The urinary microbiome, overactive bladder and bladder pain syndrome/interstitial cystitis - mechanisms, diagnostics and therapeutic opportunities.

Overactive bladder and bladder pain syndrome/interstitial cystitis are prevalent, multifactorial disorders with poorly understood pathophysiology. The discovery of the urinary microbiome has overturned the sterile urine paradigm and created new opportunities for mechanistic and translational research. Increasing evidence suggests that bladder microbial communities are associated with urothelial signalling, immune tone and neural pathways that influence urgency, pain and treatment response. In overactive bladder, Lactobacillus-predominant profiles are associated with lower symptom burden and improved response to pharmacotherapy, whereas Gardnerella-enriched and Pseudomonadota-enriched communities positively correlate with refractory disease. In bladder pain syndrome/interstitial cystitis, microbial alterations are not based on a single pathogenic signature but converge on metabolic and immune dysregulation. Multi-omics studies integrating metagenomics, metabolomics and host immune data are beginning to define functional pathways linking microbial metabolites, epithelial barrier function and nociceptor sensitization. Results from emerging clinical trials suggest that urinary microbiome profiling might enable patient stratification and inform treatment selection, whereas interventions, such as probiotics, oestrogen therapy or dietary modulation, hold potential as adjunctive strategies. Together, these advances position the urinary microbiome as a promising contributor to lower urinary tract health and a potential target for precision urology, although the functional importance and causal role of the low-biomass urinary microbiome in disease remain crucial unresolved questions.