Irritable bowel syndrome (IBS) is a common functional bowel disorder characterised by symptoms of recurrent abdominal pain associated with a change in bowel habit. This condition is one of the most frequent reasons to seek a gastroenterology consultation in primary and secondary care. The diagnosis of IBS is made by identifying characteristic symptoms, as defined by the Rome criteria, and excluding organic gastrointestinal diseases that might otherwise explain these symptoms. Organic conditions that can be mistaken for IBS include coeliac disease, inflammatory bowel disease (IBD), colorectal cancer, and, in those with diarrhoea-predominant symptoms, chronic gastrointestinal infections, microscopic colitis, and primary bile acid diarrhoea. The concept of small intestinal bacterial overgrowth being associated with IBS is shrouded with controversy and uncertainty, mainly because of invalid tests due to poor sensitivity and specificity, potentially leading to incorrect assumptions. There is insufficient evidence to link IBS-type symptoms with exocrine pancreatic insufficiency or with symptomatic uncomplicated diverticular disease, since both are hampered by conflicting data. Finally, there is growing appreciation that IBS can present in patients with known but stable organic gastrointestinal diseases, such as quiescent IBD or coeliac disease. Recognising functional gut symptoms in these individuals is paramount so that potentially harmful escalations in immunosuppressive therapy can be avoided and attention can be focused on addressing disorders of gut–brain interaction. This Review endeavours to aid clinicians who practise adult gastroenterology in recognising the potential overlap between IBS and organic gastrointestinal diseases and highlights areas in need of further research and clarity.

肠易激综合症（IBS）是一种常见的功能性肠病，其特征是与习惯改变相关的反复腹痛症状。这种情况是在初级和二级保健中寻求肠胃科咨询的最常见原因之一。IBS的诊断是通过识别罗马标准定义的特征性症状，并排除可能解释这些症状的器质性胃肠疾病。可以误认为IBS的器质性疾病包括腹腔疾病，炎性肠病（IBD），结肠直肠癌，以及那些以腹泻为主的症状的慢性胃肠道感染，微观结肠炎和原发性胆汁酸腹泻。与IBS相关的小肠细菌过度生长的概念充满争议和不确定性，这主要是由于敏感性和特异性较差而导致的无效测试，可能导致错误的假设。没有足够的证据将IBS型症状与外分泌性胰腺功能不全或有症状的单纯性憩室病联系起来，因为两者都受到冲突数据的阻碍。最后，人们越来越认识到，IBS可以存在于已知但稳定的器质性胃肠道疾病中，例如静态IBD或腹腔疾病。在这些个体中认识到功能性肠道症状至关重要，因此可以避免免疫抑制治疗中潜在的有害升级，并且可以将注意力集中在解决肠道-大脑相互作用的疾病上。