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Another assault on hard rock.

Hard rock music may afflict the hearing of many, but a very different type of hard rock-the kidney stone-afflicts about 350,000 Americans each year. When a kidney stone blocks the ureter (the duct that carries urine from the kidney to the bladder), the result is excruciating pain. When a stone blocks the kidney itself, the result may be the even more devastating loss of the kidney.

Boston's Massachusetts General Hospital has developed, and is now testing, a new machine to break up stones in the ureter. Called the electromechanical impactor (EMI), it works like a tiny jackhammer, according to Dr. Stephen Dretler, the MGH urologist who helped to develop it. A large, needle-like device, enclosing a spring with a metal head, is threaded into the urinary tract until the head touches the stone. Tiny explosions created by an electrical spark repeatedly thrust the head against the stone until it breaks up.

The EMI device was successful in demolishing the stones of 14 of the first 16 patients on whom it was tried. The other two had stones that were simply too hard to break. Because its force is directed only at the stone, it does not injure surrounding tissue. However, because the EMI can only be used for stones in the ureter, the device is still no substitute for laser lithotripsy. Dr. Dretler hopes that refinement of the instrumentation will make it possible for physicians to eventually treat stones in the kidney as well.

In 1984, the Medical Education and Research Foundation was instrumental in bringing to the United States the first lithotripter, a high-tech device from Germany that uses shock waves to break up kidney stones, thus avoiding the necessity of surgical removal. Now found in hospitals throughout the country, the lithotripter has radically changed the treatment of kidney stones. However, its cost-over $1 million-prohibits many smaller hospitals from acquiring it. The EMI, says its manufacturers, costs only about $6,000.

If continued testing on the EMI device is successful, and the FDA approves its use, the machine will be a boon to the thousands of small hospitals around the country that cannot afford a lithotripter. However, hospitals having lithotripters will undoubtedly continue to use them. Lithotripsy uses shock waves generated outside the body to break up the stones and thus avoids the necessity of inserting a tube into the urinary tract, which carries the possibility of infection.
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Title Annotation:kidney stones
Publication:Medical Update
Date:Nov 1, 1991
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