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Colitis (cont.)

Colitis Diagnosis

The diagnosis of colitis begins with a thorough history by a physician or health care practitioner. Since the symptoms are usually abdominal pain and diarrhea, it is important to learn about the onset and duration of symptoms, and any other complaints or symptoms the patient may have. Since most causes of diarrhea are relatively benign and self-limiting, questions may be asked to search for some of the causes listed above.

An important concern is whether there is blood in the bowel movement (stool). While this may lead to the diagnosis of colitis, colon cancer is another important cause of blood in the stool, and this symptom should not be ignored (as mentioned previously, blood with a bowel movement or in the stool is not normal and should not be ignored).

Some questions asked of the patient may include:

  1. the time of onset of symptoms,
  2. the duration of pain,
  3. the frequency of diarrhea, and
  4. whether there are any other associated complaints.

Other questions may include lifestyle, especially if an infectious cause is being considered. Recent travel, unusual diet, or the use of noncommercial water (for example, drinking from a well or river water on a camping trip) may point the diagnosis to bacterial infections such as Shigella, Campylobacter, or Yersinia; or parasite infections such as giardia. Recent use of antibiotics may direct the health care practitioner to consider Clostridium difficile as the cause.

The past medical history is also important to assess the risk factors for peripheral vascular disease or narrowing of the arteries. These include smoking, high blood pressure, high cholesterol, and diabetes. This may give direction to explore ischemic bowel as the cause for colitis.

Physical examination will focus on the abdomen. The physician will feel for areas of tenderness, for masses, or abnormally enlarged organs like the liver, spleen, and kidney.

While unpleasant, the rectal examination is of utmost importance. Using a finger, the physician feels inside the rectum, trying to find a mass or tumor. As well, the color and consistency of stool can be evaluated and if it is not grossly bloody, can be tested for occult blood (blood that is present but cannot be seen with the naked eye).

Vital signs are an important part of the physical examination. Temperature, blood pressure, pulse, and respiratory rate will help guide the direction of testing. If the vital signs are not stable, that is the blood pressure is low or the pulse rate too fast, a crisis may be imminent. The physician may need to intervene acutely and delay some of the diagnostic evaluation until the patient is stabilized. Orthostatic vital signs, where the blood pressure and pulse rate are taken both lying and standing may assist with detecting dehydration.


Blood testing will help assess the stability of the patient and look for potential issues associated with colitis.

  • A complete blood count (CBC) will assess the red blood cell count, the white blood cell count, and the number of platelets. The red blood cell count will help define the amount of bleeding. White blood cell counts elevate when the body is undergoing stress including the stress of infection. Platelets help blood to clot, so knowing the platelet number in a patient with bleeding is useful.
  • Electrolyte abnormalities can occur with diarrhea. Low sodium and potassium levels may be seen and may cause symptoms far removed from the initial colitis complaints.
  • Kidney function may be assessed by measuring the BUN (blood urea nitrogen) and creatinine levels.
  • Stool samples may be collected for culture, looking for infection as the cause of colitis. The history will assist the health care practitioner decide the tests to order and what cultures would be appropriate.


If a specific cause of colitis is not readily apparent, then colonoscopy may be considered. A gastroenterologist will insert a long flexible camera into the anus and examine the full length of the colon. The appearance of the colon by itself may be enough to make the diagnosis. Biopsies (small pieces of tissue) may be taken from the lining of the colon and examined by a pathologist (a medical doctor specializing in the diagnosis of tissues) to help confirm the diagnosis. Microscopic colitis (lymphocytic and collagenous) can only be diagnosed with biopsy of the affected area.

Colonoscopy is an essential cancer screening test and is especially important for those patients who have had blood in their stool that cannot be explained by another diagnosis.


Computerized tomography (CT) may be used to image the colon and the rest of the abdomen. Different types of colitis have distinctive patterns that may help a radiologist recognize a specific diagnosis. A CT scan may be ordered urgently if the history and physical examination performed by the health care practitioner leads to concern that an urgent or emergent problem exists that may require surgery.

On occasion a barium enema or other imaging tests may be used to evaluate the anatomy of the colon.

Medically Reviewed by a Doctor on 5/1/2014

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Colitis »

Colitis is an inflammation of the colon. It may be associated with enteritis (inflammation of the intestine) and/or proctitis (inflammation of the rectum).

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