Kidney stones result from the precipitation (crystallization of previously dissolved particles) of
certain substances within the urine. These stones form in the kidney and subsequently
travel through the ureter (the tube that conducts
urine from the kidney to the bladder) and are eliminated through the urine
if they are small. In some cases, the stone may not be able to travel through
the ureter, causing pain and possibly causing an obstruction, blocking the
flow of urine out of the kidney. Kidney stones can be caused by a large number
of factors, such as infection, certain diets, medications, and conditions
that result in an increased concentration of calcium or other substances,
including oxalate and uric acid, in the urine. The composition of the stone
depends on the cause, but the most common type of stone contains calcium.
The March 2, 2005, issue of JAMA includes an article
that reviews the causes and diagnosis of kidney stones and the available treatments.