Inflammatory bowel disease (IBD) is the chronic inflammation and irritation of tissue in the gastrointestinal tract. It can occur anywhere from the mouth to the anus, although it most often affects the intestines. When inflamed, the intestinal lining can become red, swollen, develop ulcers and bleed.  

Patients with IBD may alternate between periods where symptoms are active and times when symptoms disappear (remission). Once it appears, IBD is a lifelong disease.

In severe cases, IBD can lead to other conditions, including dehydration (from diarrhea), anemia (from blood loss), ulcers, blockage or stricture of the intestinal passage and fistulae that can also lead to the formation of abscesses outside the intestine. Toxic megacolon (when the large intestine widens and loses muscle tone) can also occur. IBD may also increase a patient’s risk of developing colon cancer. In children the condition can cause retarded growth and delays in the onset of puberty.

The exact cause in unknown, but IBD appears to occur when intestinal cells, triggered to fight harmful substances in the digestive tract, continue to fight healthy intestinal lining. Protective cells that normally exist in the intestinal walls are activated to attack bacteria and viruses when they pass through the intestines. In patients with IBD, this fighting continues, even after the harmful substances have gone. This leads to the chronic inflammation and irritation of the intestines.

After food enters the mouth, it travels through the esophagus, stomach, small intestine (where most digestion occurs) and finally the large intestine, before waste is expelled through the anus. Any area along this route (called the alimentary canal) is subject to inflammation and irritation as a result of IBD.

In the small intestine (made up of the duodenum, jejunum and ileum), IBD most commonly affects the lowest area, the ileum. IBD can occur in all sections of the large intestine, including the cecum and rectum. 

More than 1 million Americans have been diagnosed with IBD, according to the American College of Gastroenterology. There are 10 new cases for every 100,000 people each year.