Kidney stone is a hard object that forms in the kidneys. Kidney stones range in size from microscopic to about as large as a golf ball. They occur primarily in men and can cause intense pain if they become stuck in the urinary tract. Most kidney stones consist of calcium salts. In many cases, doctors cannot determine why the stone forms. Some people who develop kidney stones absorb an unusually high amount of calcium from their diet. Excess calcium is eliminated in the urine. However, some of the calcium may crystallize before it leaves the body, forming a stone.
Most kidney stones pass out of the body with the urine, often accompanied by severe pain. When a stone becomes stuck, it may need to be removed by a doctor. In some cases, the doctor can remove it by inserting a flexible tube into the ureter (tube that carries urine from the kidneys to the bladder). Doctors also may use a laser or a machine called a lithotripter to treat kidney stones. In laser treatment, an optical fiber–a thin thread of glass or plastic–is inserted into the ureter until it reaches the stones. The laser then produces a beam of energy that travels through the fiber and breaks the stones into fragments, which are eliminated with the urine. A lithotripter focuses shock waves on the stones while the patient sits in a water bath. The shock waves break up the stones.
