Inflammatory Bowel Disease (Overview)


What is inflammatory bowel disease?

Inflammatory bowel disease (IBD) is a group of disorders that cause irritation and swelling of the digestive tract.

There are two main diseases that make up IBD: Crohn’s disease and ulcerative colitis. Both diseases cause swelling and sores in the lining of the digestive tract and symptoms such as abdominal pain and diarrhea.

Approximately 1.5 million people in the United States have either Crohn’s disease or ulcerative colitis.

What is Crohn’s disease?

Crohn's disease is a chronic (long-term) illness in which the intestine (bowel) becomes inflamed and ulcerated (marked with sores). Crohn's disease usually affects the lower part of the small intestine (ileum), although it can occur in any part of the large or small intestine, stomach, esophagus, or even the mouth. It can occur at any age, but it is most common between the ages of 15 and 30.

Crohn's disease can upset the normal working of the bowel in a number of ways. The tissue may:

  • Swell, thicken, or form scar tissue, leading to blockage of the passageway inside the bowel;
  • Develop ulcers that can go into the deep layers of the bowel wall;
  • Lose its ability to absorb nutrients from digested foods (malabsorption);
  • Develop abnormal passageways (fistulas) from one part of the bowel to another part of the bowel, or from the bowel to nearby tissues such as the bladder or vagina, and even the skin.

What is ulcerative colitis?

Ulcerative colitis is a chronic inflammatory disease that affects the lining of the large intestine (colon) and rectum. People with this condition have tiny ulcers and small abscesses (boils) in their colon and rectum that flare up every so often and cause bloody stools and diarrhea. The inflammation usually begins in the rectum and then spreads to other segments of the colon. The disease can go away for weeks to years at a time.

The main difference between Crohn’s disease and ulcerative colitis is that Crohn’s can develop anywhere in the digestive tract (from the mouth to the rectum), and penetrates into the deep layers of the lining of the digestive tract. Ulcerative colitis usually only affects the lining of the colon.

Symptoms and Causes

What is the cause of inflammatory bowel disease?

IBD is probably caused by a problem with the person’s immune system. In cases of IBD, the immune system mistakenly perceives food or other substances in the digestive tract as “foreign,” and floods the tract with white blood cells (which usually fight infections). This overflow of white blood cells causes the symptoms of IBD. The mistake by the immune system may be caused by a virus, bacteria, or allergy. IBD is often a genetic condition (runs in families).

What are the symptoms of inflammatory bowel disease?

In patients who have IBD, common symptoms may include:

Both conditions can also affect the bones, skin, and eyes.

Diagnosis and Tests

How is inflammatory bowel disease diagnosed?

Crohn’s disease and ulcerative colitis have very similar symptoms, so it can be difficult to tell which one the patient is suffering from.

Tests to diagnose IBD include the following:

  • CT Enterography: A test that allows the doctor to perform an X-ray examination of the entire abdomen. Findings of active disease include thickened bowel wall, inflamed bowel, narrowed areas, and fistulas.
  • Flexible sigmoidoscopy: A test that provides a view of the lowest two feet of the colon. The doctor inserts a slender, flexible, lighted tube through the rectum and examines this section of the colon, looking for inflammation, ulcers, or other problems.
  • Colonoscopy: The doctor inserts a thin, flexible, lighted tube that is long enough to view the entire colon with the attached camera. The doctor also can take tissue samples from inside the colon that can be tested in the laboratory for clusters of inflamed cells called granulomas. These clusters are present in Crohn’s disease but not in ulcerative colitis, so this is a very useful test for telling the difference between the two diseases.

Management and Treatment

Does diet play a role in inflammatory bowel disease?

People who have IBD and are managing it with medication can eat a “normal” diet. Patients who have chronic diarrhea usually switch to a low-roughage diet. Patients who are lactose-intolerant will avoid milk in order to prevent symptoms.

How is inflammatory bowel disease treated?

There is no cure for IBD. In the early stages of both Crohn’s disease and ulcerative colitis, medication is the recommended treatment. The goal of medical treatment is to control the inflammation and allow the intestines to heal. Once diarrhea and abdominal pain are under control, medical treatment can reduce the number of flare-ups and keep the disease in remission. The most commonly prescribed drugs for IBD are:

  • Corticosteroids such as prednisone and methylprednisolone. These powerful drugs reduce inflammation in the intestines and can help treat fistulas.
  • Aminosalicylates such as sulfasalazine and mesalamine. These are anti-inflammatory drugs.
  • Immunosuppressive drugs such as 6-mercaptopurine and azathioprine. These drugs can help reduce the dose of corticosteroids the patient has to take.
  • Metronidazole, an antibiotic that also affects the immune system. This drug is helpful for patients who have fissures or abscesses.
  • Biologics, for patients who have moderate to severe IBD. Biologics include infliximab, adalimumab, certolizumab, golimumab, natalizumab, and vedolizumab.

Up to three-quarters of Crohn’s disease patients and one-quarter of ulcerative colitis patients will need surgery. The type of operation the patient needs depends on the disease.

In the case of ulcerative colitis, surgery may mean removing the entire colon, especially when medications are not effective or if the patient has severe complications of the disease. Surgery to remove the entire large intestine (colectomy), or both the colon and rectum (proctocolectomy) removes the threat of colon cancer.

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Cleveland Clinic is a non-profit academic medical center. Advertising on our site helps support our mission. We do not endorse non-Cleveland Clinic products or services. Policy

Cleveland Clinic is a non-profit academic medical center. Advertising on our site helps support our mission. We do not endorse non-Cleveland Clinic products or services. Policy