Ultra-Efficient Kidney Stone Fragment Removal via Spinner-Induced Synergistic Circulation and Spiral Flow

Abstract

Kidney stones can cause severe pain and complications such as chronic kidney disease or kidney failure. Retrograde intrarenal surgery (RIRS), which uses laser lithotripsy to fragment stones for removal via a ureteroscope, is widely adopted due to its safety and effectiveness. However, conventional fragment removal methods using basketing and vacuum-assisted aspiration are inefficient, as they can capture only 1 to 3 fragments (1--3\,mm in size) per pass, often requiring dozens to hundreds of ureteroscope passes during a single procedure to completely remove the fragments. These limitations lead to prolonged procedures and residual fragments that contribute to high recurrence rates. To address these limitations, we present a novel spinner device that enables ultra-efficient fragment removal through spinning-induced localized suction. The spinner generates a three-dimensional spiral and circulating flow field that dislodges and draws fragments into its cavity even from distances over 20\,mm, eliminating the need to chase fragments. It can capture over 60 fragments (0.5--2\,mm) or over 15 larger fragments (2--3\,mm) in a single pass, significantly improving removal efficiency. In this work, the spinner design is optimized via computational fluid dynamics to maximize suction performance. \textit{In vitro} testing demonstrates near 100\% capture rates for up to 60 fragments in a single operation and superior large-distance capture efficacy compared to vacuum-assisted methods. \textit{Ex vivo} testing of the integrated spinner-ureteroscope system in a porcine kidney confirmed its high performance by capturing 45 fragments in just 4 seconds during a single pass and achieving complete fragment clearance within a few passes.