12 of men and 5 of women of Western European descent develop at least one urinary stone during their lifetime. The incidence is somewhat less in individuals of sub-Saharan African or Asian descent, although there is a high incidence in the Middle Eastern countries. Calcium oxalate is a major constituent of about 70 of these stones. They are of multifactorial origin, with both genetic and environmental factors involved. The genetic factors influence different components of a highly complex system whereby calcium oxalate, which has a very low solubility in water, remains in solution. When the system is perturbed, the calcium oxalate crystallizes, the crystals aggregate and stones form. The genetic factors operate through mechanisms that are less obvious than the environmental ones such as the patient's state of hydration and dietary effects on the concentrations of the relevant ionic species.
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