Caught in the act . . . a case of fulminant amoebic colitis

Entamoeba histolytica is a common, well-recognized pathogenic amoeba, associated most often with intestinal but also extra-intestinal infection. It is found worldwide but has a higher incidence in countries with inadequate infrastructure to limit faecal–oral transmission. Clinical disease can vary from asymptomatic colonization to invasive intestinal amoebiasis; dissemination most commonly occurs to the liver but can affect other body sites (Haque et al., 2003). When diagnosed early, treatment of colonic disease is generally straightforward and the prognosis is good. Here, we report an encounter with a patient in whom diagnosis was delayed resulting in progression to fulminant colitis.


Introduction
Entamoeba histolytica is a common, well-recognized pathogenic amoeba, associated most often with intestinal but also extra-intestinal infection.It is found worldwide but has a higher incidence in countries with inadequate infrastructure to limit faecal-oral transmission.Clinical disease can vary from asymptomatic colonization to invasive intestinal amoebiasis; dissemination most commonly occurs to the liver but can affect other body sites (Haque et al., 2003).When diagnosed early, treatment of colonic disease is generally straightforward and the prognosis is good.Here, we report an encounter with a patient in whom diagnosis was delayed resulting in progression to fulminant colitis.
Post-operatively the patient was admitted to intensive care and progressively improved.Renal and liver function returned to baseline over several days.Operative histology (Fig. 1) revealed changes consistent with extensive infection from E. histolytica.A 10-day course of oral metronidazole 600 mg every 8 h was administered, followed by paromomycin 500 mg every 8 h for 7 days.A liver ultrasound was performed to exclude extra-intestinal disease.Amoebic serology by indirect haemagglutination was strongly positive (titre 1 : 4096).Clinical improvement continued and he was discharged from hospital feeling well 2 weeks after his initial presentation.He subsequently returned to India.

Discussion
E. histolytica infection may be asymptomatic, cause dysentery or disseminate, most commonly to the liver.Humans are the primary known reservoir, and transmission occurs via the faecal-oral route (Stanley, 2003).There are several closely related Entamoeba spp. that are morphologically indistinguishable, with Entamoeba dispar traditionally thought to be non-pathogenic.Recent DNA evidence is Following ingestion of cysts, excystation occurs within the intestinal lumen and trophozoites develop.In the majority of cases, this results in self-limiting, asymptomatic infection.Colitis occurs when they penetrate the intestinal mucous layer, resulting in an inflammatory response (Haque et al., 2003).Delayed diagnosis or failure to initiate prompt effective therapy can result in progression to severe fulminant colitis with a high morbidity and mortality (Gupta et al., 2009).One recent case series (Ortiz-Castillo et al., 2012) of 24 patients from an endemic area described a mortality rate of 50 %, with 20 patients requiring surgery within 24 h of presentation.An older study of 55 patients (Takahashi et al., 1997) reported a co-existent liver abscess in 54 % of patients and had a higher mortality of 89 %.
Despite limitations, the mainstay of diagnosis worldwide remains stool microscopy.Antigen detection and PCRbased diagnostics are being increasingly utilized where available, and are more sensitive and specific.Serology is used mainly in extra-intestinal disease but does not reliably differentiate between current and past infection; more accurate enzyme immunoassay kits are commercially available and have largely replaced the indirect haemagglutination test used by our laboratory (Tanyuksel & Petri, 2003;Santos et al., 2013).
Treatment with metronidazole or tinidazole is generally curative but is active against the trophozoite stage only; paromomycin is required to prevent relapse by eliminating cyst carriage (Pritt & Clark, 2008).Broad-spectrum antibiotics are often indicated in fulminant disease where bacterial translocation across the damaged intestinal wall can occur, and therapeutic aspiration of a liver abscess is occasionally required as adjunctive therapy (Petri, 2003).Nitazoxanide is a possible treatment alternative; however, its role has not been well defined (Rossignol et al., 2007).
In summary, we have described a patient with amoebic colitis who progressed to fulminant disease requiring urgent laparotomy and hemicolectomy.Our patient had seen a medical practitioner twice before presenting to our institution; no investigations had been performed and empiric amoxicillin had been prescribed.Even after his deterioration, the diagnosis of amoebic colitis had not been considered until operative histology was available, which was several days postoperatively.Despite this, fortunately he survived with minimal sequelae.Given increasing international migration and travel, clinicians worldwide need to maintain a high index of suspicion of this condition, particularly in patients originating from endemic areas, to ensure early diagnosis and appropriate treatment to avoid complications.

Fig. 1 .
Fig. 1. (a, b) Haematoxylin and eosin stains of the caecum of the patient showing the classic flask-shaped colonic ulcer with adjacent normal colonic tissue.(c, d) Haematoxylin and eosin stained high-power images showing multiple trophozoites invading the colonic wall, including one that appears to be caught in the act of ingesting an erythrocyte (arrow in d).Magnification, 640 (a); 6100 (b); 6400 (c); 6600 (d).