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BCM - Baylor College of Medicine

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Inflammatory Bowel Disease Center

Crohn's Disease

Crohn's disease is a chronic inflammatory disease of the digestive system. Both Crohn's disease and ulcerative colitis are referred to as inflammatory bowel disease (IBD), not to be mistaken for irritable bowel syndrome (IBS), a different disease of the digestive system. Crohn's disease may affect any part of the digestive system from the mouth all the way to the anus. However, the most common locations affected by Crohn's disease are the end of the small intestine (referred to as the terminal ileum), and the colon. There are several ways to diagnose Crohn's disease, usually requiring at least a colonoscopy. See Diagnostic Testing for Inflammatory Bowel Disease for more details.

For more information see: Inflammatory Bowel Disease.

What causes Crohn's disease?

Unfortunately the cause of Crohn's disease is unknown, although both genetic and the environmental causes have been proposed.

Most people with Crohn's disease do not have anyone else in the family with Crohn's disease. However up to 20 percent of patients with Crohn's disease have at least one relative with either Crohn's disease or ulcerative colitis. Several genetic mutations have been identified to be associated with Crohn's disease. However these genes are also found in people who do not have Crohn's disease and many patients with Crohn's disease do not have these genetic mutations. Testing for one of these genes is available, but only your doctor can tell you if it is appropriate to obtain this test.

The increase in Crohn's disease in certain populations around the world has led some researchers to believe there may be environmental causes or triggers for Crohn's disease. Infections and diet are among other potential environmental triggers for Crohn's, however there is not enough information in this field to make any firm conclusions. There is still much to learn in these areas and research is ongoing to determine the cause of Crohn's disease. 

What are the symptoms of Crohn's disease?

Although the cause of Crohn's disease is unknown, the effects of Crohn's disease on the body are becoming better understood. In Crohn's disease, the body's own immune system is overactive and results in inflammation in the digestive system. This may be a response to the bacteria normally found in the human digestive tract, or "gut flora." The persistent inflammation results in the damage and ultimately the symptoms of Crohn's disease. Most medications for Crohn's disease work by decreasing or "turning down" the immune system to reduce the inflammation and damage in the digestive tract. More recent medications target very specific molecules to decrease inflammation. There are currently three medications that target a molecule called tumor necrosis factor (TNF) to treat Crohn's disease. For more information on the medications for Crohn's disease, see Medications for Inflammatory Bowel Disease.

The most common symptoms relate to inflammation in the small intestine and the colon, which are abdominal pain and diarrhea. Some patients may also have blood in their stool and weight loss. These symptoms may also be seen in other medical conditions and are considered non-specific to Crohn's disease. Most patients can have at least partial if not complete relief of these symptoms with medications, which we call "remission." However patients may have symptoms return periodically, or "flare" over time even if they are taking their medications.

Smoking may worsen symptoms of Crohn's disease, decrease responsiveness to medications, and increase the risk of complications of Crohn's disease. All patients with Crohn's disease should discuss with their doctor if they continue smoking and should seek assistance in quitting.

What are the complications of Crohn's disease?

Strictures. Inflammation in the intestines may develop a narrow area, or stricture. This may result in a blockage of intestinal contents, also called an obstruction. This may become an emergency and require surgery. Patients may shows signs of abdominal pain, nausea, and vomiting. If the stricture is caused by inflammation, it may improve with medications. However, if the stricture has formed scar tissue, it may require surgery. In certain circumstances, the stricture may be stretched during an endoscopy, which is called dilation, in order to avoid or postpone surgery. Dilation may be limited by the location and length of the stricture.

Fistulas. Fistulas are connections that form from the intestines to another part of the body due to the inflammation. Fistulas may form from one part of the intestine to another and cause more diarrhea. They may also connect to near-by organs such as the bladder and cause recurrent infections. In some patients, fistulas may form around the anus and result in infections. There are some medications that may help fistulas heal, but they may require surgery. 

Patients with Crohn's disease may have symptoms in parts of their body outside of the digestive system.

Joints. There are forms of arthritis and back pain that are related to Crohn's disease. Some of these conditions improve with medications for the digestive symptoms of Crohn's disease. The use of over-the-counter pain medications such as ibuprofen, naproxen, and aspirin may increase the symptoms of Crohn's disease. Patients with Crohn's disease should speak with their gastroenterologist before using these medications.

Eyes. Some patients with Crohn's disease develop inflammation in the eyes, called iritis or uveitis. Iritis may results in redness or eye pain and may fluctuate with the severity of the digestive symptoms of Crohn's disease. Uveitis may results in severe eye pain and loss of vision. Patients with Crohn's should see an eye doctor on a regular basis and report any changes in their vision to their doctor immediately.

Skin. There are two conditions related with Crohn's disease, erythema nodosum and pyoderma gangrenosum. Erythema nodosum are painful red bumps under the skin that may develop when the Crohn's disease flares, these lesions will often respond to the medication for Crohn's disease. Pyoderma gangrenosum are skin ulcers that may form either with or without a flare of Crohn's digestive symptoms.

Other complications of Crohn's disease include kidney stones, a liver condition called primary sclerosing cholangitis (PSC), and malabsorption of vitamins and nutrients. 

What is life like with Crohn's disease?

There is no cure for Crohn's disease. However, our goal is to allow our patients to live a full and productive life with Crohn's disease. Most patients will require medications for an indefinite period of time. Research has shown that patients with Crohn's disease who do not take their medication, even if they are feeling well, are more likely to have a return of their symptoms compared to patients who continue their medications. It is very important that patients discuss with their doctor if they are considering stopping their medications.

It is important for patients with Crohn's disease, even if they are feeling well, maintain regular visits with their physician. For example:

  • Patients on medications may need routine blood work to monitor for side effects.
  • Patients with Crohn's disease should keep up to date on immunizations including influenza (flu), pneumococcal (pneumonia), human papilloma virus (HPV), and hepatitis A and B.
  • Some patients with Crohn's disease, particularly those who have had been exposed to steroids (prednisone), may need to have bone mineral density tests to screen for early osteoporosis.
  • Some patients with Crohn's disease will need to have colonoscopies to screen for colon cancer.