What is Crohn's Disease?

Crohn’s disease may occur in any part of the large intestine (also called the colon). In fact, it can happen anywhere in the entire digestive system.


However, it most commonly develops right where the small and large intestine meet. That’s at the ileum, the lower part of the small intestine. Sometimes Crohn’s disease of the ileum is referred to as ileitis. When Crohn’s affects the colon, it may be called Crohn’s colitis. If it involves both the ileum and the colon, the disease may be referred to as ileocolitis.


Crohn’s disease affects all the layers of the intestinal wall—causing inflammation and swelling as well as ulcers. In turn, this irritation may lead to bleeding. It also prevents the intestine from absorbing nutrients from food.


If you have Crohn’s disease, you may experience any or all of the following symptoms:

  • Diarrhea (sometimes bloody)
  • Stomach cramps or pain
  • Weight loss
  • Fever
  • Dehydration

All of those symptoms may leave you feeling pretty wiped out. In addition to fatigue, you also may not have much of an appetite. And the diarrhea, cramping, and pain may become worse when you eat because of the increased intestinal activity—so you really may not feel like eating.


But Crohn’s disease is not the same for everyone. Symptoms vary from person to person. Some people may have a lot of discomfort and frequent diarrhea.


Others may have only occasional diarrhea and very little pain. Sometimes the inflammation and ulcers can penetrate through the walls of the intestine, forming an abscess (a collection of pus). An abnormal connection with other parts of the intestine or other organs also may form. This is called a fistula.