Which flexible ureteroscope is the best for upper tract urothelial carcinoma treatment?

To present attributes of currently available flexible ureteroscopes to define the best flexible ureteroscope for upper tract urothelial carcinoma (UTUC) treatment. Scopus and Medline databases were searched for articles relating to performance of flexible ureteroscopes. A consensus for final inclusion of articles judged to be relevant for UTUC treatment was reached between the authors. Instrument characteristics were extracted from manufacturers' product brochures. Smaller cross-sectional size of instruments is associated with increased probability for successful primary access to the upper urinary tract. The smallest flexible ureteroscopes are fiberoptic scopes. Smaller ureteroscopes also allow comparatively increased irrigation flow at constant intrarenal pressure. Digital flexible ureteroscopes achieve superior image quality compared to their fiberoptic counterparts, at the price of lower end-deflection ability. Image enhancement technologies such as narrow-band imaging (NBI), photodynamic diagnosis (PDD) and Image 1-S (formerly SPIES) are based on subjective image interpretation by the operator. NBI and PDD significantly increase tumor detection rate. The highest subjective image quality score of the Image 1-S technology is reached by the "Clara + Chroma" mode. Single-use ureteroscopes offer potential advantages over reusable scopes, including sterility, absence of contamination, immediate availability and exemption of previous instrument wear. Miniaturization, digital image caption and image enhancement technologies seem to be the major determinants defining the best flexible ureteroscope for UTUC treatment. The impact of further factors, such as distal tip design, torque, working channel position, risk of contamination, as well as upcoming technological innovations should be evaluated in randomized controlled trials.