Invasive amoebiasis: a review of Entamoeba infections highlighted with case reports

Abstract

Entamoeba histolytica infections of the gastrointestinal tract are common in the developing world but rare in North America. The authors present two cases: one involving an individual who had not travelled to an endemic area and another involving an individual who was born in Bulgaria. Both presented with severe abdominal pain and diarrhea. Endoscopic assessment revealed scattered colonic ulcerations and one patient was found to have a liver abscess on imaging. Stool ova and parasite studies were negative in both cases and both were diagnosed on review of colonic biopsies. On review of all Entamoeba cases in the Calgary Health Zone (Alberta), ova and parasite analysis found an average of 63.7 Entamoeba cases per year and a pathology database review revealed a total of seven cases of invasive E histolytica (2001 to 2011). Both patients responded well to antibiotic therapy. E histolytica should be considered in new-onset colitis, especially in individuals from endemic areas.

Figure 1)

Cases of Entamoeba from stool ova and parasite analysis in the Calgary Health Region (Alberta) according to year (A) and age (B)

Figure 2)

Transverse (A) and coronal (B) computed tomography images of the abdomen demonstrating liver abscesses (black arrows) and colonic wall thickening (yellow arrows) on initial presentation of patient 1. Computed tomography images of the abdomen demonstrating worsening colitis (arrows), pericolic stranding and fluid on day 6 of hospital admission of patient 1 (C and D)

Figure 3)

Colonoscopic imaging of patient 1 (A and B) and patient 2 (C and D) demonstrating classic amoebic ulceration in both patients (arrows)

Figure 4)

A and B Colon biopsies of patient 1. Alcian blue periodic acid Shiff (PAS) stain (A: original magnification ×40, B: higher magnification of A), arrows indicate Entamoeba histolytica trophozoites (many do not have arrows). C and D Patient 2 (hematoxylin and eosin stain C: original magnification ×100, D: higher magnification C, arrows indicate PAS-positive E histolytica trophozoites (many do not have arrows)