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Essential arterial hypertension and stone disease
1Institutes of Semeiotica Medica, University of Parma, Italy. lborghi@ipruniv.cce.unipr.it
Insights
Hypertensive patients have a significantly higher risk of developing kidney stones, particularly those who are overweight. Key factors include increased urine calcium, oxalate, and supersaturation of calcium oxalate and uric acid.
Area of Science:
- Nephrology
- Cardiovascular Medicine
- Urology
Background:
- Cross-sectional studies indicate a higher prevalence of nephrolithiasis in hypertensive individuals.
- The precise pathogenic link between hypertension and kidney stone formation remains unclear.
Purpose of the Study:
- To investigate the baseline stone risk profile in patients with stable essential hypertension compared to normotensive controls.
- To assess the long-term incidence of kidney stone formation in both hypertensive and normotensive subjects.
Main Methods:
- A cohort study involving 132 hypertensive patients and 135 age- and sex-matched normotensive controls.
- Baseline assessment of urine stone risk factors, including salt supersaturation.
- Minimum five-year follow-up to monitor kidney stone formation.
Main Results:
- Hypertensive males exhibited higher urine calcium, magnesium, uric acid, and oxalate levels, with greater supersaturation for calcium oxalate and calcium phosphate.
- Hypertensive females showed elevated urine calcium, phosphorus, and oxalate, with increased calcium oxalate supersaturation.
- The incidence of stone episodes was significantly higher in hypertensive patients (14.3%) compared to normotensive controls (2.9%).
- Calcium oxalate supersaturation predicted calcium calculi, while uric acid supersaturation predicted uric acid calculi.
Conclusions:
- Hypertension is associated with a substantially increased risk of renal stone formation, especially in overweight individuals.
- Elevated urinary calcium, oxalate, and supersaturation of calcium oxalate and uric acid are critical factors in stone development.
- Obesity, high salt intake, and consumption of animal proteins may contribute to this increased risk.
Background:
Cross-sectional studies have shown that nephrolithiasis is more frequently found in hypertensive patients than in normotensive subjects, but the pathogenic link between hypertension and stone disease is still not clear.
Methods:
Between 1984 and 1991, we studied the baseline stone risk profile, including supersaturation of lithogenic salts, in 132 patients with stable essential hypertension (diastolic blood pressure of more than 95 mm Hg) without stone disease and 135 normotensive subjects (diastolic blood pressure less than 85 mm Hg) without stone disease who were matched for age and sex (controls). Subsequently, both controls and hypertensives were followed up for at least five years to check on the eventual formation of kidney stones.
Results:
Baseline urine levels in hypertensive males were different from that of normotensive males with regards to calcium (263 vs. 199 mg/day), magnesium (100 vs. 85 mg/day), uric acid (707 vs. 586 mg/day), and oxalate (34.8 vs. 26.5 mg/day). Moreover, the urine of hypertensive males was more supersaturated for calcium oxalate (8.9 vs. 6.1) and calcium phosphate (1.39 vs. 0.74). Baseline urine levels in hypertensive females were different from that of normotensive females with regards to calcium (212 vs. 154 mg/day), phosphorus (696 vs. 614 mg/day), and oxalate (26.2 vs. 21.7 mg/day), and the urine of hypertensive females was more supersaturated for calcium oxalate (7.1 vs. 4.8). These urinary alterations were only partially dependent on the greater body mass index in hypertensive patients. During the follow-up, 19 out of 132 hypertensive patients and 4 out of 135 normotensive patients had stone episodes (14.3 vs. 2.9%, chi-square 11.07, P = 0.001; odds ratio 5.5, 95% CI, 1.82 to 16.66). Of the 19 stone-former hypertensive patients, 12 formed calcium calculi, 5 formed uric acid calculi, and 2 formed nondetermined calculi. Of the urinary factors for lithogenous risk, those with the greatest predictive value were supersaturation of calcium oxalate for calcium calculi and uric acid supersaturation for uric acid calculi.
Conclusions:
A significant percentage of hypertensive subjects has a greater risk of renal stone formation, especially when hypertension is associated with excessive body weight. Higher oxaluria and calciuria as well as supersaturation of calcium oxalate and uric acid appear to be the most important factors. Excessive weight and consumption of salt and animal proteins may also play an important role.