A researcher reports preliminary success in using electrically generated shock waves to crush painful and often dangerous gallstones lodged in the bile duct that cannot be removed surgically.

The technique, used since the early 1980s to smash kidney stones, has been approved by the Food and Drug Administration for testing on stones wedged in the narrow duct that connects the gallbladder to the liver and the small intestine. European and Canadian doctors have successfully used the method on 60 such patients in the past two years.

Some 4 percent to 15 percent of the 500,000 Americans who undergo gallbladder operations each year also have stones lodged in the bile duct. Left undetected, the stones produce such symptoms as pain, jaundice or even life-threatening infections in the majority of patients within five years.