amoebiasis is an infectious disease caused by entamoeba histolytica , and is the second leading cause of death from parasitic disease worldwide ( 1 ) .
it is commonly acquired by ingestion of contaminated food or water and is therefore endemic in developing countries with poor sanitation .
ten percent of the world s population become infected , 90% of which are asymptomatic ( 2 ) .
we present a case of amoebic colitis that caused diagnostic confusion by mimicking a colonic carcinoma .
a 63 year - old woman presented to hospital with a 5 weeks history of colicky right upper quadrant abdominal pain , abdominal distension and constipation
there was no history of recent foreign travel , but she had travelled to the middle east 6 months prior to admission .
she had had a normal colonoscopy performed for a change in bowel habit 2 years previously , and an abdominal ultrasound scan performed at the onset of her symptoms was also normal , apart from a 1.5 cm cyst in the liver . on examination she was dehydrated and was tender in the right iliac fossa and right upper quadrant .
she had a raised white blood cell count ( 13.4 10 * 9/l ) and crp ( 310mg / l ) , but all other blood tests were within normal limits .
her chest x - ray showed blunting of the left costophrenic angle and her abdominal x - ray showed multiple dilated small bowel loops with faecal loading in the descending colon .
she was started on intravenous tazobactam and piperacillin and a ct scan of her abdomen and pelvis was performed .
this showed a low attenuation lesion in the left lobe of the liver with surrounding inflammation consistent with a liver abscess ( figure 1 ) , as well as wall thickening in the ascending colon that extended into the caecum and terminal ileum ( figure 2 ) .
ct image demonstrating low attenuation lesion in the left lobe of the liver with surrounding inflammation consistent with a liver abscess gross appearance of caecum and ascending colon showing ulcerated and polypoidal amoebic lesions mimicking colonic mucosal tumours the differential diagnosis at this stage included appendicitis , colonic crohn s disease , and colorectal neoplasia . due to the possibility of colonic malignancy
an inflammatory mass involving the right colon was confirmed , and so the patient underwent a right hemicolectomy and drainage of liver abscess .
she was continued on postoperative antibiotics and apart from a short period of paralytic ileus , she progressed well .
macroscopically , there were inflammatory exudates on the surface of the caecal and terminal ileal mucosa , as well as thickening and ulceration in the caecum .
there were also multiple raised ulcerated lesions in the ascending colon ( figure 3 ) .
microscopically , necrotic and haemorrhagic material was noted , with the base of the ulcers heavily infiltrated with inflammatory material involving the mucosa and submucosa .
there were also amoebae parasites present within the inflammatory cellular exudates in most of the ulcers examined microscopically , but there was no granuloma formation , dysplasia or malignancy seen .
h&e stained histological section of amoebic abscess in the colonic wall demonstrating entamoeba histolitica parasites ( arrowed ) .
patients with intestinal amoebiasis are usually asymptomatic , but it can lead to colitis , abscess formation , perforation and rarely a tumour - like mass in the colon termed an amoeboma .
initially abdominal pain and diarrhoea predominate , with bloody diarrhoea marking a progression to colitis that typically involves the caecum , ascending or sigmoid colon .
an amoeboma is suggested by pain and swelling in the right iliac fossa , or symptoms of bowel obstruction .
the most common extraintestinal manifestation of amoebiasis is liver abscess , due to parasites gaining entry into the portal circulation .
there were 110 reported cases of entamoeba 
 histolytica infection in england and wales in 2009 ( 3 ) .
there is usually a history of recent travel to an endemic area . in the present case ,
the patient did not report a significant recent travel history , nor symptoms of diarrhoea .
it is likely she had previously travelled to an endemic region and had developed an asymptomatic carrier state .
the typical features of amoebic colitis on ct are flask shaped ulcers with intramural dissection , whereas amoebic liver abscess typically causes well rounded , low density lesions with a clear fluid level .
amoeboma formation usually shows a localised hyperplastic granulomatous reaction forming an inflammatory mass that macroscopically resembles colon cancer .
however , the association of colonic mass and liver abscess suggests an inflammatory rather than neoplastic aetiology , as there are few reports of abscess formation within colorectal liver metastases .
serology aids the diagnosis of amoebiasis , being positive in 95% patients with amoeboma or hepatic amoebiasis , but only 60% in patients with amoebic colitis(4 ) .
diloxanide furoate is given as a 10 day course in addition to eliminate luminal cysts .
surgery is only used when medical therapy fails , in rupture of liver abscess , or when there is diagnostic uncertainty .
this case highlights the diagnostic uncertainty that may occur in patients with amoebic colitis due to its ability to mimic colonic carcinoma , particularly if there is no definite recent history of travel to an endemic area .
it highlights the importance of good history taking , in particular a thorough travel history , in patients with unusual intra - abdominal infections .
 intestinal entamoeba histolytica infection in the uk is rare but it can lead to colitis , abscess formation , colonic perforation and rarely amoeboma . although most patients are asymptomatic , it can present with a wide range of gastrointestinal symptoms depending on the phase of the infection . 
 we present a case of amoebic colitis that caused diagnostic uncertainty by mimicking a colonic carcinoma . 
INTRODUCTION
CASE REPORT
DISCUSSION