Lithotripsy

Kidney stones are formed from deposits of salt and mineral crystals on the inner surface of the kidneys or in the bladder. Often this occurs when the urine is persistently either acidic or alkaline. Most kidney stones contain large amounts of calcium. They vary in size and may remain inside the kidney or dislodge and pass into the ureter, the tube that carries urine from the kidney to the bladder.

If stones remain inside the kidney they may cause damage directly, or obstruct the flow of urine. Such an obstruction causes a buildup of pressure inside the kidney and interferes with the function of this organ, a condition called hydronephrosis. In turn, this can cause bacterial buildup in the stagnant urine, a condition called acute bacterial pyelonephritis.

Most kidney stones produce no symptoms and are only discovered during a routine x-ray examination, although some stones may cause blood in the urine. Usually, however, people discover they have kidney stones when they are stricken with terrible pain along their side or back, which occurs when the stone moves down the ureter.

A lithotripter directs sound waves at the kidney stones of a patient, causing the stones to break and dissolve. S.I.U., National Audubon Society Collection/Photo Researchers, Inc. Reproduced by permission.

Formerly, the two major forms of treatment were to wait for stones to pass through the bladder in the urine, or to remove it, usually by major abdominal surgery. Later, endoscopes—long light tubes used for looking inside the body—were used to locate stones, which were then grasped or crushed with basketlike devices on the end of tubes inserted under the guidance of endoscopes. But stone formation often recurs, and repeated surgery greatly increases the risk of permanent kidney damage or loss of the kidney. More recently, ESWL has become the common method of treating kidney stones.