Clostridium Difficile Colitis (cont.)
How is C. difficile colitis diagnosed?
History
A history of antibiotic use is important in the diagnosis of C. difficile
colitis. Patients taking antibiotics (or recently having taken antibiotics) who
develop abdominal pain, cramps and
diarrhea are usually tested for C. difficile
infection. However, doctors do not always wait for the appearance of diarrhea to
start testing for C. difficile since in rare instances C. difficile can cause
abdominal pain and tenderness without diarrhea.
Laboratory tests
Patients with C. difficile colitis often have elevated
white blood cell counts
in the blood, and, in severe colitis, the white blood cell counts can be very
high (20,000 to 40,000). Patients with C. difficile colitis also often have
white blood cells in their stool when a sample of stool is examined under a
microscope. Elevated white blood cell counts and white blood cells in the stool,
however, only demonstrate that there is colitis and not that the cause of the
colitis is C. difficile. More specific tests are necessary to determine whether
C. difficile is the cause of the colitis.
The most widely used test for diagnosing C. difficile colitis is a test that
detects toxins produced by C. difficile in a sample of stool. There are two
different toxins, toxin A and toxin B, both capable of causing colitis. Accurate
tests for both toxins are available commercially for use in all laboratories.
Unfortunately, like most tests in medicine, these tests for toxins are not
perfect; both false positive tests (finding toxins when there is no C.
difficile) and false negative tests (not finding toxins when C. difficile is
present) can occur. Therefore, other tests such as flexible sigmoidoscopy and
colonoscopy often are necessary to look for pseudomembranes that are
characteristic of C. difficile colitis.
Flexible sigmoidoscopy and
colonoscopy
Flexible sigmoidoscopy is an examination in which a doctor inserts a flexible
fiberoptic tube with a light and a camera on its end into the rectum and sigmoid
colon. (The sigmoid colon is the segment of the colon that is closest to the
rectum.) In most patients with C. difficile colitis, the doctor will find
pseudomembranes in the rectum and the sigmoid colon. However, some patients with
C. difficile colitis will have pseudomembranes only in the right colon (the
segment of the colon farthest from the rectum). Patients with pseudomembranes
confined to the right colon require colonoscopy in order to see the
pseudomembranes. (A colonoscope is a longer version of the flexible
sigmoidoscope that is long enough to reach the right colon.)
X-Rays
X-ray examinations and computed tomography (CT) examinations of the abdomen will
occasionally demonstrate thickening of the wall of the colon due to
inflammation, but these x-ray findings also are non-specific and only
demonstrate that colitis is present. They do not demonstrate the cause of the
colitis, for example, C. difficile.
Next: How is Clostridium difficile colitis treated? »
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