Kidney Stones - Risk Factors

Highlights	Risk Factors	Other Treatments
Introduction	Diagnosis	Resources
Complications	Treatment	References
Causes	Prevention
Symptoms	Medications

Risk Factors

Kidney stones are one of the most common disorders of the urinary tract, and are an ancient health problem. Evidence of this disorder was 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 prevalence has increased over the past three decades, perhaps because of increases in animal and dietary protein intake.

Gender and Age

Kidney stones affect about 12% of men and 5% of women by the time they are 70 years old.

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Men. About 80% of kidney stone sufferers are men between the ages of 20 and 50 years. Caucasian men are at higher risk than other groups.

Women. Kidney stones that strike women are more apt to occur during pregnancy, usually in the late stages. During pregnancy, women tend to have a higher calcium intake and at the same time their kidneys handle calcium less efficiently. 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 and most are caused by excess calcium in the urine (hypercalciuria). Anatomic abnormalities 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, and the risk is greatest for women. Obese 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.

Family History

People with a family history of kidney stones are at higher risk than those without relatives with stones. In one Italian analysis of kidney stone patients, 22% of their parents and 14% of their siblings also had one. Researchers are looking into markers or other factors that might predict the onset of stones in relatives, though none has yet been clearly identified. One report found that among the siblings of patients with calcium stones, sisters with higher urinary calcium levels and more acidic urine were more likely to develop stones, whereas brothers with high urinary calcium, low urinary potassium, and older age were more likely to have the problem. A family history of gout may also predispose a person to stones.