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

## TL;DR

A British man with no travel history was misdiagnosed with IBD but later found to have amoebic colitis, highlighting the need for broader differential diagnosis in non-endemic regions.

## Contribution

This case report emphasizes the diagnostic challenge of amoebic colitis mimicking IBD in non-endemic areas and underscores the importance of re-evaluating biopsies in treatment-refractory cases.

## Key findings

- Amoebic colitis was misdiagnosed as IBD in a non-endemic region due to lack of travel history and atypical presentation.
- Histological re-examination confirmed amoebic colitis after initial IBD diagnosis failed to respond to treatment.
- The case highlights the risk of misdiagnosis and the importance of considering rare infections in treatment-refractory colitis.

## Abstract

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.