Removing Kidney Stones Without Anesthesia

Passing kidney stones through urine is a painful condition that people who have experienced it once would never wish to repeat. For those uninitiated about this disease, kidney stones are hard deposits of minerals and acid salts that stick together in concentrated urine.

Though it causes severe pain when passing through the urinary tract, kidney stones usually do not cause permanent damage.Treatments include pain relievers and drinking lots of water to help pass the stone. Medical procedures, such as ultrasound technologies administered while under anesthesia, may also be required to remove or break up larger stones.

A new technique which combines the use of two ultrasound technologies may offer an option to move kidney stones out of the ureter with minimal pain and no anesthesia. In this procedure, the physician uses a handheld transducer placed on the skin to direct ultrasound waves towards the stone. A transducer is a device that converts changes in electric signal into a physical quantity, such as sound, pressure or brightness, and vice versa.

In this case, the ultrasound produced by the transducer is used to move and reposition the stones to promote their passage through the urinary tract, a process called ultrasound propulsion, or to break up the stone, a technique called burst wave lithotripsy (BWL).

Unlike shock wave lithotripsy, which is the standard procedure now in use and requires sedation, this technology does not cause any pain. The research team hopes that, with this new technology, the procedure of moving or breaking up the stones could eventually be performed in a clinic or emergency room setting.

Stones in the ureter, the passage which leads from the kidney to the bladder, can cause severe pain and are a common reason for emergency department visits. Most patients with ureteral stones are advised to wait to see if the stone will pass on its own. However, this observation period can last for weeks and can be a painful time for the patient, with nearly one-fourth of patients eventually requiring surgery. Up to 50 percent of patients with a stone event will probably have a recurrence within five years.

The research into developing a technology to remove kidney stones under emergency situations in a non-medical environment, first started several years ago, when the US space agency NASA funded a study to see if kidney stones could be moved or broken up, without anesthesia, on long space flights.

Scientists at the University of Washington and at the university’s Northwest Kidney Stone Center, behind the new study, also focused on making the removal of kidney stones painless and without the use of anesthesia, so that eventually it could become a routine clinical procedure. Meanwhile, other medical trials at the university have concentrated on breaking apart kidney stones inside the kidneys.

This new trial is the first to look at moving the stones or breaking them apart in the ureter with BWL mentioned earlier. For their study, the researchers recruited 29 patients, of whom 16 were treated with propulsion alone and 13 with propulsion and burst wave lithotripsy. In 19 patients, the stones moved. In two cases, the stones moved out of the ureter and into the bladder.

The study noted that burst wave lithotripsy fragmented the stones in seven of the cases. At a two-week follow up, 18 of 21 patients (86%) whose stones were located lower in the ureter, closer to the bladder, had passed their stones. In this group, the average time to stone passage was about four days.

The researchers said their next step would be to perform a clinical trial with a control group, which would not receive either BWL bursts or ultrasound propulsion, to evaluate the degree to which this new technology potentially aids stone passage.