Stanford’s Magnetic Device Revolutionizes Kidney Stone Retrieval

Stanford University has developed a groundbreaking ureteroscopy-compatible device that utilizes magnetism to retrieve kidney stone fragments more effectively than traditional methods. This innovative approach demonstrated superior performance in a preclinical study conducted on pigs, addressing a significant medical challenge faced by approximately 11% of the U.S. population who suffer from kidney stone disease.

Current treatment for kidney stones often involves ureteroscopic laser lithotripsy, a procedure that fragments stones using laser technology. However, the removal of these fragments remains inefficient, with residual pieces remaining in up to 40% of patients. These leftover fragments can cause complications such as pain, infections, and the need for additional surgical interventions.

The device developed at Stanford aims to improve this situation. Stones form from crystallized salts, obstructing the ureters that transport urine from the kidneys to the bladder. This obstruction can lead to severe pain, infections, and potential kidney damage. The standard procedure, while effective, leaves many patients with leftover stones that could result in further health issues. Statistics indicate that 30% of patients with residual fragments require another operation within five years, contrasted with just 4% for those without.

The economic burden of kidney stones is substantial. In the U.S. alone, there are more than 1.3 million emergency visits linked to kidney stones, leading to annual healthcare costs exceeding $4 billion. Projections suggest that this number could increase by an additional $1.2 billion annually by 2030, fueled by rising obesity and diabetes rates, which are significant risk factors for stone formation.

In the study titled “Magnetic retrieval of kidney stones via ureteroscopy in a porcine model,” published in the journal Device, researchers engineered a system that magnetizes stone fragments using a hydrogel. This system allows for retrieval with a magnetic wire under direct endoscopic visualization in pigs. The experimental setup mirrored clinical ureteroscopy instruments, employing a 3D-printed kidney model submerged in a saline bath to simulate conditions within a living organism.

The researchers positioned human-derived kidney stone fragments within the model and utilized two hydrogel precursors—ferumoxytol and chitosan. These were co-delivered through a dual-lumen injector, allowing the hydrogel to form on the fragment surface. The magnetic wire was then used to attempt retrieval. Control kidneys were subjected to standard fragment placement and basket retrieval only.

Results from the study showed promising outcomes. During one-week survival experiments, pigs displayed normal urination and uneventful recovery, with urinalysis and blood tests remaining within normal ranges. Traditional irrigation methods managed to clear about 70% of the hydrogel used during the procedures. However, the combination of magnetic retrieval and irrigation resulted in the clearance of 99.8% of the gel within just ten minutes.

Future research aims to refine this magnetize-and-retrieve strategy further. The authors of the study concluded that their method is feasible and compatible with clinical ureteroscopes, exhibiting a favorable short-term safety profile. Plans include head-to-head testing in a ureteroscopy model, enhancements to hydrogel formulations for simplified dosing, improvements in catheter technology, and exploration of alternative magnetic geometries.

The successful translation of this method into a clinical setting has the potential to increase stone-free elimination rates, reduce adverse patient outcomes, and alleviate healthcare burdens associated with kidney stone disease. This innovative approach represents a significant advancement in urological procedures, potentially transforming how kidney stones are managed in the future.