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.

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.

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