"Pseudomembranous colitis" is a descriptive term, referring to a pattern of florid injury to the large bowel mucosa. Key microscopic features of pseudomembranous colitis include classic eruptive (“volcano”) lesions with inter-crypt necrosis and ballooned crypts giving rise to a laminated pseudomembrane, which is composed of fibrin, mucin, and neutrophils. The potential causes include Clostridium difficile (C. difficile), Excherischia coli 0157:H7, toxin-producing strains of Escherichia coli, Shigella, fungal infections, diptheria, and cytomegalovirus.

C. difficile overgrowth is the most common cause, and medications that predispose to this include fluoroquinolones, penicillins - such as amoxicillin and ampicillin, clindamycin, and cephalosporins - such as cefixime. Conditions that predispose patients to C. difficile infection include bowel ischemia, recent bowel surgery, uremia, dietary change, change in bowel motility, malnutrition, chemotherapy, shock, and Hirschprung disease. Note: ischemia can cause a pseudomembranous colitis pattern and thus needs to be considered in the differential diagnosis.


See Related Content for references:

1) Iacobuzio-Donahue C, et al. Gastrointestinal and Liver Pathology: A Volume in the Series Foundations in Diagnostic Pathology. Elsevier Inc., 2005, pp. 278-281.

2) Wiland HO, et al., Am J Clin Pathol. 2013 Jun;139(6):730-5.23690114.

3) Cohen SH, et al. Infect Control Hosp Epidemiol. 2010 May;31(5):431-55.