Fulminant amebic colitis mimicking pseudomembranous colitis

 CommentaryThe differential diagnosis of abdominal pain and diarrhea is vast but made easier, as in this case, when sigmoidoscopy shows typical abnormalities—but typical of what? We have come to appreciate that the body's reaction to a wide variety of physical insults is limited and that one disease process often can resemble another. Thus, in this case, we have the appearance of pseudomembranous colitis, most commonly caused by Clostridium difficile. However, do these really look like pseudomembranes? Not having been at the procedure and being limited to looking at the one beautiful illustration in this Focal Point, I think these lesions do not appear like pseudomembranes, but rather ulcers with overlying exudate. Am I splitting this hair too finely? Probably. Histologically, a pseudomembrane typically appears like a volcano erupting out from the glandular epithelium and spilling into the colonic lumen, while retaining some attachment to the subjacent tissue. Hence, a pseudomembrane tends to project above the underlying mucosal defect. The yellowish-white material in question here seems to be within the ulcers, an appearance suggesting, to me, that they are not really pseudomembranes, but rather exudate. Even if they were pseudomembranes, however, the principle of limited disease expression mentioned above is still respected, and pseudomembranes can be seen with various colitides in addition to C. difficile, including ischemic colitis and, yes, amebic colitis. Biopsy is critical for diagnosis and typically reveals the causative trophozoites. Amebic trophozoites and their toxins usually respect the integrity of the muscularis propria, except in cases such as this in which toxic colitis results in myonecrosis with multiple ulcers and perforations. It is never comforting to see free air after an endoscopy, but this finding prompted the appropriate care, namely urgent colectomy. Mortality rates in amebic colitis range from approximately 2% to 9%, although in the presence of toxic colitis, mortality is increased to 40%, and, in some series, operative mortalities approach 80%. Amebic colitis is no longer an exotic disease; think of it in world travelers, in patients with immunocompromise—diabetics, alcoholics, and patients receiving chemotherapy—also the patient suspected of having Crohn's disease or ulcerative colitis, who is not getting better, especially when being treated with antidiarrheal agents and corticosteroids. The word amoeba comes from the Greek amoibe, to change. Presumptive diagnosis based on a lesion's appearance is important for initial therapy, but only objective data enable definitive diagnosis and specific therapy.Lawrence J. Brandt, MDAssociate Editor for Focal Points

PII: S0016-5107(09)02445-6

doi:10.1016/j.gie.2009.09.009

© 2010 American Society for Gastrointestinal Endoscopy. Published by Elsevier Inc. All rights reserved.