Question 27

Outline  the diagnostic  features of pseudomembranous colitis and list the likely causes in patients  in Intensive Care.

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College Answer

Diagnostic features include: Watery Diarrhoea, Bloody diarrhoea, Pseudomembranes (may be passed with stool or may be visible on bowel mucosa on colonoscopy), Recent or current course of antibiotics, Abdominal tenderness, fever, increased WCC. Clostridium difficile infection can be asymptomatic.

Diagnosis confirmed by detection of clostridium difficile toxins (A &/or B) in stool (toxin present in 95% of patients with pseudomembranous colitis).

Other features on investigations: Plain AXR - mucosal thickening, "thumbprinting", or colonic distension; CT abdo – wall thickening, irregular bowel wall margin, pericolonic stranding, ascites. Features of complications include: electrolyte disturbances (low K, normal anion gap acidosis due to bicarbonate loss), hypoalbuminaemia, dehydration, toxic megacolon, perforation, pneumoperitoneum, possibly progressing to shock MOF.

Likely causes in patients in Intensive Care: Clostridium difficile infection; Overgrowth of clostridium due to eradication of other organisms; Antibiotics – particularly reported following clindamycin, cephalosporins (particularly 3rd generation), ampicillin/amoxycillin but can occur after any (less likely with ticarcillin/clavulanate, aminoglycosides, quinolones). More likely following shock and decreased gut perfusion, renal failure and in the old and debilitated or in patients with immunocompromise such as haematological malignancy or HIV infections.


C.difficile infection is a favourite of the college, and appears frequently in the papers.

For instance, Question 3 from the first paper of 2013 asks even more detailed questions.

To bring together all the previously exmained aspects of pseudomembranous colitis, a summary ofC.difficile infection is available in the Required Reading section.

Diagnostic features:

  • Abdominal pain
  • Loose stools
  • History of broad spectrum antibiotics, particularly Clindamycin
  • Characteristic "thumbprinting" of bowel on plan Xrays
  • Inflamed appearance of bowel on CT
  • Direct confirmation of pseudomembranes on colonoscopy
  • C.difficile toxin A or B on stool PCR
  • Toxic megacolon
  • Perforation and pneumoperitoneum
  • Fever > 38°
  • Renal failure

Causes of pseudomembranous colitis in ICU:

Surely, the college - being composed of people with a certain respect for specificity- would be asking for the specific causes of pseudomembranous colitis. Of which there really is only one: C.difficile. The rest of the "likely causes" mentioned in the model answer are associated factors. The use of clindamycin does not "cause" this disease.

That said, not all pseudomembranous colitis is due to C.difficile infection.

Alternative pathogens include:

  • Strongyloides stercoralis
  • Staphylococcus aureus
  • Clostridium perfringens
  • Yersinia
  • CMV
  • Entamoeba
  • Listeria
  • All the enterohaemorrhagic diarrhoea organisms:
    • Salmonella
    • Shigella
    • Campylobacter
    • E.coli

Factors associated with C.difficile enterocolitis are as follows:



Loo, Vivian G., et al. "Host and pathogen factors for Clostridium difficile infection and colonization." New England Journal of Medicine 365.18 (2011): 1693-1703.


Thomas, Claudia, Mark Stevenson, and Thomas V. Riley. "Antibiotics and hospital-acquired Clostridium difficile-associated diarrhoea: a systematic review." Journal of antimicrobial chemotherapy 51.6 (2003): 1339-1350.


Anand, Ajay, and Aaron E. Glatt. "Clostridium difficile infection associated with antineoplastic chemotherapy: a review." Clinical Infectious Diseases 17.1 (1993): 109-113.


Cunningham, R., et al. "Proton pump inhibitors as a risk factor for Clostridium difficilediarrhoea." Journal of Hospital Infection 54.3 (2003): 243-245.


Pépin, Jacques, Louis Valiquette, and Benoit Cossette. "Mortality attributable to nosocomial Clostridium difficile–associated disease during an epidemic caused by a hypervirulent strain in Quebec." Canadian Medical Association Journal 173.9 (2005): 1037-1042.


Cunney, Robert J., et al. "Clostridium difficile colitis associated with chronic renal failure." Nephrology Dialysis Transplantation 13.11 (1998): 2842-2846.


Surawicz, Christina M., et al. "Guidelines for diagnosis, treatment, and prevention of Clostridium difficile infections." The American journal of gastroenterology 108.4 (2013): 478-498.


Henrich, Timothy J., et al. "Clinical risk factors for severe Clostridium difficile–associated disease." Emerging infectious diseases 15.3 (2009): 415.


FujitaniMD, Shigeki, W. Lance GeorgeMD, and A. Rekha MurthyMD. "Comparison of clinical severity score indices for Clostridium difficile infection."Infection Control and Hospital Epidemiology 32.3 (2011): 220-228.


Janvier, Jack, Susan Kuhn, and Deirdre Church. "Not all pseudomembranous colitis is caused by Clostridium difficile." The Canadian Journal of Infectious Diseases & Medical Microbiology 19.3 (2008): 256.