Lithotriptor therapy coming of age.

Lithotriptor therapy coming of age

For the past two years, researchers have been experimenting with extracorporeal shock wave lithotripsy as a means of breaking up gallstones. The nonsurgical technique--which uses high-pressure shock waves to dissolve mineral deposits-- has proved extremely effective against kidney stones (SN: 9/6/87, p.157), but early results with gallstones were only moderately encouraging (SN: 4/26/86, p.265). Recent research using a new model of lithotriptor has been more successful, however, and the Food and Drug Administration (FDA) recently announced it will sponsor U.S. clinical trials of gallstone lithotripsy beginning this fall.

The new research was reported at a recent series of digestive-disease meetings in Chicago and is discussed in the Sept. 11 JOURNAL OF THE AMERICAN MEDICAL ASSOCIATION.

Using a modified version of the $1.5 million lithotriptor already being used to break up kidney stones, researchers in West Germany have recorded a greater than 80 percent success rate in breaking up stones in the gall bladder and bile duct. The new device differs from the original kidney lithotriptor in that it uses ultrasound rather than X-rays to locate the stones. Kidney stones, which are made largely of calcium, show up well with X-rays. But gallstones, which are usually made of cholesterol, are more easily visualized with ultrasound.

Another innovation in the gallstone lithotriptor--and an improvement being incorporated into newer versions of the kidney lithotriptor as well--has the patient resting on a cushion filled with 25 gallons of water. (The original model required that the patient be immersed in a tank of water.) A layer of ultrasound gel between patient and cushion ensures minimal loss of energy as the shock waves are generated by spark discharge in the water-filled cushion. The newer system also boasts a computer-controlled guidance system that more accurately aims the shock waves at the stones.

Short of surgery, the only gallstone therapy currently approved in the United States is treatment with chenodeoxycholic acid. When used over a period of many months, the acid is able to dissolve some types of gallstones. In many cases, however, gallstone sufferers have no choice but to undergo cholecysectomy, or removal of the gall bladder.

More than 400,000 Americans undergo gallstone surgery each year--nearly four times the number of surgeries performed annually for kidney stones. The operation typically involves a six- to eight-day hospital stay and a four- to six-week recovery period.

In contrast, gall bladder lithotripsy requires a two- to three-day hospitalization, and that may decrease before too long. Physicians who are familiar with the technique are predicting that it will become available as an outpatient procedure. Such optimism is strengthened by recent reports that mild sedatives --rather than general anesthesia--are sufficient to keep the procedure painless.

In one such study, appearing in the September ANNALS OF INTERNAL MEDICINE, intravenous analgesics were given to 10 patients who underwent gallstone lithotripsy. Gustav Paumgartner and his colleagues at the University of Munich, West Germany, found that pain was not a problem in any of the cases. Moreover, they found, the procedure was made easier because the patients were conscious and were able to position themselves on the water-filled cushion.

In the United States, 10 hospitals have been selected by the FDA to participate in clinical testing of the new gallstone lithotriptor. Physicians from those hospitals are now in Munich being trained to use the new machine. The U.S. trials, which are expected to run until the end of next year, will look at the safety and efficacy of the procedure as performed on 600 carefully selected patients.