Magnetic gel can remove kidney stones more effectively

The magnetic device may be able to remove kidney stones more efficiently than standard methods, avoiding the need for repeated surgical procedures.

Kidney stones occur when minerals in the urine crystallize. It can be painful when it lodges inside the kidney or enters the ureters, which are the tubes that connect the kidneys to the bladder.

It is often treated by breaking it into smaller pieces. This may involve pushing a thin tube with a lithotripsy laser at the end through the bladder into the ureter and kidney, or pulsing ultrasound waves from outside the body.

Surgeons can then remove the stone fragments, usually one at a time, using a wire basket that is fed in and out of the urethra. But this frequent retrieval can cause tissue damage. In about 40% of cases, splinters are left behind, partly because particularly small splinters slip through the basket. These carry the risk of forming more stones.

In search of an alternative approach, Joseph Liao He and his colleagues at Stanford University in California developed a magnetic gel, which covers kidney stone fragments, and a magnetic wire, which they used to capture the fragments in a laboratory dish.

Now, they have tested this approach on four pigs. They inserted dozens of fragments of human kidney stones into the animals’ kidneys before injecting the organs with magnetic gel. Using a magnetic wire inserted through the urethra, they were able to retrieve multiple stone fragments at once, rather than just one piece at a time, as is usually the case with the wire basket method. “It’s like using a stick to fish out mucus full of stone chips, so you can remove a large amount of it in one go,” Liao says.

This suggests that this technique will cause less tissue damage than the standard method, as surgeons will need to go in and out of the kidneys less often. It can also remove splinters from the kidney completely, Liao says, because, unlike wire baskets, the magnetic device can pick up pieces of any size. This reduces the risk of new stones forming and the need for further surgery.

“It’s a very promising approach,” he says. Veronica Magdanz at the University of Waterloo in Canada, who was not involved in the study. “Anything that increases the success of collecting stones and captures more pieces at a time is beneficial.”

There were no side effects on any of the pigs due to the gel. “It’s very good news; it’s not toxic or harmful in any way,” Magdanz says. After refining this approach in further pig studies, the team hopes to try it in humans within about a year, Liao says.

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