Inflammatory Bowel Disease (IBD)

Inflammatory bowel disease (IBD) is an umbrella term that refers to both ulcerative colitis and Crohn’s disease. However, about 10% of patients cannot reliably be put into either category based on their evaluation, and are characterized as having indeterminate colitis.

Ulcerative colitis is a disease of the colon in which inflammation of the mucosa (lining) of the large intestine occurs.

Crohn’s disease can cause inflammation of the lining and wall (transmural) of the large and/or small intestine. Additionally, a small percentage of patients can have Crohn’s of the upper gastrointestinal system (mouth, esophagus, stomach). 

The most common symptoms of ulcerative colitis, which occurs in the lining of the colon (large intestine) and/or rectum only, are diarrhea, rectal bleeding—often with mucous—and abdominal pain.

Patients who suffer from Crohn’s disease, an inflammatory and ulcerative process that often extends to the deep layers of the intestinal wall, may experience pain in the abdomen, often in the lower right side, diarrhea, weight loss and occasionally bleeding. Some Crohn’s patients present with obstructive symptoms, specifically sudden onset of uncontrollable nausea, vomiting, and abdominal pain.

Both Crohn’s disease and ulcerative colitis are chronic illnesses with periods of remission (when your disease is inactive and you feel well) and relapse (when your disease is active and you feel ill).  Many patients with IBD will also have irritable bowel syndrome (IBS), which may mimic certain symptoms of IBD, but in IBS there is no bleeding or other evidence of tissue inflammation.  Occasionally, patients may have a superimposed bacterial infection which may mimic IBD symptoms, with bleeding, diarrhea, and pain. Your doctor will work with you to discern between these, which have very different treatment plans.

There are many different types of treatment plans that your doctor can prescribe to control the symptoms of IBD, and each of these has specific therapeutic actions and side effects.


IBD occurs most frequently in people in their late teens and twenties. However, there have been cases in children as young as two years old and in older adults in their seventies and eighties.

The causes of IBD are not known, but there are several theories. One theory is based on genetics, suggesting that IBD does run in families. About 15 percent to 30 percent of patients with IBD have a relative with the disease. There is research underway to find out if a specific gene or a group of genes makes a person more susceptible to getting the disease. Men and women are affected equally by IBD.

Another theory suggests dysregulation of the body’s intestinal immune system (body’s natural defense system against disease) is a major cause of IBD. What is still unknown is why this occurs. There is a large amount of research being done in this area, including studies to find out how an infectious agent, such as a bacterium, can trigger the dysregulation of the intestinal immune system in certain people. 

Stress or certain foods do not cause IBD. As with other illnesses, stress may aggravate symptoms of IBD or IBS and require a specific treatment program.


Learn more about Gastroenterology at The Oregon Clinic