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Types of Inflammatory Bowel Disease

The two main types of inflammatory bowel disease are Crohn’s disease and ulcerative colitis. There are subtypes of each of these diseases, based on what part of the digestive tract is affected. Several other diseases also can cause inflammation of the large intestine (colon). These diseases are less common, and they often have similar symptoms. For these reasons, they can be hard to diagnose.

Types of Crohn’s disease

There are 5 types of Crohn’s disease, based on which parts of the digestive tract are affected. The location of inflammation affects what symptoms you have and what type of treatment is needed.2 The Table describes the 5 types.

Table. Types of Crohn’s Disease

Type of Crohn’s Disease Affected Area
Ileocolitis/Ileoceceal Crohn’s disease Last part of the small intestine (ileum) and first part of colon.
Ileitis Last part of the small intestine (ileum)
Gastroduodenal Crohn’s disease Stomach and first part of the small intestine (duodenum)
Jejunoileitis Middle and end of small intestine (jejunum and ileum)
Crohn’s (granulomatous) colitis Some or all of the large intestine (colon)

About 6 to 15 new cases of Crohn’s disease are diagnosed per 100,000 people each year, and it is estimated that there are between 50 and 200 people living with Crohn’s disease per 100,000 people.3 Ileocolitis is the most common form. It affects about 40% of people with Crohn’s disease.4

Types of ulcerative colitis

Ulcerative colitis affects some or all of the large intestine.5 Inflammation of the rectum is called ulcerative proctitis. If the inflammation affects the entire large intestine, it is called pancolitis. About 8 to 14 cases of ulcerative colitis are diagnosed per 100,000 people each year, and it is estimated that there are 120 to 200 people living with ulcerative colitis per 100,000 people.3

Although Crohn’s disease and ulcerative cause similar symptoms, they affect the digestive tract in different ways. The inflammation caused by ulcerative colitis is limited to the large intestine. In Crohn’s disease, any part of the digestive tract could be affected.6 The pattern of inflammation differs. Crohn’s disease causes patchy areas of inflammation in different sections of the digestive tract. Ulcerative colitis causes continuous inflammation in one area. The inflammation caused by Crohn’s disease goes deeper into the intestinal wall.

What is indeterminate colitis?

Sometimes, it is not possible for a health care provider to tell whether a person has Crohn’s disease or ulcerative colitis. In this case, the term “indeterminate colitis” is used.7 This term is somewhat vague, and its use is controversial. Some people with indeterminate colitis are eventually diagnosed with a specific form of inflammatory bowel disease.7

What is microscopic colitis?

Microscopic colitis causes inflammation in the large intestine. The signs of this kind of inflammation can only be seen under a microscope.8 The 2 forms of microscopic colitis are collagenous colitis and lymphocytic colitis. About 7.1 cases of collagenous colitis and 12.6 cases of lymphocytic colitis are diagnosed per 100,000 person-years, and an estimated 103 per 100,000 people live with microscopic colitis.9 Microscopic colitis is most common in older adults. Microscopic colitis often overlaps with other autoimmune diseases, such as celiac disease.10

What is diversion colitis?

Diversion colitis is an inflammation in the part of the large intestine that is left after surgery to redirect waste (feces) out of the body. This procedure is called “fecal diversion.” It is sometimes needed to treat diseases of the large intestine.11 Normally, waste travels through the large intestine to the rectum. The waste is then eliminated through the anus. However, if there are problems with the intestine, waste can be eliminated through an ostomy, or surgical opening in the skin.

Diversion colitis develops in the part of the intestine that is no longer in use. It may develop because the bacteria in that part of the intestine live on the undigested starches and fiber in normal waste, which they are no longer getting. Most people who have fecal diversion surgery develop diversion colitis, but less than half of people have symptoms.1

Why is Crohn’s disease mistaken for Behçet’s disease?

Behçet’s disease is a rare autoimmune disease that causes inflammation of the blood vessels. The most common symptoms of Behçet’s disease are mouth ulcers, genital ulcers, and eye inflammation.1 When the digestive tract is affected, ulcers typically appear at the end of the small intestine (ileum) and start of the large intestine (cecum). For this reason, Behçet’s disease may be confused with Crohn’s disease.1 There are about 0.12 to 0.33 cases of Behçet’s disease per 100,000 people in the United States.

Written by: Sarah O'Brien and Emily Downward | Last Reviewed: December 2017.
  1. Nielsen OH, Vainer B, Rask-Madsen J. Non-IBD and noninfectious colitis. Nat Clin Pract Gastroenterol Hepatol. 2008;5:28-39.
  2. 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.
  3. Cosnes J, Gower-Rousseau C, Seksik P, Cortot A. Epidemiology and natural history of inflammatory bowel diseases. Gastroenterol. 2011 May;140(6):1785-1794.e4. doi:
  4. Freeman HJ. Application of the Montreal classification for Crohn's disease to a single clinician database of 1015 patients. Can J Gastroenterol. 2007;21:363-366.
  5. Adams SM, Bornemann PH. Ulcerative colitis. Am Fam Physician. 2013;87:699-705.
  6. The facts about inflammatory bowel disease, Crohn’s and Colitis Foundation of America. Available at Accessed 12/28/17.
  7. Tremaine WJ. Review article: Indeterminate colitis--definition, diagnosis and management. Aliment Pharmacol Ther. 2007;25:13-17.
  8. National Institute of Diabetes and Digestive and Kidney Disease. Microscopic colitis: Collagenous colitis and lymphocytic colitis. Accessed 6/12/15 at:
  9. Storr MA. Microscopic colitis: epidemiology, pathophysiology, diagnosis and current management – an update 2013. ISRN Gastroenterol. 2013; Article ID 352718, 12 pages, 2013. doi:10.1155/2013/352718.
  10. O'Toole A, Coss A, Holleran G, et al. Microscopic colitis: Clinical characteristics, treatment and outcomes in an Irish population. Int J Colorectal Dis. 2014;29:799-803.
  11. Cleveland Clinic. Treatments and procedures: Colostomy. Accessed 6/11/15 at: