Crohn's disease

Crohn's disease is an inflammatory bowel disease that affects the digestive tract, usually the small and large intestines. This causes an array of digestive and other symptoms. Once the condition begins, it lasts a lifetime.

The inflammation most often injures the final section of the small intestine, called the ileum, and the beginning of the large intestine. However, the disease can affect any part of the digestive tract, from the mouth to the anus. It can also affect other parts of the body, such as the eyes and joints.

Exactly what triggers the inflammation that starts Crohn's disease is still something of a medical mystery. A viral or bacterial infection may start the process by activating the immune system. Normally, the immune response fades away when the infection is over. In some people, though, the immune system stays active and creates inflammation in the intestines even after the infection goes away.

Symptoms of Crohn's disease

Once Crohn's disease begins, it can cause life-long symptoms that come and go. The most common symptoms include:

  • abdominal pain, usually at or below the navel, that is typically worse after meals
  • diarrhea that may contain blood
  • weight loss
  • weakness or fatigue
  • sores around the anus
  • drainage of pus or mucus from the anus
  • pain during bowel movements
  • painful mouth sores
  • loss of appetite
  • joint pain or soreness
  • back pain
  • eye inflammation that can cause pain or vision changes in one or both eyes
  • fever
  • red, tender bumps under the skin

In some people with Crohn's disease, symptoms suddenly get worse. This is called a flare. Following a flare, symptoms may disappear for a while. This is called remission.

As the inside lining and deeper layers of the intestine wall become inflamed, they can thicken or wear away in spots. This creates ulcers, cracks, and fissures. Inflammation can allow an abscess (a pocket of pus) to develop.

A common complication of Crohn's disease is called a fistula. A fistula is an abnormal connection between organs in the digestive tract, usually between one part of the intestine and another. Fistulas usually result from severe inflammation.

Diagnosing Crohn's disease

There is no single, definitive test for Crohn's disease. Instead, an individual's symptoms and test results fit a pattern over time that is best explained by Crohn's disease.

Some tests are often, but not always, abnormal in people with Crohn's disease:

  • blood tests can show a lot of white blood cells or other signs of inflammation, or anemia, a reduced number of red blood cells.
  • autoantibody tests can help tell the difference between inflammation caused by Crohn's disease from other inflammatory bowel diseases.
  • stool tests, also called feces or bowel movement tests, can detect blood in the stool from irritated intestines and tell if an infection is causing the symptoms.

Imaging tests that may be done include:

  • upper gastrointestinal series, an x-ray taken after an individual drinks a barium solution. This test can reveal places in the small intestine that are narrowed, and can also highlight ulcers and fistulas.
  • flexible sigmoidoscopy or colonoscopy lets a doctor look at the insides of the large intestine.
  • MR enterography uses an MR scan instead of x-rays to take pictures of the entire intestine.
  • wireless capsule endoscopy involves swallowing a pill-sized object that contains a tiny video camera that takes pictures of the small intestine and wirelessly sends them to a nearby computer.

A biopsy involves removing a small sample of tissue from the lining of the intestine and examining it in a laboratory for signs of inflammation. This can help confirm Crohn's disease and rule out other conditions.

Treating Crohn's disease

Several self-help strategies can help ease symptoms or prevent flare-ups of Crohn's disease. These include:

Modifying the diet. Not drinking carbonated beverages or eating high-fiber foods such as popcorn, vegetable skins, and nuts may improve symptoms. So might avoiding foods that cause gas, like beans, broccoli, and cauliflower. Drinking more liquids and eating smaller meals throughout the day, instead of three larger meals, helps some people with Crohn's disease.

Avoiding some anti-inflammatory drugs. Nonsteroidal anti-inflammatory drugs (NSAIDs) such as aspirin, ibuprofen, and naproxen can worsen Crohn's disease. If you need pain relief, ask your doctor about other options.

Not smoking. Smoking can make Crohn's disease flare up. It also increases the risk of needing surgery.


Medications are effective at improving the symptoms of Crohn's disease. Most of the drugs work by preventing inflammation in the intestines:

  • aminosalicylates suppress inflammation in the intestine and joints. These anti-inflammatory drugs, which are chemically related to aspirin, are taken as pills or via enemas.
  • antibiotics kill bacteria in irritated areas of the bowel and may also decrease inflammation.
  • antidiarrheal medications may be helpful when diarrhea is present without infection.

Other more powerful anti-inflammatory drugs may be helpful. But they can also suppress the immune system, increasing the risk of infection. For this reason, they are not often used on a long-term basis.

The newest drugs approved for treatment of Crohn's disease are tumor necrosis factor (TNF) inhibitors. These medications block the effect of TNF. TNF is a substance made by immune system cells that causes inflammation. TNF inhibitors have potentially very serious side effects. They are generally prescribed for moderate to severe Crohn's disease that is not responding to other therapies. Infliximab (Remicade) and adalimumab (Humira) are TNF inhibitors.

Bowel rest

When symptoms of Crohn's disease become severe, bowel rest gives the intestines a chance to heal. This means the only food is clear liquids. Sometimes bowel rest means not taking anything by mouth. In that case, nutrition is given through a vein.


Surgery to remove a section of the bowel is another possible treatment. In general, surgery is recommended only if a person has:

  • a bowel obstruction
  • a non-healing fistula
  • severe side effects from medications
  • symptoms that cannot be controlled with medications

Checking for colorectal cancer

Crohn's disease increases the risk of developing colon cancer, so it's important to be checked for this type of cancer with a colonoscopy every one to two years.


As a service to our readers, Harvard Health Publishing provides access to our library of archived content. Please note the date of last review or update on all articles.

No content on this site, regardless of date, should ever be used as a substitute for direct medical advice from your doctor or other qualified clinician.

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