How Stones Form These components of urine normally remain dissolved. However, when there is not enough water to keep them dissolved or when too much of one of these minerals is present, it can crystallize to form stones.Thus, not drinking enough water is the most important cause of kidney stones. Younger people often underestimate the amount of liquids they drink while physiologic changes associated with aging make older people less sensitive to thirst.With relative dehydration tiny crystals form in the urine and may be deposited on the inner surface of one or both of the kidneys. Stones are formed as crystals combine together. 70% to 80% of all kidney stones are composed of calcium oxalate. Decreasing calcium intake is no longer recommended by doctors because we now know that oxalate is the main culprit. Current recommendations for those susceptible to kidney stones are to maintain normal calcium intake but to cut down on oxalate rich foods and avoid excess vitamin C (excess vitamin C is converted to oxalate). Other causes of kidney stones In addition to lack of water combined with an oxalate rich diet include:

Excess vitamin D (more than 1 gram per day) and/or Vitamin C (more than 200 milligrams per day)

Prolonged immobilization (bed rest) causes the release of calcium from bones

Hyperparathyroidism- increases the amount of calcium in the blood

Less common types of stones include :

Uric-acid stones- seen in persons with gout

Struvite (triple phosphate) stones- seen in persons with chronic urinary tract infections. These stones may be quite large

Cystine stones- seen in children with a disorder of metabolism