Critical Care Medicine-Gastrointestinal, Nutrition and Genitourinary Disorders>>>>>Diagnostic and Management Modalities
Question 3#

An 85-year-old male who was recently treated for an upper respiratory tract infection presented 2 days ago with abdominal pain. On abdominal examination, he has tenderness to palpation with mild distention but no signs of peritonitis. On admission, the WBC was 25 cell/mL and now it is 18 cell/mL. Urinalysis does show bacteria and the initial diagnosis is a UTI. Cultures have been sent. Chest X-ray does not show any evidence of pneumonia. He starts to develop hypotension on the floor with oliguria requiring 2 L of crystalloid. A request is made to transfer the patient to the ICU. The nurse notes that in the past 24 hours, he has had four episodes of diarrhea. Stool was sent for GDH (glutamate dehydrogenase) and Toxin A and B. GDH was negative, but the Toxin A/B was positive. She asked the intern on the floor to start IV Flagyl for a presumed Clostridium difficile infection, but the intern has not started it yet. Aside from the sepsis guidelines and ICU care, what is the NEXT step to address a possible C. difficile infection?

A. Hydration, bowel rest, continuing current empiric antibiotics, and monitoring her symptoms
B. Start IV Flagyl because the patient is positive for Toxins and obtain a KUB
C. Send stool for nucleic acid amplification testing then start IV Flagyl and obtain a KUB
D. Start IV Flagyl and PO Vancomycin and obtain a KUB

Correct Answer is C


Correct Answer: C

The laboratory approaches to diagnosis of C. difficile is followed when there is a suspicion for C. difficile infection. Generally, this infection is suspected when there is acute onset, and clinically significant diarrhea (≥ three loose stools over 24 hours) and risk factures such as recent antibiotic use, hospitalization, and advanced age. This patient has all the criteria for a suspected C. difficile infection. The stool was appropriately sent for ELISA Immunoassay for GDH antigen and Toxins A and B. If both are positive, then testing is consistent with C. difficile infection. If both are negative, then testing is not consistent with C. difficile infection. However, if one test is positive and the other is negative, then that is considered an intermediate test result. Then the stool must be sent for Nucleic acid amplification test (NAAT). The laboratory will then perform a NAAT for tcdB and tcdC genes. If this test is positive, then the patient is considered to have C. difficile infection. If this test is negative, then the patient is considered to not have the infection. It is important to note that the NAAT testing should ideally be sent before C. difficile infection treatment. However, if there is a high suspicion for the infection and the patient is showing signs sepsis, then early treatment is essential. With the abdominal pain and signs of early septic shock, it is important to get a KUB to rule out signs of toxic megacolon on imaging. A patient with signs of peritonitis will need an urgent surgical evaluation.


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