Every year, more than half a million Americans visit the emergency room for kidney stone problems.
In most cases, the stones eventually pass out of the body on their own, but the process can be very painful.
In a new study, researchers have developed a new treatment that could make passing kidney stones faster and less painful.
They have identified a combination of two drugs that relax the walls of the ureter—the tube that connects the kidneys to the bladder—and can be delivered directly to the ureter with a catheter-like instrument.
Relaxing the ureter could help stones move through the tube more easily.
The two drugs include nifedipine, a calcium channel blocker used to treat high blood pressure, and a type of drug known as a ROCK (rho kinase) inhibitor, which is used to treat glaucoma.
The research was conducted by a team at MIT and Massachusetts General Hospital.
Kidney stones are made from hard crystals that accumulate in the kidneys when there is too much solid waste in the urine and not enough liquid to wash it out.
It is estimated that about one in 10 people will have a kidney stone at some point in their lives.
While some larger stones require surgery, the usual treatment plan is simply to wait for the stones to pass, which takes an average of 10 days.
Patients are given painkillers as well as an oral medication that is meant to help relax the ureter, but studies have offered conflicting evidence on whether this drug actually helps.
In the study, the team thought that delivering a muscle relaxant directly to the ureter might offer a better alternative.
Most of the pain from passing a kidney stone arises from cramps and inflammation in the ureter as the stones pass through the narrow tube, so relaxing the muscles surrounding the tube could help ease this passage.
The researchers identified two drugs that might work well when delivered directly to the ureter.
The drugs worked even better when given together.
One of these is nifedipine, a calcium channel blocker used to treat high blood pressure, and the other is a type of drug known as a ROCK (rho kinase) inhibitor, which is used to treat glaucoma.
According to the team, this kind of treatment could also make it easier and less painful to insert stents into the ureter, which is sometimes done after a kidney stone is passed, to prevent the tube from becoming blocked or collapsing.
They believe this could significantly impact kidney stone disease, which affects millions of people.
More studies are needed to determine how long the muscle relaxing effect lasts and how much relaxation would be needed to expedite stone passage.
The lead author of the study is Michael Cima, the David H. Koch Professor of Engineering in MIT’s Department of Materials Science and Engineering.
The study is published in Nature Biomedical Engineering.
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