In most cases there is no known reason why a kidney stone is formed. A stone can form when substances such as calcium, oxalate, cystine or uric acid are at high levels in the urine. Yet stones can also form if these chemicals are at normal levels.
A small number of people get kidney stones because of medical conditions, particularly those that can lead to high levels of calcium, oxalate, cystine or uric acid in the body.
Medications used for treating some medical conditions, such as kidney disease, cancer or HIV, can also increase the risk of developing kidney stones.Kidney stonesWho is at risk?