Magnetically actuated microrobots in urolithiasis: emerging frontiers in kidney stone diagnosis and management

Urolithiasis is a common and recurrent urinary tract disorder in which stone size, composition, location, anatomy, and patient factors influence the choice and success of treatment. Although shock wave lithotripsy (SWL), ureteroscopy (URS), and percutaneous nephrolithotomy (PCNL) provide effective treatment for many patients, residual fragments, difficult calyceal access, repeated procedures, tissue trauma, and procedure-specific risks remain relevant clinical challenges. These limitations have encouraged investigation of miniature, wirelessly controlled systems that could reach confined regions of the urinary tract and perform localized diagnostic or therapeutic tasks. This review examines magnetically actuated microrobots and related magnetic microdevices for kidney stone navigation, detection, fragmentation, dissolution, and fragment retrieval. Particular attention is given to rotational, oscillatory, and gradient-driven actuation; magnetic materials and biocompatible coatings; integration with ultrasound, magnetic resonance imaging, and other sensing approaches; and hybrid magnetic-acoustic or drug-delivery platforms. Rather than treating all microrobotic studies as equivalent, the review distinguishes direct urolithiasis evidence from evidence transferred from other biomedical applications. The available evidence remains predominantly preclinical. Demonstrations include urinary-tract phantoms, microfluidic models, ex vivo experiments, and selected animal studies, while human clinical trials of magnetically actuated microrobots for kidney stone diagnosis or treatment have not been established in the literature reviewed here. Accordingly, the principal value of these systems at present is technological feasibility rather than demonstrated clinical superiority. Key barriers include real-time localization, magnetic-force attenuation with depth, safe deployment and retrieval, obstruction or urothelial injury, material fate, manufacturing reproducibility, regulatory classification, and cost-effectiveness. Future clinical claims should therefore be considered prospective and conditional on rigorous validation.