FANS – How it works, how best to use it and implications for stone treatment

Introduction: Conventional flexible ureteroscopy (fURS) techniques are limited by residual fragments, infectious complications and stone size. Flexible and Navigable Suction Ureteral Access Sheaths (FANS) have been developed to address these limitations through controlled suction and pressure modulation within the pelvico-calyceal system (PCS). Methods: This narrative review summarises the design principles of FANS, outlines practical considerations for their use, and synthesises evidence on their use. Results: FANS incorporate a flexible distal tip permitting advancement into the PCS. By bypassing the pelvico-ureteric-junction (PUJ), FANS establish a low-resistance outflow, lowering IRP and increasing effective irrigation flow. Higher flow rates and continuous evacuation of stone dust may improve endoscopic visibility and enhance heat dissipation. Clinical studies demonstrate higher stone-free rates and lower infectious complications compared with conventional fURS. Non-inferior stone-free rates have been reported compared with mini-percutaneous nephrolithotomy for high stone burdens, with lower major complications. Their optimal use requires understanding the interaction between sheath and scope size, irrigation and suction pressure to avoid PCS collapse or over-pressurisation. Conclusions: FANS represent a potential paradigm shift in RIRS with improved SFRs and reduced infectious complications. Long-term data are required to quantify the risk of PUJ strictures and to quantify cost-effectiveness and clinical benefits, especially in larger stone burdens. Level of evidence: 5