Colorectal Services: Colitis

Colitis is an inflammation of the inner lining of the colon that may result in fever, abdominal pain and diarrhea. 

Other symptoms may include bloody bowel movements, chills, dehydration, a constant urge to have a bowel movement and bloating that may be constant or intermittent.

There are many kinds of colitis, including:

  • Infectious colitis (caused by a virus, parasite or bacterial food poisoning)
  • Inflammatory bowel disorders (ulcerative colitis and Crohn's disease)
  • Ischemic colitis (caused by loss of blood supply)
  • Microscopic colitis (invasion of the colon wall by white blood cells)
  • Radiation treatment side effects that affect the large bowel

Treatment depends on the type of colitis. Because some may be more severe and potentially life-threatening, it is important to diagnose the type of colitis when a patient complains of persistent pain and diarrhea — with or without a bloody stool.

For more information about the colitis or to schedule a consultation, please call us at 888-717-4463 or complete our online appointment request form ›

Types of colitis

Infectious colitis

Many varieties of bacteria live in the human gastrointestinal tract. When disease-causing bacteria invade the intestinal system, usually through contaminated food, pain and diarrhea may result. The most common bacterial causes of food-borne illnesses are:
  • Campylobacter
  • E. Coli
  • Salmonella
  • Shigella

Viruses and parasites also can cause infectious colitis. Many of these infections may resolve themselves in a few days, sometimes with the aid of antibiotics. However, antibiotics themselves can upset the natural bacterial balance in the colon.

Rehydration is an important first step in treating all types of colitis. In severe cases, intravenous fluids may be indicated.

Ischemic colitis

As people get older, the arteries that deliver blood to the gastrointestinal tract can narrow and lead to ischemic colitis, either from spasms or blockages. This can be hastened by other conditions, such as dehydration, diabetes, high or low blood pressure, high cholesterol and anemia.

These painful obstructions are the most common vascular disorder of the intestinal tract among the elderly.

Inflammatory bowel disease

Ulcerative colitis typically involves the rectum and the sigmoid colon (the lowermost end of the colon). It may progress over time to the rest of the colon. The cause of ulcerative colitis is believed to be an overactive immune response that attacks the lining of the colon, causing inflammation, abdominal pain and bloody diarrhea.

Crohn's disease usually occurs in the last part of the small intestines or the first part of the colon, although it can involve any part of the gastrointestinal tract, even the esophagus or stomach. It may be characterized by lesions interspersed with healthy tissue along the intestinal lining. Sometimes, when Crohn’s disease primarily involves the colon, symptoms identical to ulcerative colitis may be present.

UC Irvine Health has the region’s only comprehensive program to treat inflammatory bowel disease (IBD).

Learn more about our IBD program and how we treat patients with ulcerative colitis and Crohn’s disease.

Microscopic colitis

Microscopic colitis is a rare type of inflammation of the colon that can be classified as collagenous or lymphocytic colitis.

Patients have more subtle inflammation of the colon lining than in other forms of colitis, and they typically suffer from diarrhea, but without blood present in the stool.

It is more common in older women and is thought to be an auto-immune disease.


To diagnose the type of colitis you have, your physician begins by determining the severity of your symptoms and how long you have had them. It may be important to know if you have traveled somewhere and encountered a viral, parasitic or food-borne infection.

A physical exam can detect high or low blood pressure that could indicate ischemic colitis, as well as possible areas of tenderness, bloating or masses in the abdominal area.

A stool sample may also be tested. If blood is present, your physician may want to screen you for polyps or colon cancer.

Other tests may help determine if you have a low red blood cell count, which could indicate internal bleeding, or a high white blood cell count, which could indicate that your body is fighting an infection.

Your physician also may order additional tests, including:

  • Colonoscopy

This procedure, performed by a trained physician, examines the interior of the colon with fiberoptic or digital camera attached to a thin flexible tube with a light source. The physician looks for signs of inflammation, the presence of polyps or tumors, and may take a tissue biopsy for testing

View a video about colonoscopy ›

  • Computerized tomography (CT) scan

A radiologist scans your colon after a liquid containing barium sulfate is introduced into your colon. The CT scan can provide an X-ray image of your colon with the contrast medium.


Infectious colitis usually resolves itself in a matter of days. Treatment generally involves keeping the patient well hydrated. Sometimes antibiotics or other medications may be prescribed.

Patients with ischemic colitis need to reduce factors that contribute to artery narrowing by ensuring adequate hydration and controlling high blood pressure, high cholesterol and diabetes. In rare cases, severe ischemia can lead to gangrene, which requires surgical intervention.

Patients with inflammatory bowel disease may need to control their disease with long-term medical treatment. In severe cases, an operation may be required.

Patients with microscopic colitis may receive antidiarrheal medications, steroids or immunosuppressant drugs. Only rarely is an operation indicated.