Intestinal amoebiasis, differential diagnosis

The intestines may contain several species of harmless commensal amoeba. Differentiation with these other, non-pathogenic amoebae is important; they include:

• Iodamoeba butschlii: mononuclear cysts, big glycogen supply

• Entamoeba hartmanni: small cysts with four nuclei

• Endolimax nana: smaller round or oval cysts with 2-4 nuclei (measuring 6-12 m) and slow-moving trophozoites (L.: limax = slug)

• Entamoeba coli: larger cysts containing 1, 2, 4 or 8 nuclei

• Entamoeba dispar is a special case (see above)

In dysentery it is important to distinguish between bacillary and amoebic dysentery since their treatment is completely different. A diagnosis may be made clinically, but it is best to confirm this by microscopy as there is partial clinical overlap of the two diseases. Balantidium coli is a pathogenic ciliate which can cause severe colitis.

This illness is very similar to intestinal amoebiasis and the diagnosis can only be made by coprologic examination. Treatment is with tetracyclines. Pseudomembranous colitis is caused by infection with toxicogenic Clostridium difficile. These bacteria can be selected out and can proliferate after administration of certain antibiotics.

Metronidazole is a good treatment in this case. Vancomycin is equally effective, but will not be given in third world countries in view of its high cost. A related bacterium, Clostridium perfringens, can cause necrotising colitis (necrotic enteritis, Pigbel syndrome). This disorder has an acute course and is very severe. Sometimes gonococcal proctitis can be confused with amoebiasis. There are then no proximal intestinal lesions and culture of the mucus provides a diagnosis. Crohn’s disease and ulcerative colitis are rare in the tropics. Radiology and biopsies are essential for their diagnosis.

Category: Medicine Notes