Optical Spectroscopy and Spectral Imaging for Bladder Cancer Detection and Characterisation: A Scoping Review of Diagnostic Evidence and Translational Readiness

Background/Objectives: White-light cystoscopy remains central to bladder cancer detection and surveillance, but diagnostic uncertainty persists in detecting flat lesions, particularly carcinoma in situ, distinguishing inflammatory mimics, and targeting biopsies. Optical spectroscopy and spectral imaging may provide objective tissue information beyond visual inspection. This scoping review mapped the diagnostic evidence and translational readiness of these technologies. Methods: A scoping review was performed in accordance with the Preferred Reporting Items for Systematic Reviews and Meta-Analyses extension for Scoping Reviews (PRISMA-ScR). PubMed, Embase and Web of Science were searched from inception to 31 July 2026. Eligible articles evaluated wavelength-dependent optical signals directly in human bladder tissue in clinically relevant in vivo or ex vivo settings. Related articles with the same, overlapping or expanded datasets were grouped into study families. Results: Forty-seven articles were organised into 39 study families. Raman spectroscopy showed the clearest progression from ex vivo discrimination to in vivo cystoscopic feasibility and device development. Fluorescence and reflectance provided early in vivo evidence, although specificity was often limited by inflammation and benign changes. Infrared and near-infrared techniques remained mainly specimen-based, while multimodal systems were evaluated mostly ex vivo. Evidence for spectral imaging was limited, and no clinically integrated endoscopic hyperspectral-imaging study meeting the criteria was identified. Conclusions: Optical spectroscopy and spectral imaging show diagnostic potential for bladder cancer tissue characterisation, but evidence remains heterogeneous and insufficient for routine implementation. Among the included techniques, Raman spectroscopy appears most translationally mature, whereas wide-field spectral imaging remains underdeveloped. Future studies should prioritise prospective in vivo evaluation, standardised acquisition, histopathological correlation, external patient-level validation and clinically meaningful endpoints.