Pseudomembranous colitis laboratory findings
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Editor-In-Chief: C. Michael Gibson, M.S., M.D. [1]
Laboratory Findings
In order to make the diagnosis, it is, of course, essential that the treating physician be aware of any recent antibiotic usage. The disease may occur as late as one or two months after the use of antibiotics. Although there is some relationship between dose/duration of antibiotic and likelihood of developing pseudomembranous colitis, it may occur even after a single dose of antibiotic. In fact, the use of single-dose antibiotic is a common practice in surgical patients for whom such a treatment is often given just prior to surgery in order to prevent infection at the surgical site. Hence, even though unlikely to cause pseudomembranous colitis on a per-case basis, single-dose antibiotic treatment, by virtue of the large number of patients receiving such, is an important cause of pseudomembranous colitis.
Prior to the advent of tests to detect the Clostridium difficile toxin, the diagnosis was most often made by colonoscopy or sigmoidoscopy. The appearance of "pseudomembranes" on the surface of the colon or rectum is diagnostic of the condition. The pseudomembranes are composed of inflammatory debris, white blood cells, etc.
Although colonoscopy and sigmoidoscopy are still employed, stool testing for the presence of Clostridium difficile toxin is now often the first-line diagnostic appraoach. Usually, only two toxins are tested for - Toxin A and Toxin B - but the organism produces at least several others. It is, perhaps, for this reason that some people who seem to have pseudomembranous colitis (i.e. a history of antibiotic use, non-bloody diarrhea, and the presence of pseudomembranes seen on colonoscopy) do not have detectable C. diff toxin in their stool.