Unmasking Amoebiasis: An Unexpected Cause of Colitis in a Non-endemic Region

Amoebic colitis is a common mimic of inflammatory bowel disease (IBD), primarily encountered in developing countries. We present a case of a 73-year-old British male with no travel history to any amoebic endemic regions, who presented with a three-month history of per rectal (PR) bleeding, diarrhoea, and a positive faecal immunochemical test (FIT). Prior to this, he reported no history of experiencing any gastrointestinal symptoms. Colonoscopy revealed patchy pan-colitis, most marked in the ascending colon, and histology confirmed chronic inflammation. A diagnosis of IBD was made, and the patient was started on corticosteroids and 5-aminosalicylates (5-ASA). He subsequently presented to the emergency department (ED) with worsening symptoms and rising inflammatory markers. Flexible sigmoidoscopy showed progression of inflammation, and despite treatment with intravenous corticosteroids and infliximab, a tumour necrosis factor-alpha (TNF-α) inhibitor, there was no improvement. Cross-sectional imaging performed due to new-onset breathlessness during this admission identified multiple hepatic abscesses and a superior mesenteric vein thrombus. Immunosuppression was stopped, and broad-spectrum antibiotics were initiated. Liver biopsy showed inflammatory cells, but no microorganisms were seen on cultures. Due to treatment-refractory colitis and contraindications to further immunosuppression, the patient underwent a laparoscopic subtotal colectomy with end ileostomy. Histology of the resected bowel was not in keeping with IBD, prompting re-evaluation of the initial biopsies taken from the colonoscopy at first presentation. On re-examination, amoebic-like trophozoites were seen, and the diagnosis of amoebic colitis was confirmed following review by a tertiary centre for specialist infectious disease and gastrointestinal pathology. This case highlights the need for a broad differential when managing treatment-refractory colitis, particularly in non-endemic regions, where the index of suspicion for amoebic colitis is low, and the risk of misdiagnosis is high.