Picture of Kidney Stone
Kidney stones are hard crystalline substances that may form in the kidneys. They may be composed of oxalate, xanthine, urate, calcium, phosphate, or cystine. The propensity to form kidney stones may be hereditary. Dehydration, a history of gout, and the use of medications that cause a buildup of uric acid are risk factors for kidney stones.
The vast majority of kidney stones are passed by the body without any intervention. Larger stones (5 millimeters and larger) are less likely to be expelled without assistance. Large kidney stones may be removed by a procedure that uses sound waves to break them into small pieces (lithotripsy) or surgically.
Text Reference: "Kidney Stones." National Kidney Foundation.