Hypertension is Associated With Increased Urinary Calcium Excretion in Patients With Nephrolithiasis

Purpose

The epidemiological relationship between nephrolithiasis and hypertension is well-known. Patients with hypertension are at increased risk for nephrolithiasis and those with nephrolithiasis are at risk for hypertension. Urine calcium or urine citrate may be related to hypertension status. We examined the relationship between hypertension and 24-hour urine composition in patients with nephrolithiasis.

Materials and Methods

We retrospectively reviewed the database on 462 stone forming patients to examine the relationship between hypertension and 24-hour urine composition. Multivariate linear regression models were adjusted for age, race, gender, body mass index, diabetes mellitus and 24-hour urine constituents. Nominal logistic regression was also done to examine the hypertension prevalence by quintile of calcium and citrate excretion.

Results

On adjusted multivariate analysis compared with normotensive stone formers those with hypertension excreted 25.6 mg per day more urine calcium, corresponding to a 12% increase in urinary calcium excretion. The relative risk of hypertension was significantly associated with quintile of calcium excretion but not with quintile of citrate excretion (1.29, 95% CI 1.02 to 1.61 vs 0.94, 95% CI 0.78 to 1.14).

Conclusions

In stone formers hypertension was associated only with significantly increased urine calcium. This association is important when treating patients with nephrolithiasis since those with hypertension may require unique dietary and medical therapy.

Key Words: kidney, nephrolithiasis, hypertension, calcium, citric acid

Abbreviations and Acronyms: BMI, body mass index, CaOx, calcium oxalate, CaP, calcium phosphate, SS, supersaturation