Clinical History:
- Following heart transplantation for idiopathic dilated cardiomyopathy, this 40-year-old woman developed acute cellular rejection, as shown on endomyocardial biopsy. Her immunosuppressive therapy was increased. She then developed bacterial and fungal sepsis. She was treated with antimicrobial therapy, including clindamycin. She then developed diarrhea. A colonoscopy was performed (image 3.1). Her condition worsened, she became toxic, and a colectomy was performed, with the appearance seen in image 3.2. The microscopic appearance is seen in images 3.3 and 3.4.
- What is the diagnosis?
This is pseudomembranous colitis. In some cases the small intestine can also be involved to produce pseudomembranous enterocolitis.
- What laboratory testing can be performed to make the diagnosis?
A stool culture along with assay for C. difficile toxins was done and both were positive.
- What is the pathogenesis of this lesion?
C. difficile disease ranges from mild diarrhea to fulminant pseudomembranous colitis. This disease is produced by mucosal injury from toxins A and B of Clostridium difficile. These toxins cause release of substance P which elicits fluid secretion and neutrophil infiltration by binding to a G-protein-coupled receptor. C. difficile is a normal gut commensal organism that can overgrow with broad spectrum antibiotic therapy (clindamycin, lincomycin, ampicillin, etc.) and lead to extensive mucosal injury. Overgrowth of other organisms such as Candida and Staphylococcus can produce similar findings. Additional risk factors for pseudomembranous colitis include: age >65 years, antineoplastic chemotherapy, length of hospital stay, enemas, nasogastric tubes, gastrointestinal surgery and antiperistaltic drugs.
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