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- Kidney stone facts
- What is a kidney stone?
- Who is at risk for kidney stones?
- What causes kidney stones?
- What causes kidney stones? (continued)
- What are the signs and symptoms of kidney stones?
- How are kidney stones diagnosed?
- What is the treatment for kidney stones? How long does it take to pass a kidney stone?
- Can kidney stones be prevented?
- What is the prognosis for kidney stones?
What causes kidney stones?
Kidney stones form when there is a decrease in urine volume and/or an excess of stone-forming substances in the urine. The most common type of kidney stone contains calcium in combination with either oxalate or phosphate. A majority of kidney stones are calcium stones. Other chemical compounds that can form stones in the urinary tract include uric acid, magnesium ammonium phosphate (which forms struvite stones; see below), and the amino acid cysteine.
Dehydration from reduced fluid intake or strenuous exercise without adequate fluid replacement increases the risk of kidney stones. Obstruction to the flow of urine can also lead to stone formation. In this regard, climate may be a risk factor for kidney stone development, since residents of hot and dry areas are more likely to become dehydrated and susceptible to stone formation.
Kidney stones can also result from infection in the urinary tract; these are known as struvite or infection stones. Metabolic abnormalities, including inherited disorders of metabolism, can alter the composition of the urine and increase an individual's risk of stone formation.