Kidney Stones - Causes

Risk Factors

Kidney stones are one of the most common disorders of the urinary tract. They are an ancient health problem. Evidence of kidney stones has been found in an Egyptian mummy estimated to be more than 7,000 years old.

An estimated 1.3 million Americans seek medical help for kidney stones each year. At this time, studies suggest kidney stones affect over 5% of Americans and that the rate has increased since the 1970s, perhaps because of increases in animal and dietary protein intake.

Gender and Age

Men. The risk of kidney stones increases in a man's 40s and continues to rise until age 70. Caucasian men are at higher risk than other groups.

Women. The risk of kidney stones peaks in a woman's 50s. In younger women, stones are more likely to develop during the late stages of pregnancy. Pregnant women tend to have a higher calcium intake, but their kidneys do no handle the calcium as well as they did prior to pregnancy. Kidney stones are still a rare occurrence during pregnancy, however, affecting only 1 in 1,500 pregnancies.

Risk Factors in Children. Stones in the urinary tract in children are usually due to genetic factors. Most of the time, the cause is excess calcium in the urine (hypercalciuria). Deformities in the urinary tract pose a significant risk for kidney stones in children. Children with low birth weight who need to be fed intravenously are also at risk for stones.

Obesity and Weight Gain

Obesity and weight gain are both associated with an increased risk of kidney stones.

• Men who weigh more than 220 lbs are 44% more likely to develop kidney stones than men who weigh less than 150 lbs.
• Women who are obese are 90% more likely to develop kidney stones than women with a lower body mass index (BMI).

Higher BMIs and larger waist circumferences are both risk factors for kidney stones. Researchers think that there may be a link between fat tissue, insulin resistance, and urine composition. People with larger body sizes may excrete more calcium and uric acid, which increase the risk of kidney stone formation.