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  • Surgical Pathology Criteria

    Pseudomembranous Colitis


    • Colitis secondary to disruption of normal bowel flora

    Alternate/Historical Names

    • Antibiotic associated pseudomembranous colitis or enterocolitis
    • Clindamycin associated pseudomembranous colitis or enterocolitis

    Diagnostic Criteria

    • Damage is due to toxin A produced by Clostridium difficile in bowel lumen
      • Not due to tissue invasion by bacteria
    • Damage is centered on the crypts
      • Frequently patchy with abrupt involvement of 2-10 or more crypts surrounded by normal crypts
      • Entire length of crypt is usually involved
      • Affected crypts denuded and distended and appear to erupt into the bowel lumen
        • Resembles an erupting volcano
      • Lamina propria between involved crypts frequently remains intact
    • Pseudomembrane is formed by necrotic epithelial cells, mucus, fibrin and neutrophils
      • Neutrophils and fibrin frequently appear linear in pseudomembrane
      • Pseudomembrane may not always be identified on biopsy
    • Signet ring cells may be seen in rare cases
      • Confined to crypts and epithelial surface
      • No infiltration into lamina propria
      • Cells have small bland nuclei
    • Muscularis mucosae, submucosa and muscularis propria are not primarily involved
      • Severe cases may result in complete destruction of mucosa leading to toxic megacolon
    • Because of patchy involvement, fragments of pseudomembrane may be present without mucosal changes
      • This finding should prompt additional sections and/or clinical correlation

    Robert V Rouse MD
    Department of Pathology
    Stanford University School of Medicine
    Stanford CA 94305-5342

    Original posting : November 11, 2009

    Differential Diagnosis

    Chemical / Iatrogenic Colitis Antibiotic-associated Pseudomembranous Colitis
    Diffuse necrosis and sloughing of superficial mucosa Frequently patchy involvement of 2-10 crypts with normal surrounding crypts
    Mucosal microthrombi and hemorrhage Not associated with microthrombi or hemorrhage
    History of endoscopy or introduction of foreign substance History of antibiotic therapy
    Both may form a pseudomembrane


    Pseudomembranous Colitis Enterohemorrhagic E coli Colitis
    Endoscopic pseudomembrane Pseudomembrane only microscopic
    Necrotic crypt epithelium erupts into lumen to form pseudomembrane Entire upper mucosal layer may slough into lumen to form pseudomembrane
    Hemorrhage is not prominent Prominent hemorrhage and capillary thrombosis
    C difficile titers elevated E coli O157:H7 identified by culture
    Associated with antibiotic therapy Not associated with antibiotic therapy


    Pseudomembranous Colitis Ischemic Colitis
    Diffuse Localized, may form a mass
    No hyanization of lamina propria Hyalinized lamina propria
    Occasional atrophic crypts Atrophic microcrypts common
    Usually only superficial necrosis Necrosis frequently transmural
    C difficile titer elevated C difficile titer negative
    Associated with antibiotic therapy Not associated with antibiotic therapy


    • Usually follows treatment with clindamycin, ampicillin or third generation cephalosporins
      • Rare cases occur in the absence of antibiotic therapy
      • Disruption of normal flora allows overgrowth of Clostridium difficile, and rarely C perfringens


    • Noffsinger A, Fenoglio-Preiser CM, Maru D, Gilinisky N.  Gastrointestinal Diseases, AFIP Atlas of Nontumor Pathology, First Series, Fascicle 5, 2007.
    • Signet-ring cells associated with pseudomembranous colitis. Am J Surg Pathol. 1996 May;20(5):599-602.
    Printed from Surgical Pathology Criteria: http://surgpathcriteria.stanford.edu/
    © 2005  Stanford University School of Medicine