leukotrines attracts a new type of cell called an eosinophil. These cells fight off the allergic response, but the chemicals that they use to do so are toxic to the body as well as to the invading infection. The connection between eosinophils and IBD is that three of the four toxic compounds that are released by eosinophil cells are found in in the stool of IBD patients.
A controversial theory is that the bacteria M. paratuberculosis can also cause CD in humans. One study conducted on intestinal tissue removed during surgery from patients with CD, UC or without IBD found that 65% of the CD patient samples contained the bacteria, contrasting with only 12.5% of non-IBD patients. The researchers conclude that the bacteria may play a role in some cases of Crohn's disease.
