Kidney stones form when there is a decrease in urine volumen 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. Other chemical compounds that can form stones in the urinary tract include Uric Acid and the amino acid cystine.
Dehydration from reduced fluid intake or extreme 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 infections ; these are known as struvite or infection stones.
A number of different medical conditions can lead to an increased risk for developing kidney stones:
- GOUT results in chronically increased amount of uric acid in the blood and urine and can lead to the formation of uric acid stones.
- (high calcium in the urine), another inherited condition, causes stones in more than half of cases. In this condition, too much calcium is absorbed from food and excreted into the urine, where it may form calcium phosphate or calcium oxalate stones.
- Other conditions associated with an increased risk of kidney stones include hyperparathyroidism, kidney diseases such as renal tubular acidosis, and some inherited metabolic conditions, including cystinuria and hyperoxaluria. Chronic diseases such as diabetes and high blood pressure (hypertension) are also associated with an increased risk of developing kidney stones.