The most common types contain calcium salts. They begin in the kidney as very tiny grains, but can grow to more than an inch in size. The causes of kidney stones are not always clear. Diet and fluid intake appear to be major factors.
Stones seem to be more common in hot climates and during summer months.
They are more common in people who live in the southeastern region of the United States. This may be because hot weather leads to loss of body fluids. It may also be due to regional diet. People with gout can have kidney stones made from uric acid. Stones are more common in men than in women.