Parasitic colitis misdiagnosis as inflammatory bowel disease in high-income settings and association with poor clinical outcomes when exposed to corticosteroids: a systematic review of case reports.

OBJECTIVES: Parasitic colitis is highly prevalent worldwide, may mimic inflammatory bowel disease (IBD) and is encountered by non-specialist physicians in high-income, non-endemic settings. In this context, patients may be at risk of misdiagnosis and poor outcomes. However, cases are not routinely reported, limiting the evidence base to individual case reports. We aimed to systematically describe and evaluate the diagnosis, clinical course and outcomes of affected patients whose cases have been reported in high-income settings. DESIGN: A systematic review of the literature using the Preferred Reporting Items for Systematic Reviews and Meta-analyses framework. DATA SOURCES: PubMed and Scopus databases were searched for publications from between 1 January 2012 and 10 January 2025. ELIGIBILITY CRITERIA: Case reports of undifferentiated colitis presenting in high-income settings, where the aetiological agent was ultimately found to be parasitological, were eligible for inclusion. Key exclusion criteria included a history of travel to an endemic area within 4 weeks of presentation. No language restrictions were applied. DATA EXTRACTION AND SYNTHESIS: Key components of each case report, encompassing patient presentation, diagnosis and management, were standardised as categorical descriptors. Key themes were identified, and a thematic synthesis approach was employed. RESULTS: 52 articles, describing 54 patients, were included in the final analysis: 33 cases of amoebiasis, 15 cases of strongyloidiasis and 6 cases of schistosomiasis. Misdiagnosis occurred in 37 out of 54 patients (69%), with 28 out of 37 (76%) of these misdiagnosed as IBD. Substantial harm was reported in 31 out of 54 (57%) patients, including death in seven patients. Major morbidity (defined as strongyloides hyperinfection syndrome, fulminant amoebic colitis, emergency surgery or sepsis) or death was associated with administration of corticosteroids in cases of strongyloidiasis and amoebiasis, occurring in 8 out of 9 (89%) and 1 out of 6 (17%) patients with strongyloidiasis who received/did not receive corticosteroids, and 10 out of 13 (77%) and 2 out of 20 (10%) patients with amoebiasis, respectively. CONCLUSIONS: Parasitic colitis poses a diagnostic challenge in high-income settings. Misdiagnosis as IBD is commonly reported, with poor outcomes related to corticosteroid treatment. Awareness of parasitic colitis aetiologies, at-risk groups and diagnostic tests is essential among generalist clinicians assessing undifferentiated colitis to avoid poor outcomes. PROSPERO REGISTRATION NUMBER: CRD420251033374.