On October 4th at Froedtert Hospital Dr. Lauren Johnson presented a case of acute to sub-acute diarrhea with associated fever and LLQ abdominal pain. The underlying diagnosis was cryptosporidium. What was fascinating about the case was that the infectious workup including stool ova/parasite was negative. It wasn't until random colon biopsies came back positive for "Apical basophilic inclusions most consistent with Cryptosporidium species infection" that the diagnosis was made.
Some key take points from our discussion...
1. 90% - 95% of acute (<2 weeks) diarrhea is infectious. When you start to approach >2 weeks of diarrhea, start to think about other causes.
2. As in most instances, the differential diagnosis is broader in the immunosuppressed patient. This patient was on a JAK2 inhibitor and although not immunosuppressed in the traditional sense these patients should be managed as "functionally immunosuppressed" until proven otherwise. Any patient with diarrhea >14 days or immunosuppressed should be tested for parasite infection (stool O&P or DFA)
3. When you order stool O&P at FMLH, you are asking for a direct microscopic examination of stool specimen looking for cyclospora, isospora, or microsporidium. If you want to test specifically for Giardia lambia or Cryptosporidium, our lab has a more sensitive test that uses Direct Fluorescent Antibody. Due to the nature of intermittent shedding of ova/parasites from the GI tract, O&P or DFA should be ordered and collected 3 times 2-3 days apart to increase sensitivity of the test. That is probably why the DFA came back negative in this case, and it was almost missed except for the colon pathology.
4. Wisconsin Diagnostic Labs has a phenomenal test directory that provides useful information of every laboratory tests available at Froedtert Hospital. Check it out here. 5. If you are a history of medicine fan, you should check out more on the 1993 infamous Cryptosporidium outbreak. Some of our senior GI attendings remember being in Milwaukee during the outbreak and have fascinating stories to share! A link to a JS artical is here.
"Cryptosporidium is my favorite parasite...why?...it got me a week off of high school!"
~Dr. Foy, hematology attending and Milwaukee resident reminiscing on the '93 outbreak
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