Inflammatory Bowel Disease (IBD)

Medically reviewed by: Stephanie Curreli, MD, PhD
Last Updated: Mar 1, 2019


Inflammatory bowel disease (IBD) refers to those conditions that cause chronic irritation, redness, and swelling (inflammation) of the gastrointestinal tract.

This type of inflammation is associated with a disorder in the body’s immune system. Normally, a healthy immune system protects the body from harmful foreign substances, destroys germs, and prevents infections. In IBD, the body’s immune system Small intestine highlighted among surrounding digestive anatomymalfunctions and mistakenly mounts an attack on food and the lining of the gastrointestinal tract, resulting in chronic inflammation in the intestines. This condition leads to tears, sores (ulceration), and destruction of the lining of the intestinal wall.

The two main types of IBD are Crohn’s disease and ulcerative colitis. Crohn’s disease usually affects the lower part of the small intestine (ileum), but it may involve any part of the digestive tract including the mouth, esophagus, stomach, small intestine, large intestine, and rectum. Furthermore, Crohn’s affects every layer of the bowel wall. Ulcerative colitis is distinctly different because it only affects the large intestine (colon) and only involves the inner lining of the bowel.

Inflammatory bowel disease is not the same as irritable bowel syndrome, which involves chronic abdominal symptoms without the intestines having a diseased appearance.

Causes and Risk Factors

The cause of inflammatory bowel disease is not known. There is no evidence that emotional stress or any particular food triggers the disease.

Although the actual trigger is unclear, several risk factors are identified:


IBD is a life-long disorder characterized by bouts of recurring symptoms alternating with symptom-free periods known as remissions.

Typical symptoms include:

Numerous complications associated with IBD include:

Diagnosis and Treatment

Sigmoid colon in the large intestine

Various tests are used to diagnose IBD:

The goal of treatment is to control inflammation, alleviate symptoms, and achieve long-term symptom-free periods of remission.


  1. Aminosalicylates. These anti-inflammatory medications decrease pain and swelling in the tissues. Examples include sulfasalazine, mesalamine, balsalazide, and olsalazine. These relatively mild drugs are associated with few side effects, except some patients experience nausea and abdominal discomfort.
  2. Corticosteroids. Stronger anti-inflammatory drugs called corticosteroids are indicated for moderate to severe cases of IBD. Examples include budesonide and prednisone. Patients may experience serious side effects such as blood sugar elevation, mood changes, worsening osteoporosis, and an increased risk for infections.
  3. Immunosuppressive drugs. These agents block activities in the immune system and stop the attack on the intestines. Examples include 6-mercaptopurine, azathioprine, and methotrexate. These medications also increase the risk for infections.
  4. Biological therapies. These powerful medications are man-made versions of human proteins called antibodies. Examples include infliximab (Remicade®) and adalimumab (Humira®), which effectively block the immune system and are indicated for moderate to severe IBD when other therapies fail. These drugs increase a person’s risk of developing cancer and serious infections such as tuberculosis.
  5. Antibiotics. Medications that destroy bacteria are prescribed to treat intestinal infections.
  6. Other medications. Antidiarrheal medications help relieve diarrhea. Vitamins and nutritional supplements help correct nutritional deficiencies.


Large intestine highlighted among digestive anatomy

Surgery is necessary when medications can no longer control the disease. Eventually, most patients undergo surgery to remove diseased portions of intestines. Ulcerative colitis, which is confined to the colon, is cured by surgery to remove the rectum and colon (proctocolectomy). Unfortunately, Crohn’s disease may involve any area of the digestive tract, so the disease often recurs in other areas after surgery.

Given the increased risk of developing colon cancer, patients with ulcerative colitis must have routine screening colonoscopies to look for precancerous changes, a definite indication for surgery.


The cause of IBD is unclear, but non-smokers appear to have a lower risk of developing the disease.

While there are no special diets that can prevent inflammatory bowel disease, avoidance of certain foods may improve the symptoms. Dairy products and high-fiber foods may worsen the symptoms of abdominal pain and diarrhea. Generally, patients are advised to experiment with their diets to determine which items exacerbate their condition.


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Tina Shahian, PhD

Tina is a Life Science Writer for a number of online publications, including Her expertise is in conveying complex scientific topics to diverse audiences. Tina earned her PhD in Biochemistry from the University of California, San Francisco and her BS degree in Cell Biology from U.C. Davis. In her spare time, she enjoys drawing science-related cartoons.