New medical techniques have, in the past decade, made major surgery for kidney stones all but obsolete, The Western Journal of Medicine reports.

Almost a third of stones can be dissolved by drinking large amounts of water and alkali, Dr. George W. Drach of Tucson writes. Drugs and diet limitations -- cutting back on calcium, for example -- can prevent the formation of many new stones.

And of those stones that can't be dissolved with drugs, only about 20 percent "will require 'big' operations," the journal reports. Most can be pulverized with new ultrasound techniques, including one -- lithotripsy -- that requires no incision at all.

The result: Stone recurrence rate has been cut from 80 percent to 20 percent, the average hospital stay has been cut from eight days to four, and the average time lost from work has been cut from six weeks to 10 days.

In related research, scientists think they have figured out why men account for 80 percent of calcium oxalate kidney stones, the only kind that can't be treated with medication.

Women have higher levels of citrate, a natural stone inhibitor, two University of Chicago researchers say. Another stone inhibitor, a protein called urinary glycoprotein crystal growth inhibitor, is often lacking in men.

"The drug potassium citrate may be given to increase citrate levels" and block stone formation, says researcher Joan Parks, "although its long-term effects are not known."