Stanford Device Uses Magnetism to Improve Kidney Stone Removal

Stanford University has developed a groundbreaking ureteroscopy-compatible device designed to enhance the retrieval of kidney stone fragments using magnetism. In preclinical trials conducted on pigs, the device demonstrated superior performance compared to traditional removal methods. This innovation could significantly improve patient outcomes for the approximately 11% of the population affected by kidney stone disease.

Kidney stones form from crystallized salts, obstructing the urinary tract and causing severe pain, infections, and potential kidney damage. The most common treatment is ureteroscopic laser lithotripsy, where a laser breaks stones into smaller pieces that can be removed or passed naturally. Yet, residual fragments remain in up to 40% of patients, often leading to complications such as emergency visits and repeat procedures.

The financial implications are considerable, with more than 1.3 million emergency visits related to kidney stones in the United States, contributing to over $4 billion in annual healthcare costs. Projections suggest that rising rates of obesity and diabetes—significant risk factors for stone formation—could add an additional $1.2 billion in healthcare expenditures by 2030.

Magnetic retrieval of kidney stones via ureteroscopy in a porcine model, published in the journal Device in March 2025, outlines the creation of a system that uses a hydrogel to magnetize stone fragments and a magnetic wire for retrieval. This approach was tested under conditions that closely mirrored clinical ureteroscopy techniques.

The research involved a 3D-printed kidney model submerged in a saline bath, where human-derived kidney stone fragments were placed. Using a dual-lumen injector, researchers co-delivered two hydrogel precursors—ferumoxytol and chitosan—to form a magnetic hydrogel that adhered to the stone fragments. In trials, pig kidneys received the retrograde placement of fragments, followed by hydrogel application and retrieval attempts with the magnetic wire.

Initial results revealed a density mismatch between the two hydrogel components, which was corrected by adding glycerol to increase magnetic labeling effectiveness. The results were promising; a total of 28 fragments sized between 1 and 2 mm were successfully removed in just six retrieval attempts after the hydrogel was applied.

In one-week survival trials, pigs showed normal urinary function post-procedure, with urinalysis and blood tests indicating no adverse effects. Notably, the combination of magnetic retrieval and irrigation cleared 99.8% of the hydrogel within ten minutes, demonstrating the effectiveness of this new method.

The researchers concluded that their magnetize-and-retrieve strategy is not only feasible but also compatible with existing clinical ureteroscopes, showing a favorable safety profile for short-term use. Future research will focus on head-to-head comparisons in ureteroscopy models, refining hydrogel formulations, and exploring alternative magnetic geometries.

Successful implementation of this technology could drastically improve stone-free elimination rates, ultimately reducing the risk of complications and the healthcare burden associated with kidney stones.