Kidney stones are a recurring and nightmare faced by millions of Americans. Every year, more than 500,000 Americans are taken to hospitals for painful kidney stone problems.

Also called urolithiasis, kidney stone disease occurs when a solid kidney stone develops in the urinary tract. Kidney stones are consist of hard crystals that accumulate in the kidneys when there is too much solid waste in urine and not enough liquid to wash it out.

If the stone is large, or more than 5 millimeters (0.2 inches) in diameter, it can block the ureter, causing severe pain in the lower back or abdomen. The ureter is the tube that connects the kidneys to the bladder.

A procedure called percutaneous nephrolithotomy surgically removes large kidney stones using small telescopes and instruments inserted through a small incision in the patient's back. Most small kidney stones won't require invasive treatment. A person might be able to pass a small stone by drinking water and by taking pain relievers or alpha blockers.

The usual treatment plan is simply to wait for the stones to pass. This takes an average of 10 days, and patients are given painkillers and an alpha blocker to help relax the ureter. Studies, however, reveal conflicting evidence on whether alpha blockers actually help. Note that there are no FDA-approved oral therapies for kidney stones and ureteral dilation.

Researchers at MIT and Massachusetts General Hospital (MGH) recently devised a potential treatment that might make passing kidney stones faster and less painful. Both institutions have identified a combination of two drugs that relax the walls of the ureter and can be delivered directly to the ureter with a catheter-like instrument. In a recently published study, researchers said relaxing the ureter might help kidney stones move through the ureter more easily.

"We think this could significantly impact kidney stone disease, which affects millions of people," Dr. Michael Cima, senior author of the study and the David H. Koch Professor of Engineering in MIT's Department of Materials Science and Engineering, said.

Dr. Christopher Lee, a recent Ph.D. recipient in the Harvard-MIT Division of Health Sciences and Technology, is the lead author of the study, which was published in ther journal Nature Biomedical Engineering.

This kind of treatment might also make it easier and less painful to insert stents into the ureter. This procedure is sometimes done after a kidney stone is passed to prevent the tube from becoming blocked or collapsing.

Cima and Brian Eisner, who co-directs the Kidney Stone Program at MGH, thought delivering a muscle relaxant directly to the ureter might be a better alternative. They noted 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. This observation suggests relaxing the muscles surrounding the tube might help ease this passage.

They tested 18 drugs to measure how much the drugs relaxed the smooth muscle cells. They also used intensive computational processing to individually analyze the relaxation responses of nearly one billion cells after drug exposure.

They later identified two drugs that worked quite well and found they worked even better when given together. One of these is nifedipine, which is a calcium channel blocker used to treat high blood pressure. The other is a type of drug known as a ROCK (rho kinase) inhibitor, which is used to treat glaucoma.

Researchers said more studies are needed to determine how long the muscle relaxing effect lasts and how much relaxation will be needed to expedite stone passage. They're now launching a startup company, called Fluidity Medicine, to continue developing the technology for testing in human patients.

Kidney Stone
Sex can help with passing painful kidney stones. dfaulder, CC by 2.0