Mistakes in the management of irritable bowel syndrome-diarrhoeal subtype and mimics: a narrative review

Irritable bowel syndrome with diarrhoea (IBS-D) is one of the most frequently encountered disorders of gut-brain interaction, yet its diagnosis remains challenging owing to the substantial symptom overlap with a wide range of conditions. These mimics, most notably microscopic colitis (MC), bile acid diarrhoea (BAD), small intestinal bacterial overgrowth (SIBO), coeliac disease, exocrine pancreatic insufficiency (EPI), endocrine disorders, lactase deficiency, sucrase-isomaltase deficiency, early inflammatory bowel disease (IBD) and functional diarrhoea (FD) can all present with identical clinical features, leading to diagnostic error, delayed treatment, and inappropriate symptom-based management. This narrative review synthesizes literature from 1997 to 2025, incorporating guideline recommendations (ACG, AGA, BSG, ECCO), RCTs, meta-analyses, systematic reviews, and expert consensus statements. This review highlights the most critical mistakes in diagnosing, evaluating, managing, and monitoring IBS-D and its mimics, with lapses in clinical reasoning and guideline adherence most consequential.