A kidney stone is a solid mass made up of tiny crystals. One or
more stones can be in the kidney or ureter at the same time. See
also: Cystinuria Renal calculi; Nephrolithiasis; Stones - kidney
Causes, incidence, and risk factors: Kidney stones can form when
urine contains too much of certain substances. These substances
can create small crystals that become stones. The biggest risk
factor for kidney stones is dehydration. Kidney stones may not
produce symptoms until they begin to move down the tubes
(ureters) through which urine empties into the bladder. When
this happens, the stones can block the flow of urine out of the
kidneys. This causes swelling of the kidney or kidneys, causing
pain. The pain is usually severe. Kidney stones are common. A
person who has had kidney stones often gets them again in the
future. Kidney stones often occur in premature infants. Some
types of stones tend to run in families. Certain kinds of stones
can occur with bowel disease, ileal bypass for obesity , or
renal tubule defect