Circulating and faecal microRNAs as non-invasive biomarkers for IBD: current evidence and next steps.

Despite substantial progress in understanding the complex pathophysiology of inflammatory bowel diseases (IBD), specific and accurate non-invasive biomarkers for diagnosis and disease monitoring remain an unmet clinical need. Endoscopy and histology are still considered the diagnostic gold standard, while fecal calprotectin has been increasingly adopted in practice but with recognized limitations. Blood-derived biomarkers, in contrast, remain largely nonspecific and of limited utility. Since the discovery of small non-coding RNAs known as microRNAs, these molecules have emerged as promising candidates for non-invasive diagnosis across a range of diseases, including IBD. Over the past decade, a growing body of research has investigated their potential in blood and fecal samples; however, systematic evaluation and integration of this evidence are still lacking. In this review, we provide a comprehensive synthesis of current studies on circulating and fecal miRNAs as non-invasive biomarkers for IBD, highlighting methodological heterogeneity and outlining key directions for future research toward clinically applicable next-generation biomarkers.