Magnetic Kidney Stone Retrieval Device Outperforms Ureteroscopic Laser Lithotripsy

Kidney stone disease affects millions worldwide and often requires ureteroscopic laser lithotripsy, yet fragment removal remains inefficient. Many patients are left with residual pieces that can cause pain, infection, and repeat procedures, creating a long-term clinical and financial burden. These fragments persist in up to 40% of cases, with a significant proportion requiring another operation within five years. To address this challenge, researchers have developed and tested a new solution to improve fragment retrieval during minimally invasive procedures.

The solution was developed by Stanford University School of Medicine (Stanford, CA, USA), which engineered a ureteroscopy-compatible system designed to magnetize and capture stone fragments. The device uses a dual-lumen injector to coat fragments with an in situ–forming magnetic hydrogel composed of ferumoxytol and chitosan. A magnetic wire then retrieves the labeled pieces under direct endoscopic visualization.

Benchtop studies used a 3D-printed kidney model submerged in saline, where human-derived calcium oxalate fragments were positioned for testing. The researchers reported that adding glycerol to the chitosan precursor solved a density mismatch and improved magnetic labeling of 1–2 mm fragments fourfold. Ureteroscopy runs demonstrated successful removal of multiple fragments after a single hydrogel application, with 28 pieces extracted in six passes. Pig studies showed an uneventful one-week recovery, normal urination, and normal laboratory values. Combined irrigation and magnetic retrieval cleared 99.8% of the hydrogel within 10 minutes, and imaging confirmed no detectable residues after one week.

The findings, published in Device, demonstrate that a magnetize-and-retrieve approach is feasible, compatible with clinical ureteroscopes, and shows a favorable short-term safety profile. The strategy could increase stone-free rates, lower repeat procedures, and help reduce the growing healthcare burden driven by rising obesity and diabetes. Researchers plan to refine the hydrogel formulation, improve catheter design, compare performance against current extraction tools, and explore new magnetic geometries to support future clinical translation.

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Stanford University School of Medicine