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What is Crohn’s Disease?

Reviewed by: HU Medical Review Board | Last Reviewed: January 2016.

Crohn’s disease is a long-term (chronic) inflammatory disease of the digestive tract. It can also cause symptoms and complications outside the digestive tract. The most recent estimate shows that about 780,000 people in the United States have Crohn’s disease.1

A person with Crohn’s disease has inflammation in parts of the digestive tract (Figure).2 Any part of the digestive tract can be affected. However, inflammation is most common at the end of the small intestine, which is called the ileum, and the first part of the large intestine.2

Figure. Digestive tract

Parts of the digestive tract from the esophogus to the anus that can be affected by Crohn's disease.

People with Crohn’s disease can have a wide range of symptoms. Typical symptoms of Crohn’s disease are diarrhea, abdominal pain, weight loss, and fever.3 You might notice bleeding from your anus, either in your stool, in the toilet, or on the toilet paper. You may also have symptoms outside of your digestive system, for example, in your joints, skin, and eyes.3

Long-term inflammation can cause scarring in your intestines.2 As scar tissue builds up, it becomes harder for food and waste to pass through the digestive tract. This is called a stricture. Fistulas are another long-term complication of Crohn’s disease. A fistula is a tunnel that forms between an organ and another structure because of inflammation or injury. People with Crohn’s disease can develop fistulas between the different loops of the intestines. Fistulas also develop between the intestines and other structures, such as the bladder or skin. An abscess is a collection of pus that sometimes forms near or around a fistula.

What are the different types of inflammatory bowel disease?

Crohn’s disease belongs to a group of disorders called “inflammatory bowel diseases.” Another common inflammatory bowel disease is ulcerative colitis. These 2 inflammatory bowel diseases have similar symptoms. However, they usually affect different parts of the digestive tract. Whereas Crohn’s disease typically affects the small intestine, ulcerative colitis affects the large intestine and rectum.2

What causes Crohn’s disease?

The cause of Crohn's disease is currently unknown. Researchers believe that it may be a result of multiple factors that interact with each other, including:4

  • Genes
  • Microorganisms (eg, viruses, yeasts, fungi, or bacteria)
  • Environmental factors

The current theory is that Crohn’s disease develops when your immune system overreacts to harmless microorganisms in your digestive tract.2,4 Researchers think that some people have genes that make them more likely to develop Crohn’s disease.4 This is called susceptibility. Environmental factors may be necessary to trigger the overreaction. However, it is not known which environmental factors trigger Crohn’s disease. This is an area of ongoing research.

How is Crohn’s disease diagnosed?

Your health care provider will ask questions about your symptoms.5 Tell your provider when the symptoms started and how frequently you have them. During the physical exam, your provider will feel your abdomen and examine your anus and rectum. Samples of your blood and stool will be tested.5

Endoscopy is a procedure done to confirm that you have Crohn’s disease.3 Your doctor performs this procedure using a long, thin tube with a very small camera and light. The camera lets your doctor see inside your digestive tract. Your doctor will look for signs of Crohn’s disease.3 When endoscopy is used to examine the rectum, colon, and ileum, it is called a colonoscopy. Endoscopy also can be used to look at upper parts of the digestive tract, including the esophagus, stomach, and beginning of the small intestine.5

Your provider may recommend other tests for complications of Crohn’s disease. Commonly used tests include ultrasound, computed tomography (CT) scan, or magnetic resonance imaging (MRI).3

Can Crohn’s disease be cured?

Currently, there is no cure for Crohn’s disease. People with Crohn’s disease usually have periods of active disease followed by periods of recovery (remission). Studies have shown that:3

  • If you are in remission for 1 year, the chance of remaining in remission the next year is 80%.
  • If you have had active disease in the past year, the chance of active disease in the next year is 70%.
  • If you have had active disease in the past year, the chance of remission in the next 3 years is 50%.

The goals of treating Crohn’s disease are to reduce your symptoms, improve your quality of life, reduce complications, and minimize medication side effects.

How is Crohn’s disease treated?

A variety of medications may be used to treat Crohn’s disease. These include:2

Surgery may become necessary. In one large study, half of all patients needed surgery within 10 years of being diagnosed with Crohn’s disease.6 The most common surgeries for Crohn’s disease are procedures to remove part of the intestine, open scarred areas that have gotten too narrow, or drain areas where pus has collected.5

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