Inflammation is a key feature of Crohn’s disease.1 It can affect any part of the digestive tract, from the mouth to the rectum.2 Inflammation is most often found at the end of the small intestine (ileum).3

Inflammation develops when the immune system fights something that is harmful—or that seems to be harmful.4 The body releases chemicals that cause blood vessels to widen. This brings more blood to the damaged area. The area becomes red and swollen. White blood cells travel to the affected areas to fight invading bacteria or viruses (microorganisms).

Why does inflammation develop in Crohn’s disease?

Inflammation is helpful after an injury or infection. However, the immune system sometimes overreacts to something harmless. Scientists think that the inflammation in Crohn’s disease happens when your immune system overreacts to harmless microorganisms in your digestive tract.3,5 The white blood cells gather in the intestine to fight the microorganisms. They remain in the intestine, causing lasting inflammation.3

People with Crohn’s disease may also have inflammation in other parts of the body. The joints, skin, and eyes and liver are particularly likely to be affected.1

What other conditions can cause inflammation in the digestive tract?

Crohn’s disease is one of many inflammatory bowel diseases. The other major inflammatory bowel disease is ulcerative colitis. Several other less common diseases also cause inflammation in the digestive tract. These include:

  • Collagenous colitis
  • Lymphocytic colitis
  • Diversion colitis
  • Behçet’s disease

How is inflammation in the digestive tract evaluated?

If you have symptoms of Crohn’s disease, your health care provider will do some laboratory tests. Some of these blood tests check for inflammation, including white blood cell counts, blood sedimentation rates, and C-reactive protein.1 Your provider may also test a sample of stool for markers of inflammation.

Your provider will confirm the diagnosis by looking inside your digestive tract for signs of Crohn’s disease and taking samples of tissue.1,2 The procedure to do this is called colonoscopy with biopsy. Your doctor performs this procedure using a long, thin tube with a very small camera and light. The camera lets your doctor see inside your digestive tract. Crohn’s disease causes patches of inflammation in different parts of the digestive tract. Between the patches, the tissue is normal.

Tissue samples are taken from the digestive tract. A doctor will look at the samples with a microscope for signs inflammation. About 30% to 45% of people with Crohn’s disease have granulomas.6,7 Granulomas form when inflammatory cells collect in one spot.8 Granulomas may be an early sign of Crohn’s disease.8

What medications treat inflammation related to Crohn’s disease?

The medications used to treat Crohn’s disease reduce inflammation. They work in a variety of ways.

Aminosalicylates are used to treat mild to moderate Crohn’s disease. These medications block a chemical called prostaglandin from forming.9 This reduces pain and inflammation. Aminosalicylates treat local inflammation in the digestive tract, rather than throughout the whole body. These medications come in many forms. The tablet forms have a special coating that only dissolves once the medication has reached its target in the digestive tract.10 These medications also come as an enema or suppository. These forms treat inflammation in the lower part of the large intestine. An enema involves injecting a liquid medication into the large intestine via the rectum. A suppository is a solid medication that is inserted into the rectum, where it dissolves.

Corticosteroids are used for the short-term treatment of Crohn’s disease. They reduce inflammation and suppress the immune system. Several corticosteroids reduce inflammation throughout the whole body. One corticosteroid, budesonide, mainly works in the digestive tract. This approach causes fewer side effects.10

Immunomodulators weaken the immune system. This reduces the inflammatory response.10 These medications treat moderate or severe Crohn’s disease, when other medications have not worked.1

Biologics are new medications for treating severe Crohn’s disease.10 Inflammation is a complicated process with many steps. At each step, certain things must happen in order for the process to continue. Biologic medications target specific proteins with a role in this process. By blocking 1 step, they can prevent the whole process from continuing.

What are complications of long-term inflammation?

Inflammation eventually causes scarring in your intestine.3 Scar tissue builds up over time, making it harder for food and waste to pass through the digestive tract. The narrowing of the digestive tract is called a stricture.

Large, inflamed masses can form in the abdomen.8 Theses masses are called abscesses. About 10% to 30% of people with Crohn’s disease will have an abscess.11 One cause of abscess formation is inflammation that extends deep into wall of the intestine.

Abscesses can cause abnormal connections to form between the intestine and other organs.11 These connections are called fistulas. Fistulas can develop between different loops of the intestine. They also develop between the intestine and other structures, such as the bladder or skin. Fistulas also can cause abscesses to form.

view references
  1. Lichtenstein GR, Hanauer SB, Sandborn WJ; Practice Parameters Committee of American College of Gastroenterology. Management of Crohn's disease in adults. Am J Gastroenterol. 2009;104:465-483.
  2. Wilkins T, Jarvis K, Patel J. Diagnosis and management of Crohn's disease. Am Fam Physician. 2011;84:1365-1375.
  3. National Institute of Diabetes and Digestive and Kidney Disease. What I need to know about Crohn's disease. Accessed 5/25/15 at:
  4. PubMed Health. What is an inflammation? Accessed 6/14/15 at:
  5. Carrière J, Darfeuille-Michaud A, Nguyen HT. Infectious etiopathogenesis of Crohn's disease. World J Gastroenterol. 2014;20:12102-12117.
  6. Hedrick TL, Friel CM. Colonic crohn disease. Clin Colon Rectal Surg. 2013;26:84-89.
  7. Denoya P, Canedo J, Berho M, et al. Granulomas in Crohn's disease: Does progression through the bowel layers affect presentation or predict recurrence? Colorectal Dis. 2011;13:1142-1147.
  8. Freeman HJ. Natural history and long-term clinical course of Crohn's disease. World J Gastroenterol. 2014;20:31-36.
  9. Cheifetz AS, Cullen GJ. Patient information: Sulfasalazine and the 5-aminosalicylates (Beyond the Basics). Accessed 6/14/15 at:
  10. Crohn’s and Colitis Foundation of America. Types of medications. Accessed 6/14/15 at:
  11. Richards RJ. Management of abdominal and pelvic abscess in Crohn's disease. World J Gastrointest Endosc. 2011;3:209-212.
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