Amoebic appendicitis

The aetiology was established histo-logically, as no distinctive clinical or macroscopic features were noted. The appendices showed extensive coagulative necrosis of the mucosa, submucosa and muscularis propria and invasion of the wall by variable numbers of amoebae with ingested blood cells. Inflammation secondary to perforation was evident in the serosa and the mesoappendix, but no significant inflammation was seen in the inner layers of the wall (Box).

Coagulative necrosis of the appendiceal wall was seen in all the cases. In fact, in some of the cases the diagnosis was suspected on seeing this distinctive coagulative necrosis and the amoebae were only found later. Thus, we believe this type of necrosis, which has not been previously emphasised in the literature, to be characteristic of the condition.

Amoebiasis is rare in a developed country like Australia. The infection is generally acquired during travel to endemic parts of the world. However, case reports of invasive amoebiasis in Indigenous Australians who have not travelled outside Australia have been previously reported.1,2 Immigration, immunosuppression and poor sanitation are other settings in which amoebiasis can be seen.3

The finding of six cases of amoebic appendicitis in Indigenous Australians in the Northern Territory in a 15-month period is significant, as appendicitis is a very rare manifestation of the disease. McCarthy et al, in a recent MJA article,2 highlight the potential public health significance of endemic invasive amoebiasis because of its high transmissibility in settings where hygiene may be suboptimal. We agree with this and believe in selective screening and appropriate treatment of at-risk contacts of the patients, as prolonged latency between infection and disease is well documented.3

Cross-section of appendix

Cross-section of appendix with coagulative mural necrosis and secondary serosal inflammation (haematoxylin and eosin [H&E] original 1×). Numerous amoebae in clear spaces, some with ingested blood cells, are seen in the insert (H&E original 40×).