Health Library

Colitis

Colitis is swelling (inflammation) of the large intestine (colon).

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Causes

Most of the time, the cause of colitis is not known.

Causes of colitis include:

• Infections caused by a virus, bacteria or parasite
• Crohn disease
• Ulcerative colitis
• Lack of blood flow to the colon (ischemic colitis)
• Past radiation to the colon (radiation colitis and strictures)
• Necrotizing enterocolitis in newborns
• Pseudomembranous colitis caused by Clostridium difficile infection (now called Clostridiodes difficile)

Symptoms

Symptoms can include:

• Abdominal pain and bloating that may be constant or come and go
• Bloody stools 
• Constant urge to have a bowel movement (tenesmus)
• Dehydration
• Diarrhea
• Fever

Exams and Tests

The health care provider will perform a physical exam. You will also be asked questions about your symptoms, such as:

• How long have you had the symptoms?
• How severe is your pain?
• How often do you have pain and how long does it last?
• How often do you have diarrhea?
• Have you traveled recently?
• Have you taken antibiotics recently?
• Is there associated rash or sores in the mouth (aphthous ulcerations)?

Your provider may recommend a flexible sigmoidoscopy or colonoscopy. During this test, a flexible tube is inserted through your rectum to examine your colon. You may have biopsies taken during this exam. Biopsies may show changes related to inflammation. This can help determine the cause of colitis.

Other studies that can identify colitis include:

• CT scan of the abdomen
• MRI of the abdomen
• Stool culture
• Stool examination for ova and parasites

Treatment

Your treatment will depend on the cause of the disease.

Outlook (Prognosis)

The outlook depends on the cause of the problem.

• Crohn disease is a chronic condition which has no cure, but can be controlled. Biologic agents are very effective in controlling symptoms of Crohn colitis.
• Ulcerative colitis can usually be controlled with medicines, including biologic agents. If not controlled, it can be cured by surgically removing the colon.
• Viral, bacterial, and parasitic colitis can be cured with appropriate medicines.
• Pseudomembranous colitis caused by Clostridioides difficile can usually be cured with appropriate antibiotics.

Possible Complications

Complications may include:

• Bleeding with bowel movements
• Perforation of the colon
• Toxic megacolon

When to Contact a Medical Professional

Contact your provider if you have symptoms such as:

• Abdominal pain that does not get better
• Blood in the stool or stools that look black
• Diarrhea or vomiting that does not go away
• Swollen abdomen

Related Information

References

Ananthakrishnan AN, Regueiro MD, Rubin DT. Management of inflammatory bowel diseases. In: Chung RT, Rubin DT, Wilcox CM, eds. Sleisenger and Fordtran's Gastrointestinal and Liver Disease. 12th ed. Philadelphia, PA: Elsevier; 2026:chap 118.

Lichtenstein GR. Inflammatory bowel disease. In: Goldman L, Cooney KA, eds. Goldman-Cecil Medicine. 27th ed. Philadelphia, PA: Elsevier; 2024:chap 127.

Pardi DS, Tome J. Other diseases of the colon. In: Chung RT, Rubin DT, Wilcox CM, eds. Sleisenger and Fordtran's Gastrointestinal and Liver Disease. 12th ed. Philadelphia, PA: Elsevier; 2026:chap 130.

Review Date: 7/22/2025  

Reviewed By: Todd Eisner, MD, Private practice specializing in Gastroenterology in Boca Raton and Delray Beach, Florida at Gastroenterology Consultants of Boca Raton. Affiliate Assistant Professor, Florida Atlantic University School of Medicine. Review provided by VeriMed Healthcare Network. Also reviewed by David C. Dugdale, MD, Medical Director, Brenda Conaway, Editorial Director, and the A.D.A.M. Editorial team.

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