There are five subtypes of Crohn's disease, distinguished by the gastrointestinal area in which the disease occurs. While Crohn's disease lesions can appear anywhere in the digestive tract, lesions rarely occur in the mouth, esophagus, and stomach unless there are also lesions in the lower parts of the tract (intestines).
- Gastroduodenal CD - Gastroduodenal Crohn's disease, which affects the stomach and the duodenum (the highest, or beginning, portion of the small intestine), is often misdiagnosed as ulcer disease. The correct diagnosis frequently is not made until various ulcer treatments have failed, or until Crohn's disease is identified farther down the gastrointestinal tract. Symptoms of gastroduodenal CD include loss of appetite, weight loss, nausea, pain in the upper middle of the abdomen, and vomiting.
- Jejunoileitis - Jejunoileitis is Crohn's disease of the jejunum (the longest portion of the small intestine), which is located between the duodenum and the ileum. Symptoms include mild to intense abdominal pain and cramps after meals, diarrhea, and malnutrition caused by malabsorption of nutrients. (The majority of nutrients are absorbed in the jejunum.) Fistulas (abnormal openings in the intestinal tract) may form. These can link a diseased area of the small intestine to another area of the intestine or another organ, such as the bladder. Fistulas may increase the risk of developing infections outside of the GI tract.
Ileitis- Ileitis affects the ileum (the lowest, or last, part of the small intestine). Symptoms include diarrhea and cramping or pain in the right lower quadrant and periumbilical (around the bellybutton) area, especially after meals. Malabsorption of vitamin B12 can lead to tingling in the fingers or toes (peripheral neuropathy). Folate deficiency can hinder the development of red blood cells, putting the patient at higher risk of developing anemia. Fistulas can develop, as can inflammatory masses. Ileocolitis- Ileocolitis is the most common type of Crohn's disease. It affects the ileum (the lowest part of the small intestine) and the colon (the large intestine). Often, the diseased area of the colon is continuous with the diseased ileum, and therefore involves the ileocecal valve between the ileum and the colon. In some cases, however, areas of the colon not contiguous with the ileum are involved. Symptoms of ileocolitis are essentially the same as those present in ileitis. Weight loss is also common.
- Crohn's Colitis (Granulomatous Colitis ) - Crohn's colitis affects the colon. It is distinguished from ulcerative colitis in two ways. First, there are often areas of healthy tissue between areas of diseased tissue; ulcerative colitis is always continuous. Second, while ulcerative colitis always affects the rectum and areas of the colon beyond the rectum, Crohn's colitis can spare the rectum, appearing only in the colon.