Hypertension, calcium metabolism, and nephrolithiasis.

Alterations in calcium metabolism have been detected in both human and rat primary hypertension at various levels of the biological organization; in particular, an abnormal renal electrolyte handling, leading to chronically enhanced urinary calcium excretion, has been demonstrated. In keeping with this finding, a significant statistical association between high blood pressure and prevalence of nephrolithiasis has been found in three independent population-based surveys. The first was carried out in the early 1960s in Goteborg, Sweden, on 895 50-year-old men, and showed a higher frequency of a positive history of nephrolithiasis with increasing blood pressure. The second and third studies were performed in Italy, one in the town of Gubbio, with screening of a representative sample (n = 3,431; 84%) of the adult population and the other in Pozzuoli, Naples, at the Olivetti factory, where 688 male workers (88% of the total male workforce) were examined. In both studies, the retrospectively evaluated relative risk of nephrolithiasis in hypertensive persons, after controlling for age, was significantly higher than in normotensive persons, with hypertension contributing by 18% to the overall rate of nephrolithiasis. Hypercalciuria is the most common risk factor for nephrolithiasis and, therefore, also a likely pathogenetic link between nephrolithiasis and hypertension. Dietary factors play an important contributory role in the prevention and treatment of these two widespread conditions, and a dietary approach, with particular regard to electrolyte intake, is a powerful tool for the prevention of hypertension-related kidney stone disease.